Abrupt Change of Season

The best laid plans are no match for Mother Nature. November has been less than kind in this part of the world. November began cold and windy, then came the snow. So far we've had 25 cm of snowfall. It isn't melting. Temperatures have gone as low as -17 C with wind chills even lower. Records have fallen. One wind storm brought gusts well above 100 kph that had the house shaking. After the sun rose I saw that all the towers and antennas survived.

Some moderation is in the forecast though not what it should be. Normal highs in early November range from 8 C to 6 C. This is comfortable for antenna and tower work. My plans relied on weather that did not vary too far from the expected. Now I'm faced with this:

In the foreground is one of my new 20 meter long boom yagis. In the background is one of the 15 meter yagis. A second 15 meter yagi is buried in the snow and can't be seen. These are 3 of the 4 big yagis for my 15 and 20 meter stacks for the newly completed 140' (40 meter) high tower in the background.

The frustrating thing is that the antennas work. They've been tuned and tested. All that's needed is the permanent gamma match assemblies, mounting hardware and boom trusses. Despite progress of all of those it is unlikely that these antenna will be raised in time for CQ WW CW which is rapidly approaching.

However it is not all bleak. With a moderation in the weather (likely) the side mount yagis will be completed and raised. The tower brackets are ready to go and the tram line is in position. Most of the truss hardware is ready to be assembled. Heliax feed lines are in the midst of assembly and testing. All of it looks good.

With these pointed at Europe I will have more capability in upcoming contests. If I get lucky the mast can be raised and the rotatable yagis can be lifted onto the mast. These operations require less snow on the ground to allow a power lift: they're too heavy to be trammed by muscle alone.

My 40 meter rotatable dipole project is similarly on hold. In fact I have not assembled it although all the material is on hand. This is an impediment for chasing distant multipliers on 40 meters since I moved the XM240 from its previous 46 meter height down to 21 meters. On the positive side this antenna should not be too difficult to raise. All that will be needed is to build and tune the gamma match. The transmission line and rotation loop are ready for use.

For now I do what I can on the ground and hope for better weather. Failing that I am forced to wait until spring. Around here that means at least 5 months (April) and possibly May. June through mid-August is haying season when little work on the big towers is possible.

Thoughts on Two Keyboard SO2R

In the ARRL Sweepstakes CW contest last weekend I operated SO2R using two keyboards. This was a first for me. Several months ago I purchased a wireless keyboard and mouse so I had the keyboards ready to go.

SO2R (single operator, two radios) is used by skilled contesters to maximize their score. This comes at the expense of mental fatigue and a difficult learning curve. It is possible to practice offline with running simulators such as Morserunner, yet that is no substitute for reality, especially if you have a small station and need to S & P (search and pounce) quite a bit.

Among SO2R aficionados there are those who use one keyboard and those who use two. Both can work well, and you'll find a mix of techniques among the top contesters. The differences are many yet, I believe, can be roughly compared as follows:

• One keyboard: Less physically fatiguing since you hover over just the one keyboard. It can be more mentally fatiguing since you rely on special keys to change radio focus, carefully monitor the display to confirm radio and QSO state, enter what you hear in the correct radio window, deal with out-of-pattern situations such as requesting or responding to fills, etc. Once you become skilled the mental fatigue declines.
• Two keyboards: More physically fatiguing since you literally constantly switch between keyboards for each QSO state. Fatigue can be reduced with software features to direct commands from a keyboard to the other radio, automatic CQ, etc. With practice there is an improved economy of motion that reduces physical fatigue. Mental fatigue is lower since focus in determined by keyboard use without the needs to use and monitor radio and QSO state.

Now that I've done it I've gained an appreciation of two keyboard SO2R. My software of choice is N1MM Logger+. Some of the other popular contest loggers also support two keyboards. Because my experience is limited to N1MM my discussion of its pros and cons may not be entirely application to other contest loggers. Some of the quirks that I encountered using N1MM two keyboard SO2R may be bugs -- yet to be confirmed -- so I won't dwell on them here.

Operating desk

My operating desk for Sweepstakes was as shown below. The photo was manipulated to reduce the screen brightness, which unfortunately does not help much! Those familiar with N1MM should recognize the two entry windows at the centre bottom and their respective band maps at either side. The other windows I have open are not pertinent to SO2R.

When I use one keyboard it is in front of the display. The paddles and mouse would be on the right of the keyboard since I'm right handed. With two keyboards placing them between the keyboards worked the same for the left radio and required a bit of arm crossing when on the right radio. My manual headphone switch is behind the paddles. The manual antenna switch is on top of the right radio.

Compare this with a photo of my single keyboard setup and an explanation of my home brew headphone switch. Many operators using one keyboard, SO2R or not, persist in putting it in front of the radio and the display up above. Disadvantages include arms and hands dragging on the keyboard when operating the rig and constantly having to tilt the head up to look at the display. I keep the display low so that my head and neck stay relaxed and keep my reach to rig control unencumbered.

You have to touch the rig less than you might imagine. The exception is small stations since you must spin the VFO for S & P. With N1MM and other contest loggers there are a host of keyboard shortcuts for many rig features that, as you learn them, require far less manual control of the rigs.

Those with rigs with full software interfaces (e.g. Flex) and advanced station automation have no boxes and physical controls to deal with; the operator uses the keyboard or mouse. The typical setup for those stations is to place two or monitors side by side. For SO2R with two of these rigs there would be two PCs and therefore two keyboards. SDR rigs with two slices can share one PC and one keyboard.

Which is better for the SO2R novice?

As already mentioned, many of the top contesters continue to do SO2R with one keyboard and suffer no deficit in their results. For the experienced contester who is a novice at SO2R the choice can make a significant difference. Having tried both my tentative conclusion is that two keyboards is the better choice for the SO2R novice.

The major challenge with single keyboard SO2R is the steep learning curve. There are many balls to juggle and quite a few mistakes will be made. Although the software will usually put the typed call and exchange in the correct window each radio's QSO state and software focus must be constantly monitors and keys pressed to change focus as needed. Alternatively you can explicitly send commands to the opposite radio. Keeping it all straight takes practice, a lot of practice.

With two keyboards you can get started and be quite productive with far fewer critical operations to remember and use. Rather than change focus or direct commands you simply manipulate the keyboard associated with the desired radio. This comes at the cost of swivelling more in your chair and its attendant latency.

Another aid for novices is to use low power or even QRP as I did during Sweepstakes. The lower rate and lower value of dual CQing keeps the stress to a minimum. There will be fewer moments of intense activity. Another suggestion is to try SO2R in small and regional contests (e.g. QSO parties) where the activity level is lower or intermittent. By keeping the stress low while you learn you'll have more fun as you hone your skills.

Once you get the basics mastered you still have access to and can use keyboard controls to direct commands to the other radio. For example, to repeat an exchange on the other radio you can direct a command (CTRL-F2 in this case using N1MM) from the same keyboard you are entering info you are copying on the other radio. By cutting out some of the swivelling you reduce fatigue as your skills improve.

In time you may opt to switch to single keyboard SO2R. Choose which works for you. My suggestion is to try both rather than assume that one or the other is better. Keyboards are cheap and you probably have a spare collecting dust.

Go with wireless keyboards to reduce demand for limited USB ports (hubs don't always work well) and fewer opportunities for RF to get into the PC and cause glitches.

Plans going forward

I plan to replace the operating desk to be more contest friendly. It has to be longer to accommodate two operator positions (multi-op contesting), no drawers to bang knees into and reduce operator reach and have multiple levels to keep ancillary equipment within easy reach. As automation is deployed there will be less need for ancillary equipment, such as manual antenna switches, or the functions will be moved to software (PC control of rotators, antenna choice, etc.).

Because the keyboards make it more difficult to control buttons and dials a popular solution is to raise the rigs on a low shelf. There is less risk of accidental key presses when reaching for the rig. In some designs the keyboard can slip underneath the rig when not in use. Desk clutter is reduced when the station isn't being use.

Another shelf above the rig can support manually tuned amplifiers to keep them in easy reach to tune them after band changes, and for frequency and antenna changes within the same band.

Since the layout for two keyboard SO2R is similar to that for two operator multi-ops there is less work to do before and after the contest. Rotate a few boxes, roll up another chair and you're pretty well ready. The need for a second PC and display(s) will initially increase the complexity of transitions until the process becomes routine. The greater the degree of automation the fewer the items that must be rearranged.

Over the winter my shack plans will be refined. I'm not sure how much I'll actually do this winter except that I do want to be multi-op ready so that I can invite my friends over for contests. An effective SO2R station is a step along that path.

I consider myself an SO2R novice and I will keep practicing in contests and evaluating alternative station configurations.

QRP for the FTdx5000

After selling my Elecraft KX3 earlier this year (as planned) I was left with one rig that could be dialled down to 5 watts for entering contests in the QRP category. That rig is a Yaesu FT950, a rig with very dated technology. It used to me my main transceiver for most operating. Although I still enjoyed using the KX3 its use was solely for QRP contest entry after returning to using higher power.

Because its receiver is quite poor I avoid the FT950 other than as a second radio for SO2R contest operation. Until I upgrade shack equipment to be more contest friendly I use it to practice SO2R. Eventually it'll be replaced.

My main rig is an FTdx5000. This 200 watt transceiver cannot be reduced to QRP power level. Its minimum setting is 10 watts. The problem was that I intended to enter the ARRL CW Sweepstakes contest in the QRP category this past weekend. I couldn't bear the thought of using the FT950 all weekend.

I also wanted to improve my modest SO2R skills. This contest is great for that since the pace is more measured and with QRP I don't have high hourly rates beyond the first few hours. I also wanted to improve on last year's score when I might have won had I operated full 24 hours.

My objectives meant borrowing a transceiver or fitting the FTdx5000 into a QRP box. I opted for the latter. Aside from what ought to be the obvious solution that I eventually selected a few other paths were investigated:

• Class A: Running the transmitter in low distortion and low efficiency class A reduces the maximum power to 75 watts. It turns out that adjusting the power does not proportionately decrease the power by ⅝ at all level. If you set the power to 10 watts you still get 10 watts, but a supposedly very clean 10 watts.
• External ALC: There is a negative feedback port on the rear panel to allow an external amplifier to dynamically reduce the power level when it is over-driven. I tried it with a AAA battery in reverse polarity -- the port accepts from 0 to -4 volts. Nothing happened. An internet search didn't solve the puzzle. E-ALC was ruled out since time was running out.
• Lossy coax: Unfortunately I had none suitable that I could connect. In any case the loss would be frequency sensitive.

Not surprisingly I went for the brute force solution: an RF attenuator. It's a simple project that took me only two hours to whip up in the workshop. It has just a few design parameters:

• Knock 10 watts down to 5 watts from 1.8 to 30 MHz.
• Dissipate 5 watts of heat, preferably with 100% duty cycle for ultimate robustness.
• Good impedance match to 50 Ω.

The circuit diagram for 3 db attenuators with 50 Ω ports is easy to find. Calculation is more difficult. From an old ARRL Handbook the series resistance is 18 Ω and the parallel resistance on each port is 300 Ω. These are exact or close to standard resistor values so I went digging in my junk box for suitable candidates. Then it was off to my workshop.

Before visiting the junk box I did some calculation to determine that most of the power dissipation is in the parallel 18 Ω resistance. This isn't surprising since it is by far the lowest resistance in the network, ports included. I didn't bother figuring out the exact dissipation values since close is good enough for this application and solving resistor networks isn't fun.

Construction is incredibly simple. The biggest job was punching the ⅝" holes for the SO239 panel jacks. I used the cheapest jacks I had on hand. The box is new from my stock of plastic and aluminum boxes that I keep on hand for home brew projects.

Although simple there are a few points worth mentioning:

• The box should be conductive to prevent RF leakage in and out and to minimize frequency sensitive impedance variation.
• The wire between the jack shells further improves high frequency performance. It's better than solely relying on the enclosure. Notice the short leads of the parallel resistors the wire makes possible.
• Carbon composition is the best choice with carbon film close behind. For HF use other resistor types can be used but never use wire-wound resistors.
• Resistance values can be achieved with multiple resistors in series or parallel. With the help of an ohmmeter you can get very close to the exact values. Resistors often deviate from the specified value (pay attention the tolerance colour band) so try them all. Multiple small size resistors can have the power dissipation rating of a single high power resistor which is less likely to be found in the junk box.

After soldering it together I plugged my antenna analyzer into one port and a 50 Ω load into the other and swept the HF spectrum. It's very flat with a maximum SWR below 1.1 up to 30 MHz. I didn't test it at 6 meters and above.

The final test was to connect it to the rig and place watt meters at each port. Since I have only one standalone power meter I relied on the rig's PO meter for the transmitter port. Power was reduced to 10 watts and tested at a few frequencies.

The result was very good. Since power meters are often inaccurate I compared the meter reading with what I recall from using my KX3 at 5 watts. Both readings are a whisker above the 5 watt tick. The difference expressed in decibels would be exceptionally small. In any case the true output of any transmitter is never as precise as suggested by the digital display.

As a further test I opened the box and ran the transmitter with a solid 10 watt carrier for a few minutes. There was no smoke coming from the resistors nor was there obvious heat radiating from them. The series resistor pair was a little warm.

There are a few items to keep in mind when operating with an attenuator of this type:

• If your rig has a physical power level control it is easy to forget the attenuator is there after you're done with a QRP event. Transmit at 200 watts and you'll have to replace all the ruined resistors. Look for the software parameter to limit the maximum power to the lowest setting. On the FTdx5000 that is 20 watts. The attenuator will survive dissipating 10 watts.
• Receive strength is reduced by 3 db. On HF you may not notice, more so during the present solar minimum when you are not often on 10 or 15 meters. If it's a problem increase the rig's pre-amp setting. Modern receivers have an abundance of pre-amplification features.
• You don't need a tuner! The increased return loss due to the attenuator greatly lowers the mismatch seen by the rig. For example, my poorly adjusted 80 meter inverted vee has an SWR of close to 3 at 3500 kHz and requires the ATU. With the attenuator the SWR was not much worse than 1.2 so the ATU was switched off throughout the contest. 
• Despite the low SWR seen by the transmitter the SWR at the antenna port is unchanged. Large deviations from 50 + j0 Ω will change the attenuation level to a value lower or higher than 3 db. For high SWR you should use a tuner between the antenna and attenuator to be certain that you are below the QRP power limit.

The attenuator worked perfectly during Sweepstakes. I was going to discard it afterwards (recycle the components) then reconsidered since there are other contests in which I'd like to have the option of operating QRP. One possibility is the Stew Perry TBDC on 160 meters this winter. I'll keep it around.

Hy-Gain Trap Repair

Traps on Hy-Gain HF yagis are not really designed to be serviced by users. Of course we're hams so we do it anyway. Despite a lot of disparagement of traps including those of Hy-Gain yagis they can be effective performers. With the wide availability of inexpensive Hy-Gain yagis on the used market many hams will find themselves with a good tri-band yagi that has been in the air some time and may need some repair. The traps are usually the only daunting aspect of the job.

I purchased my TH6 and Ham-M rotator from a local ham back in 1985. At that time it had been on his tower for at least 10 years. In those early days the hardware wasn't stainless steel so much of that had to be cut off and replaced. The dreadful BN86 balun that comes with the antenna was soon discarded in favour of a coax choke. A couple of the traps needed service and I puzzled out their disassembly and repair -- I couldn't benefit from an internet search back then.

When done it performed flawlessly until 1992 when I dismantled the tower and antennas and exited amateur radio for over 20 years. I kept the antenna, and indeed I sold very little of my equipment in the intervening years. I restarted in the hobby in 2013 in a small way, gradually increasing the size of the antenna systems. The driven element was put to use as a trap dipole for a short time.

In 2017 the antenna was refurbished and raised to the top of my new 150' tower. A couple of mechanically suspect traps were given cursory attention since it was the onset of winter and time was of the essence. Trouble reared its head the next winter. I had planned to have it up there for no more than 6 or 8 months but changed plans meant leaving it up there another year. Hope is a poor strategy for ensuring antenna reliability.

Again I failed to repair the suspect traps when I had it on the ground this fall. It went intermittent during CQ WW SSB this past weekend. This time I would have to take action. It was a simple matter to isolate the problem. With an antenna analyzer attached I wiggled the elements within reach of the tower. The SWR bounced around when one half of the driven element was shaken. The trap itself wiggled which made the failure point obvious. It was a simple matter to pull the half element out and lower it to the ground.

Trap structure

Hy-Gain yagi traps are not designed to be opened and serviced. Of course countless hams, myself included, do it all the time. The first time a trap is opened it is difficult to separate the parts without causing damage if you are unfamiliar with how they're built. A mistake usually makes it unusable. It is worthwhile to learn how to do it properly if you insist on doing repairs yourself.

The first thing to know is what's inside: the components and how they're put together. All the Hy-Gain traps for the tri-band yagis are the same no matter the model, be it an ancient TH6, a relatively recent TH11, a TH3, an Explorer 14 and so on. Indeed there are only 4 traps for the tri-band yagis:

• 10 meters: there is a different version for parasitic elements on some yagis
• 15 meters, for directors and reflectors
• 15 meters, for the driven element

They are mostly distinguishable without the part numbers printed on the outer body, which is a good thing since the labels fade with age. The 10 meter traps are shorter than the 15 meter traps, the 10 meter and 15 meter parasitic element trap coils are wound with aluminum wire, and the 15 meter driven element trap coils are wound with copper wire.

Compare body lengths and peek in the weep holes and you have all the data you need to identify the trap. That said, I haven't directly compared the two versions of the 10 meter trap. Hy-Gain sells new traps at a reasonable price, and even most of the component parts. That's an alternative to repair. Go to their web site and search for "trap".

I pulled a broken 10 meter trap from my antenna junk box that I scavenged from another ham's antenna nightmare. The coil form and tab connecting the shell (capacitor) to the right tube are broken. I don't know the story of how it broke. Laying out the pieces as I've done gives an idea of what's inside. These traps are really very simple devices and quite robust when not abused in service, disassembly or reassembly.

The three sheet metal screw that secure the coil end and the shell tab are frequently criticized. While not a superb choice the screws are tough and have an integrated lock washer, and when the traps are properly assembled the screws are under very little stress. I judge the design a reasonable compromise between cost and robustness. The trouble comes when the traps are reassembled after service.

The plastic spacers are critical to the strength of the trap. Install them incorrectly and fatigue failures will occur. Their purpose is to keep the inner tube and coil rigid with respect to the outer tube. Since the weakest component is the coil (wire and form) these must not flex under wind and ice loads. When the spacers are properly positioned flex is minimized. It takes two spacers on either side of the coil to prevent the inner tube from flexing.

The inner end of the 10 meter traps (on the right, with the tab) flex the most since the spacers are close together. Over the years the tab can fatigue and break. This is usually only a problem on the driven element since the larger and heavier 15 meter trap on the outer end of the element increases stress on the 10 meter trap.

The spacers are positioned correctly when manufactured. Dimples (small depressions) in the shell hold the spacers in place. There are cavities in the spacers that align with the weep holes so that the spacers don't dam water flow.

To disassemble the trap remove the screw on the shell tab and push the inner tube left with respect to shell as oriented in the picture above. Some force may be needed to push the two left spacers over the dimples. Unfortunately the spacers may suffer some damage but there's no good alternative to getting them out. The spacers on the right will most likely stay where they are during disassembly and reassembly.

To reassemble the trap you push the inner assembly in from the left of the shell. If the rightmost spacers moved reposition them first. The one on the outside comes close to the tab. The other should be pushed from the left to its approximate position. Use the dimples as a guide but don't obsess over getting it perfectly aligned. But do try to have a weep hole aligned with the outer tube weep holes.

Even it isn't in far enough the trap coil screw push it further when it is inserted. Avoid this if possible since is a small risk of damage to the spacer and coil. If the spacer is too far outboard use a blunt metal rod to lightly tap it toward the coil through the outermost spacers weep holes, going around from hole to hole so that it doesn't jam. The most common reason for the spacer to be too far outboard is pushing the inner assembly too far to the right. Move slowly and watch for the tab screw hole to appear. Screw the tab to the inner tube.

Push a spacer in from the left until it is at or near its dimple on the left side of the coil. Hold the outer tube in a non-marring vice while for best control and least risk of damage to the tab. A 1" PVC pipe can be used to slide over the inner tube and apply even pressure to the spacer. Don't push it in too fare (right up against the coil) or you'll have start over again.

Finally insert the leftmost spacer and you're done. Hold each end of the inner assembly check for flex. There should be little to none. Remember to slip on the trap covers. I wrap the covers with Scotch 33+ for extended UV protection. Replacements are cheap if you need them.

Repair

For my repair job I disassembled the 10 meter and 15 meter traps. Although only the 10 meter trap was flexing I chose to do both since I had them in hand.

No wire breaks or loose hardware were evident. This can be a problem when the traps are mechanically unstable because the coil wires or forms will flex and eventually break. There was no damage of this kind just some debris and corrosion. An old insect nest was removed.

I undid the screws at either end of the coils and lightly sanded the aluminum surfaces to ensure good electrical contact. The inner end of the 10 meter trap tube was slightly distorted by the flexing so I pulled it from the coil form and gently applied pressure to the tube with a vice to reduce the freedom of motion it had developed. Perhaps a needless repair but I prefer that the form fit snugly.

As expected the spacers were out of position and that is what caused the flexing. The spacers were correctly positioned (as described above) during reassembly. The half element was then put back together and the dimensions checked. The entire job took less than 2 hours despite proceeding carefully. I wish that I'd taken the same care the last time I did this job!

Back in the air

For late October the weather was warm so I rushed to put the driven element back together before the weather turned. The high wind that day didn't dissuade me since the half element is easy to lift. I stuffed it and the insulator back into the boom clamp and attached the clamp and wires going to the balun and hairpin (beta match shorted transmission line stub). Within minutes I was ready to test my repair.

The element no longer wobbled when shaken. I connected the antenna analyzer to the balun and the SWR was what it ought to be. So far so good. To my dismay the SWR again misbehaved when I wiggled the driven element in exactly the same fashion as before the repair. That was not good. Although the poorly assembled trap need fixing the problem was evidently elsewhere.

Oops!

Further troubleshooting showed there were two problems not one. The first was found by wiggling every wire and connection on the balun, driven element and hairpin stub. The wire from the stub to the clamp on the suspect half element was intermittent.

It seems that after 45 or 50 years the stranded wire had few intact strands remaining. Nothing lasts forever. I now realize that this was the same intermittent problem that developed earlier when the antenna was on top of the 150' tower.

Hy-Gain yagis of that vintage did not use stainless hardware. The screws and nuts are pretty well welded onto the aluminum tubes of the stubs. Since I was not prepared to tram the antenna to the ground to destructively remove the hardware I used a hose clamp to attach the new wire to the tube.

The wire quality is not the best but it should hold through the winter. I put a few layers of tape on the wire insulation where it might touch the boom clamp for added protection from high voltage and stray capacitance.

Finally the antenna survived the wiggle test. The SWR tests perfectly on all three bands.

The next problem was further down the tower. Where the short length of RG213 from the antenna to connects to the long length of Heliax the UHF to N adaptor was visibly bent underneath the layer of weatherproofing. Although the SWR was fine in the shack this could not be left as is due to risk of imminent failure.

The Heliax terminated with a male N and the RG213 had a male UHF. Adaptors with an N female on one end and a UHF female on the other end are rare. The 10 meter length of RG213 I grabbed from my junk box had a heavily taped N female on it that looked perfect for what I needed to hook up the newly side mounted TH6.

When I cut away the layers of plastic and rubber I discovered the problem. This old bit of coax was older than I realized. Inside was an adapter I home brewed back in the 80s for LDF4 runs, all with N male terminations.

Oh, to be young and foolish again! Unwrapping this contraption brought back memories. The shells of the N female and PL259 reducer were merely pressed together. It had no mechanical strength at all. I'm surprised it lasted as long as it did. Only the tape holding the halves together allowed for electrical continuity.

The abomination was replaced with an N female barrel connector and a more common N male to UHF female adapter. I have both in abundance since I routinely connect Heliax main runs to RG213 and LMR400 terminations. I taped up the joints and this time I really did had the problem resolved.

Rush jobs coming up

The weather is finally turning colder, windier and wetter. Time to finish the many antenna jobs I have ongoing is running out. Just this week I found time to (finally!) complete my 80 meter vertical yagi. An article on that should be out next week. The 20 meter and 15 meter stacks are slowly progressing, with two yagis tested and working. I am rebuilding the boom of the upper 20 meter yagi so that it is stronger and lighter. Permanent gamma matches to replace the testing/tuning gamma matches are under construction. Other hardware to side mount and mast mount the yagis has recently arrived or will be fabricated shortly.

The time taken to repair the TH6 delays every other job making this problem very unwelcome. The antenna was really proving its worth during CQ WW SSB before it quit working. As the number of towers and antennas grows the probability of a problem arising increases. Problems come in all types. For example, this week I discovered a small pit dug into the bundle of Heliax and other cables running from the 150' tower. Some animal, probably a skunk, dug up a wasp nest that was down there. I inspected the cables -- thankfully there was no damage -- and refilled the hole.

Maintenance is never ending in a growing antenna farm. I am spending some time on the air, entering contests and working DXpeditions. I count myself fortunate to have the time to do all of this and for the friends willing to help even when the weather is unpleasant. They seem to enjoy being a part of this journey.

However it is better to do things right the first time and avoid unwanted repair jobs.

Tower Lift Failures - Are You Prepared?

First the good news. My new 140' tower is complete. At the time the adjacent photo was taken the only thing left to do was to tighten the top set of guys and realign the tower. There are no antennas on the tower at this point. A few of the yagis for the 15 and 20 meter stacks can be seen on the ground biding their time.

The reason I delayed completing the tower was to build the mast and rotation system which required keeping the top two sections on the ground. With that job completed the tower sections could be raised. More on that in a subsequent article.

Unfortunately the final lift was not without mishap. No matter how carefully you plan and execute an operation of this scale there is an ever-present possibility that something will go wrong. It is never routine.

Several of the hams who have generously given their time to this project have commented that I make these big jobs look easy. Of course they are not easy. It helps to have experience but that is no insurance policy. What experience does provide is a bag of tricks to avoid or recover from many of the things that can and do go wrong.

No one was injured and the toll on tools and equipment was minor. I enforce safety practices on site. By describing what happened and what may have precipitated the mishap I hope to instill a sense of respect in readers for towers big and small. Mistakes can be very costly.

Photo credit: all but two of the pictures in this article are courtesy of Alan VE3KAE who was assisting me that day.

Lift procedure

Like most hams I don't do tower lifts the way professionals do it. The cost of tools, equipment and manpower is too high and unjustified for a ham. For those without the ability to do the work it is worthwhile to hire those professionals. I won't say more about how they do these jobs.

Hauling 150 lb loads 150' vertically upward is not a job for a few muscular hams. A manual winch with a 4:1 or greater advantage isn't as easy as you might guess, and it takes a long time. Power is required. A vehicle or tractor comes in handy and I've used both over the years.

A pulley at the tower based turns the downward rope from the gin pole horizontal. Find a suitable attachment point (tow hook, trailer hitch, etc.), hook up securely and without risk to the vehicle and away you go. The biggest problem is that you have more power than needed. An automatic transmission with a hydraulic clutch helps modulate the power. A rope rather than steel cable provides elasticity that allows a safe and graceful recovery when the load inevitable snags a guy or other tower protrusion.

Failure

When the tower section was up about 90' the rope seized. The load would not move up or down. A brief inspection discovered that wheel on the bottom pulley had split in two. The rope was caught in between the broken halves and was partially severed.

No disaster at that point but not an easy problem to resolve. The axle kept the rope from popping out and dropping the load. Had it broken through the load would have dropped at least 40' and possibly hit a guy at the 65' level. Damage to the car was likely. Had the rope been severed the load would have gone into free fall, an even worse outcome.

Since the situation was stable I had a few minutes to consider the problem. We took care to stand to one side of the tower while doing this. Had the rope or axle broken we would have had time to jump away from ground zero. Hard hats and steel toe boots are no match for a free falling load.

Unfortunately there is no picture of the seized and broken pulley since we were fully occupied dealing with it. The picture shows the split wheel and axle after being extracted from the pulley during the recovery procedure.

Recovery

As the saying goes: necessity is the mother of invention. The come-along (hand winch) and a bunch of old guy grips were at hand in preparation to pull in the top set of guys. While a poor fit the grip was wrapped on the top side of the rope, a thimble inserted and the the come-along hooked to the tower bottom.

Once the tension was transferred the load was safely suspended. The pulley was then broken apart and the rope freed.

A new and larger pulley was attached next to the old one on the same cable wrapped around the tower base. The rope was wrapped around the pulley wheel and the pulley was reassembled. Only then did we pause to have a close look at the rope cut.

No more than 25% of the rope fibres were severed. It still had ample capacity to support the load. The car was backed up to take up the tension and test this assessment. Had it broken through the come-along would have held the rope.

The rope was again inspected under load. We decided to continue the lift with the damaged rope and new pulley.

Completion

The lift was completed without incident. Before climbing up the come-along was reattached to the rope. This eliminated further risk from the damaged rope. My helper used the come-along to lower the tower section into place when I was in position.

The two pictures were taken at almost the same moment. Alan took the one on the left -- one of the rare pictures of me in this blog. You can see me retrieving or replacing my phone for the picture on the right.

Notice that the gin pole has taken some abuse during this problem plagued lift. It looks bad but all that happened is that the pole rotated and pivoted on the top pin so that it is no longer perfectly vertical. This has happened before and is not a risk. All that said it is safer for the rigger to be at the top before the lift, staying above the load rather than climbing below it. On that day the ideal wasn't attainable.

After clearing the tower top the load typically dangles on the far side of the gin pole, only occasionally drifting in the breeze to where you see it in the pictures. The tower has only one climbing face so I cannot climb another face as the load drifts. We monitor it in case something untoward occurs.

A few minutes after reaching the top the section was lowered and bolted in. The guys were then lifted and attached to the segments on the top section. Success at last. After a break we pulled the guys to the anchors and called it a day.

Aftermath

Equipment doesn't come with a best before date. Everything should be inspected before an operation. Had I looked closely at the pulley it's possible I'd have seen something. Often the damage isn't visible so you must rely on the quality of the hardware.

The pulleys have seen lengthy service: lifting 300' of tower; tramming yagis; and a variety of other heavy lifts. Each has passed many thousands of feet (or meters) of rope and cable. No equipment lasts forever, not even when the working load capacity is never exceeded. Since an identical pulley is on the gin pole I brought it down and inspected it. Unlike the broken one there is no evidence of stress. Despite that the pulley will no longer be used at critical locations for heavy loads.

The 100 meter long polypropylene twist rope is approaching end of life, and that's okay since I planned to discard it once the tower was up. There is UV damage (polypropylene is very sensitive to UV) and fraying. Considering what I paid for it I have no complaint. I'll can buy another reel of it or a better product.

I subsequently spoke to a local tower pro. He showed me the rope and pulleys they use. These are very expensive and look awesome. I found it interesting that they never use steel cable, only rope. I will hunt for suitable products at a better price point.

For critical lifts I will be more diligent about using keepers. These are loosely bound ropes or cables that "catch" lifting ropes should the hardware fail. For example, a keeper for the recent failure would be a cable around the tower pillar that passes on the outside of the pulley. Even if the rope comes completely free the load will not fall. Unfortunately the mechanism to recover from a severed rope is not so easy to implement. The answer to that is to use better rope.

As to why the pulley wheel failed I have a likely failure mode. These pulleys are made for rope. As the loaded rope passes over the wheel it compresses and spreads the load over a large cross section of the wheel surface. Steel doesn't behave this way. Since it is thinner (for the same capacity) the force is focused on a narrower area of the wheel.

Second, aircraft cables are hardened steel that abrade the wheel surface, thinning it and reducing its load capacity. Steel cable should not be used on rope pulleys or the pulleys should be discarded sooner and inspected before each use. In future I will try to avoid steel cable for lifts and tram lines. The former I haven't done for a long time anyway.

None of us is perfect. By dissecting this mishap I hope to provide a lesson to myself and to others. Learning by direct experience alone can be deadly. Be safe out there.

Low Band DXing: You Snooze, You Lose

Those who have been reading this blog lately will know that I've been very busy lately with tower and antenna work. That time mostly comes from that devoted to operating so that the rest of my life isn't impacted too much. However there are many DXpeditions this month that do entice me to make an occasional effort.

One of those DXpeditions was ZK3A Tokelau. Although I have ZK3 worked and confirmed I wanted to log it on the low bands where it is a new DXCC entity for me. After working ZK3A on CW and SSB on 40 and 80 meters there was just 160 meters left to be worked.

I did try one time early in the DXpedition when I was awake during a sunrise enhancement. They were very strong for perhaps 10 to 15 minutes. Despite having a good antenna and running a kilowatt I was not successful. Indeed few in this part of North America had success that morning since East Asia, especially Japan, had the better signals.

As the sun climbed above the horizon they faded into the noise. Not being a morning person I tried only once or twice more. Each time they were not on 160 meters. I didn't fret since I was happily busy with other things and the DXpedition was scheduled to last until October 11.

On the 8^th a friend called and told me how he'd worked them early that morning on 160. Rather than wait for sunrise he got up a little past 4 AM (0800Z), a time when it was daylight in Asia and most North Americans are asleep. The sun rises 30 minutes later in JA and the competition rapidly escalates. He planned it well and deserved the contact.

Our conversation motivated me to give it a try. A little after 4 AM the next night I got up and wandered in the shack. I turned on the rig and tuned around. About the only DX was a very weak T30GC making a few contacts with the west coast. There was no sign of ZK3A. In fact they were not spotted on any band.

Before giving up I checked one of the European DX news sites where the first item was that the DXpedition ended early. The boat arrived early for an unrelated medical evacuation so they tore the station down and jumped on board. I had missed my chance for good.

My friend commiserated with my bad luck by suggesting I'd have more opportunities in the future. But for him at his more advanced age, he explained, he might not have another shot at ZK3 on top band so he had to make the effort. It worked for him.

As the cliche goes: you snooze, you lose. Being a DXer isn't always comfortable not even when you have big antennas and power. The DX calls the shots, not you, and you must be flexible if you want to work them. I knew that yet I passed on the opportunity each night in favour of a good night's rest. Until next time.

Aluminum Yagi Construction: Materials and Methods

Be warned: after reading this article you'll probably abandon your home brew HF yagi project and buy a commercial product instead. I am not that sensible. I'll keep building them despite the difficult experience.

With that disclaimer out of way let's dive in. You will learn how I went about the physical construction of 5-element stacked yagis for 15 and 20 meters. The yagis are complete but not tuned. That's my next task. Then I have to raise them and put them to work. I am nowhere near done.

Perils of aluminum shopping

I envy Americans, at least when it comes to aluminum tubing. Despite Canada being among the biggest global producers of aluminum finding what a ham needs is challenging. On the positive side, aluminum tubes, pipes and other shapes are readily available and economical.

Nesting tubes for telescoping tapered elements requires close tolerance of inner and outer diameters. Milling and finishes affect the usability of tubes since the measured and published dimensions may not match or be consistent. The English dimensions used in the United States for tubes and pipes are most common in Canada due to the close trade relationship and despite this being a metric country. When it comes to yagis this fact is helpful. I have heard that telescoping available metric tube sizes can be difficult.

The 0.058" and 0.120" wall diameter high tensile alloy tubes in stepped ⅛" sizes work best for yagis. The former is unavailable here and the latter is uncommon. These tubes are classed as aerospace tubing and though widely available in the US must usually be imported from there. That can be costly since shipping can double the price. Shipping of longer tubes is especially expensive

To keep cost as low as possible I chose a taper schedule after discussions with local suppliers and after considering the tooling requirements to adapt tubes that were close to being suitable for telescoping. All my tubes are 6061-T6 alloy except for the 6063-T832 aerospace tubes I imported from the US. I did my own importing since in every case it was far cheaper than getting it via a local metal supplier.

I received an unwelcome lesson in the difference between mill and other aluminum finishes. More on that later. First I'll describe my taper schedule and construction techniques.

Element taper schedule

The longest half elements are the 20 meter reflector at 219.5" and 15 meter reflector at 143.4". Here are the half-element taper schedules. The centre 1" tube is twice the half-element length.

• 1" OD, 0.120" wall: 60" (20m); 30" (15m)
• ¾" OD, 0.125" wall: 60" (20m); 40" (15m)
• ⅝" OD, 0.058" wall: 36" (20m); 24" (15m)
• ½" OD, 0.065" wall: variable length element tips

All the local tubes were purchased in 20' lengths and cut to 10' lengths for transport in my vehicle. That explains the lengths of the 1" and ¾" tubes. The imported ⅝" tubes were purchased in 6' lengths to optimize shipping and cutting prices. Aerospace tubing comes in 12' lengths.

The approximately ⅛" wall for the inner segments increases the wind and ice survival. For those in the US, it may be more convenient to nest 0.058" tubes in adjacent ⅛" diameters. Ultimate survival was not calculated but interpolated from published designs. These yagis should survive this 135 kph wind zone with capacity to spare, even with modest icing.

The ¾" tube fits snugly in the 0.120" wall 1" tube with no friction at all. I consider this a lucky break since I expected 0.125" to be available yet the 0.120" was available and inexpensive. Since I bought so much they gave me a substantial discount.

The ¾" tubes were machined to fit a ⅝" tube at the outer end so it didn't really matter whether the wall was 0.120" or 0.125". More on that machining below. Fitting the ½" tips into the ⅝" tube with its 0.509" ID should have been easy but wasn't, as I discovered to my dismay.

In tandem with this major project I have also developed a taper schedule for 40 meter yagi elements that utilizes the same taper schedule for the outer halves of the elements. The inner halves will be substantially heftier. I'll leave this construction project for a future article until I've built one of these monsters.

Stepped diameter correction (SDC)

My EZNEC models for the yagis were updated with the final taper schedule for the elements. Using the built in SDC add-on for the NEC2 engine I adjusted the tip lengths to return the yagis to their original designed frequency ranges. This process retains the performance of the designs. For the lucky few with NEC4 although the SDC algorithm is superfluous it is still necessary to adjust the element lengths for the taper schedule.

You must scale the yagi elements since without the SDC for the final taper schedule the performance changes can be substantial. This was most evident when I scaled the 20 meter yagi. Surprisingly the 15 meter yagi, despite having the same taper schedule, required almost no change to the element lengths.

I found it helpful to scale the element in steps, starting with the inner tube section and working outward, checking yagi performance after each step. The changes at each step are not always in the same direction so that a later section change cancels the previous deviation. This is what happened when I scaled the 15 meter elements.

Drilling out thick wall tubes and pipes

The inner diameter of the ¾" tubes is ½". Although the thick wall means I didn't have to nest a ⅝" tube full length inside the outer end must be widened to fit a ⅝" tube. Alternatively a coupler could be used -- " on the outside or " on the inside -- both are troublesome due to needing to import ⅞" tube (0.058" wall) or finding thick wall or solid ½" inserts, respectively.

Reaming out the ¾" tubes to ⅝" must be done precisely. Ideally it is done on a metal lathe in a machine shop. They will do it but it can be costly since I have 40 half-elements to be machined in this manner. So I chose to do it myself.

My first attempt (left) did not go well. I simply put a ⅝" bit in my hand drill, lined it up by eye and had at it. The bit suffered a lot of chatter and even with frequent progress inspections the bit went off centre over the 3" depth of the cut. For my second attempt I first used a 9/16" bit then used the ⅝" bit. The tube wall is thicker, close to the ideal 1/16" since there was less chatter. Doing the cut in two stages help keep the hole almost perfectly centred.

I decided to keep going and do all 40 of them. It took some time. Each tube required at least 10 minutes of work. There were several that drifted off centre and had to be cut off and redone. The 2" to 3" shortening of these tubes has a negligible impact on the SDC. I learned a lot about drill rotation speeds for cutting aluminum and the dos and don'ts of lubricating aluminum. After an initial trial I discarded the lubrication and did the drilling dry, which went faster and with fewer mishaps.

Chuck driven reamers might have done a cleaner job but for the amount of material to be removed. It would have had to be done in more steps and at greater expense since I did not (yet) have any reamers.

I'd hate to do this job again but it did work out pretty well. That is, except for one difficulty which I did not entirely appreciate beforehand.

In the picture you can see the drilling jig and the two drill bits. The technique of screwing together two wood blocks to secure round tubes without crushing or marking them is one I learned a long time ago when I built a bicycle frame from very thin wall chrome-molybdenum steel tubes.

With a standard ¾" bit (not a wood bit) you make a hole as shown. Use a drill press to make it perfectly vertical. The halves are then unscrewed and a sander applied to one or both interior faces to reduce the diameter a tiny amount. Put the halves back together and lightly hold in a vise. Insert the tube and tighten the vise. The tube won't turn except under very high torque.

Pounding a round peg into a round hole

The problem in a nutshell: you can't fit a ⅝" tube into a ⅝" hole. Well you can, but just once since it won't come out after you've pounded it in. This is an example of a press fit and it is totally unsuitable for building yagis.

Even 0.001" makes a difference. My local machinist took one of my ¾" tubes and hand reamed the ⅝" opening to 0.626". The tube now fit though with some friction. After hearing his quote to do all 40 on the lathe I decided to order a reamer online and do it myself. I chose 0.627" to ensure the tubes could be pulled apart in the future.

I use the same ¾" jig to hold the tube. Since I don't have a handheld drill with a suitably large chuck I reamed the tubes manually. I used vice grips and protected the tool with a metal wrap. Unlike a fluted drill bit the reamer is very unlikely to wander off centre. Shaving 0.001" all around is doable by hand without only a little effort.

When the reaming was done the ⅝" tube slipped in easily and hand no discernible slop. Then I did the remaining 39. All this work did save on importing aerospace size tubing, however I might have chose otherwise if I'd thought through the troubles of reaming tubes.

The woes of mill finish

My reaming woes were not over! An unexpected and larger challenge lay ahead. The 200' (60 meters) of ½" tubes I purchases for element tips came with a mill finish just like all the other tubes locally sources. They did not fit into the ⅝" tubes. I was surprised since the 0.058" wall leaves an ID of 0.509", which should leave plenty of room.

Mill versus mirror finish

With a sample in hand I made another trip to the machinist. He put his precision calipers on it and found the diameter to be 0.508". However the diameter is not consistent. That's what you get with a mill finish.

He explained that this oversize diameter is quite common on small aluminum stock. Worse is that for a press fit of similar aluminum alloys a thin layer of material is pushed along the surfaces and can lock the tubes together. That is, once you press it in it won't come out again. I had already discovered this the hard way.

The aerospace tubing, the machinist explained, goes through a grinder that produces surfaces with precise tolerances and a mirror finish that the market demands. The consistent 0.009" gap allows easy nesting to any depth. But I had 200' of tubes I didn't want to waste so I took the reaming challenge.

This was a bigger problem that reaming the ¾" tubes since tips must be adjustable and that requires greater depth of insertion. I first ordered a 0.511" reamer reasoning that an additional 0.002" should be plenty. It wasn't. It was better than a press fit but not enough to allow the tubes to slip together without any binding.

My next step up was a 33/64" drill bit with a shank that would fit the chuck of my handheld drill. Reaming 0.509" to 0.5156" is difficult to do by hand so I chose to do it with power. I did experience binding of the bit inside the ⅝" tube when I rushed the job so I took it in easy steps, being sure to regularly allow the flutes to clear. It wasn't fun but finally it was done and the ½" tubes slipped in to 5" depth. In a pinch the tube can penetrate 7" since I went deeper with the 0.511" reamer.

To add insult to injury, after all the foregoing woe I ordered more of the ½" tubes for other yagi projects. It looked different: the finish was shinier and there was source and material lettering on the tubes, unusual with mill finish. After putting calipers on a sample and comparing with the previous order I grabbed a ⅝" tube and lined up the two. The new ½" tube slipped right through the ⅝" tube just as it should. I'm tempted to run back and pick up more in case they switch suppliers again. No reaming needed for this batch.

Joining tube sections

Apart from the element tips all tube joints are screwed together. This forms a reliable bond and because these joints are fixed there is no need to make them adjustable. Many commercial and home brew yagis use slotted tubes and hose clamps since they are easier to construct.

Each joint -- 1" to ¾" and ¾" to ⅝" -- uses two #8 stainless screws with a flat washer and nyloc. Two holes are drilled through at right angles, one near the edge and near the back of the 3" overlap.

I borrowed a trick from other yagi builders that achieves a superior mechanical and electrical connection. One side is drilled wide so that the screw head rests on the inner tube. When tightened the opposite sides of the tube are firmly pressed together. This is better than relying on screw torque to distort the outer tube so that it presses against the inner tube. With small screws and high tensile strength tubes it may be impossible to adequately distort the tube.

I made drilling guides out of PVC pipe with the hope of achieving enough consistency that tubes could be interchanged and the holes would be aligned. That didn't work out since that close a tolerance was too much trouble and not really necessary. I soon dispensed with them. However the tubes were clearly marked and stored in groups to avoid mismatches.

Because of the tight tolerances of tube diameters (see above) all holes were carefully deburred, inside and outside. All joints, including the screwed ones, were sanded to remove oxide and coated with an aluminum joint compound (I use Noalox, and there are many others on the market) for a good electrical connection and ease of sliding tubes together and, years in the future, sliding them apart.

As mentioned the tips are adjustable by putting two slots in the ⅝" tube and compressing with a stainless hose clamp. I took some care to cut the two slots straight and opposite to each other with two cuts with a hacksaw. The slots were cleaned with a triangular file and a short bevel placed at the bottom of the slot to reduce stress when compressed The twin slots are wide enough that when the hose clamp is tightened the ½" tips are firmly held.

Element to boom clamps

For 15 and 20 meter elements with 1" × 0.120" centre section the clamps don't have to be excessively large. Following the advice in W6NL's Physical Design of Yagis the plates are ¼ × 4" × 6" 6061-T6511. I cut the plates by hacksaw from a long length of the extruded alloy, thus saving cutting fees and getting a sore arm. High tensile strength aluminum isn't easy to cut.

Galvanized muffler clamps secure the plate to the boom. Each size of boom section, ranging from 2" to 3", has its own clamp size and bolt pattern. The galvanized u-bolts for the elements are the same. I could have used stainless hardware at more expense and order lead time, but it is not necessary. Electrical continuity is via aluminum to aluminum contact not through the hardware. Although there is no texture on the muffler clamps the torque from the element is modest even in a turbulent and strong wind so it shouldn't rotate on the boom.

Using the formulas in W6NL's book I calculated the effective diameter of the plate clamps -- 1.673" -- and inserted that into the EZNEC models. The SDC algorithm takes care of the rest. The boom under the clamp electrically shortens the element a small amount -- estimated ~6% of boom diameter by both W6NL and W2PV -- which is pretty well negligible when considered in combination with the effect of tower, guys, other antennas and hardware "bumps".

Gamma match

Originally I planned to use a beta match and acquired the fibreglass tubes needed to mechanically join split driven elements. Instead I am using gamma matches to reduce the mechanical complexity and to gain the gamma's modest ability to attenuate common mode on the coax shield. Beta and gamma matches are about the same amount of work to tune the impedance match and both require similar shortening of the driven element (capacitive reactance).

The prototype 20 meter gamma match is shown mounted on one of the 20 meter yagis. The gamma rod is ½" tube, making it half the diameter of the centre section of the driven element which is a typical (recommended) ratio.

The fixed spacer is PVC pipe mitered to the top 1" tube and secured with a tie wrap. The tie wrap will be replaced with a more durable clamp when the antenna is tuned. The gamma rod fits snugly through a hole in the pipe. The slider for impedance matching is a strip of 1/16" thick mild aluminum alloy.

There is as yet not coax connector or pigtail to terminate the transmission line. For tuning a variable capacitor will be mounted. After tuning it will be replaced with a hardier capacitor of the same value, either a high-Q, high voltage fixed capacitor or (more likely) a length of RG213 (with covering and braid removed) slid into the gamma rod. The latter method is popular since the gamma rod can be slid to adjust the capacitance. However it is not so convenient for initial coarse tuning.

The ends of the slider were manually wrapped around tubes to create the required shape. The wrap is stopped at approximately 330°, the end bent and the bolt holes drilled. When tightened the grip is very good. A conductive grease is recommended on the interior clamping surfaces.

A difficulty was encountered while forming the gamma rod end. I could put the bend in the right place at the beginning of the process but found it difficult to prevent the long straight section from creeping along the form during the last half of the forming. As a result a couple of the shorting straps are ¼" short. After recalculating the gamma match with the reduced values my concern was assuaged. The gamma capacitance value barely changed and the short position goes outboard no further than another inch.

Booms

The four booms were constructed from a mix of pipe and tube. I tried to find a balance between weight, wind load and cost. Most of my pipe is surplus and inexpensive. When I can't get what I want I either modify the boom design to use what I have or I buy new material as needed. Large tubes and pipes are readily available new and are not too expensive.

The side mount yagis use the largest diameter tubes. Their relatively thin wall makes them unsuitable for rotation at great height. These were built last year and stored until I was ready for them.

The rotatable yagi booms are heavier, narrower and have a modest wind area. They are a mix of surplus pipe and new tubes. The 20 meter rotatable boom is the heaviest with a centre section that is 2-½" schedule 40 pipe (2.875" OD). I made liberal use of my relative strength spreadsheet to contrast and compare alternatives.

Some choices were made based on good fit between various sized tubes and pipes. In one case I had couplers machined but those didn't work out and have been put aside for a future project. I am not bothering to describe details of the booms since my choices are unique to my circumstances.

Waste

Machining, drilling and cutting the elements, booms and clamps produces a lot of aluminum waste. Constant cleaning of the tools and work surfaces was necessary to avoid mishaps.

No matter how well I cleaned up each day aluminum shards appeared everywhere throughout the workshop, on my clothes and hair and in the house. The latter occurred despite cleaning of clothes and boots. The stuff is insidious.

Regrettably there isn't enough metal weight to make recycling worthwhile. However it does occupy a large volume since the shards, especially the strings and spirals spun off drill bit, pack loosely. It'll all be thrown out.

Of greater concern is steel waste since it is darker and therefore more difficult to see. That matters since it is far more likely to cause cuts and slivers than the softer aluminum. Fortunately there is less steel waste, the bulk of it from fabricating the rotation and support system for the mast and yagis.

Putting it all together

Here we have the first of the assembled yagis: the side mount yagis for 15 (left) and 20 meters. The gamma matches are not yet ready. That and initial tuning is coming up. It isn't a trivial task since the feed points are far out on the boom. Access to the feed point is required for every tweak to the gamma match. More on this later.

Element positions were previously marked on the boom. I attached the element clamps then the elements, tightened everything and sighted along the boom to align the elements. To do this properly the boom must be lifted above the ground. That will be enough height to clear the fragile gamma match. I use old cable reels for supports, in this case from 500' spools of EHS guy strand.

Was it worth it?

That's a very good question. For myself the answer is yes despite all the difficulties. It was a superb learning experience and, aside from the time invested, economical in comparison to commercial products. There is also a sense of accomplishment overcoming the challenges of design and fabrication.

Of course the project is not complete. After the tuning the yagis must be raised and fed for stacking. The switching system for choosing lower, upper and both for the 15 meter and 20 meter stacks will be a commercial product. Little money will be saved building my own and it will look and work better. There is no shame in buying some products even for a devout home brewer.

As I finish this article friends are scheduled to come over to assist me with tuning the yagis. Three are built and the fourth (20 meters) is awaiting completion of the boom. I'll have more to say once the next stage is completed. For the present I am relieved to have all this aluminum out of my garage workshop so that I can move around and access things that have been out of reach for weeks.

Cutting Pipe Square

I cut a lot of pipes and tubes building towers and antennas. Most of the time I do rough cuts with a hacksaw or cutoff saw since the angle of the cut is not critical. It may look ugly but once it's up in the air no one will know.

For small diameter thin wall tubes I use a pipe cutter which is quick and makes a square cut. Except that a pipe cutter does not cut cleanly since rather than removing material it pushes it to either side forming a ridge, inside and outside, and the cut itself has a bevel. These must be filed off. The squareness of the cut can be distorted if the file is not kept level.

A hacksaw cuts more cleanly. However to make the cut square it requires a miter stand or the tracing of a reference line when cut free hand. Better is to use a metal band saw. Since my cutting needs are modest I have not invested in a band saw for my workshop. Instead I use a variety of manual cutting methods.

For large diameter pipe, steel or aluminum, the challenge of cutting the pipe square is multiplied. Manual pipe cutters of such a large size are rare and expensive. Even if available they require a lot of muscle. A hacksaw can be used if a square cut can be traced beforehand on the surface.

This is not difficult if the pipe has a known square end to use as a reference. Surplus pipe often does not have even one square face. A different technique is therefore required. I did this recently when I required a square cut on a 3.5" diameter aluminum pipe. I took a few pictures to show how it's done.

Draw a circumference

It's quite easy to scribe a circle around a pipe. You start at point A, travel orthogonal to the axis and come back to point A. But without a guide the line will almost invariably be a ellipse and not a circle. That is, it won't be square and the cut will be at an angle.

We need a straight edge that wraps around the pipe and does not crinkle, warp or that can lie askew. Guides I've tried and rejected include: tape, hose clamps, another bigger pipe, steel and fabric tape measures and drawing a line with a fixed marker while the pipe rotates. They fail because they are not rigid, rigid but not when stressed, a better but less than accurate edge or mechanical instability while drawing.

After considering the problem I found what is perhaps the most unlikely solution and one that covers half the space of my office desk: paper. Although it is easy to crumple and warp it is also easy to have it sit flat when wrapped around the pipe with a bit of tape and care taken to avoid "bubbles". The paper edges are a great straight edge when supported on a rigid surface such as a pipe. Paper is flexible with dimensional rigidity and is superior to straight wraps such as hose clamps because the sheet is wide: if it has a warp it will be immediately visible and can be corrected.

The pipe in the picture is 3.5" OD so an 11" paper edge (standard North American sheet height) almost exactly makes a circumference -- 3.5 × π = 10.9956. In this case the sheet is a little short since it doesn't quite reach around the pipe.

Masking tape on the pipe makes it easy to trace a fine line. The line doesn't have to be perfect provided there are no paper tears. If the pen or pencil wanders just fill in the gap and continue.

Making the cut

Starting the cut is the most crucial step.

Lie the pipe flat on a stand where it can't roll but can be easily turned by hand. I use an ancient Workmate (40 years old!).

With your gloved hand (for protection) precisely guide the blade along the drawn line. Cut with light pressure, taking care to keep the blade from wandering. Correct any deviation immediately.

Rotate the pipe a bit and continue. When you've gone around once you have a shallow cut that will help keep the blade on the line. The tape will tear or be marked if the blade jumps as you cut, warning you to correct the mistake. This is most likely while the cut is shallow.

Continue cutting while rotating the pipe a little every few seconds. As the cut goes deeper you can use two hands on the hacksaw if the stand opening is wide enough that the blade's force doesn't rock the pipe.

As you go deeper take care to align the blade so that it doesn't lean to one side. Many hacksaws, such as the one shown, seat the blade at a small angle for improved work visibility and to counter a natural inclination to lean the hacksaw towards the dominant hand. A straight cut means less filing to remove a bevel and less chance of warping the pipe edge from excessive filing.

Eventually the blade will penetrate the wall of the pipe. Avoid the temptation to speed up and not rotate the pipe. Keep rotating the pipe and the cut will be cleaner.

Finishing

After completing the cut there is some filing to be done. Use a flat file across the full diameter of the pipe rather than filing one wall. This will keep the file flat and maintain the levelness of the surface. Burrs on the outside can be removed with the flat file and a half round file used on the inside.

The finished pipe stands perfectly vertical when on a level surface. When fit to the finished work the squareness of the cut was confirmed.

The use of this cut pipe will be described in a future article after I complete the new 140' tower. It forms part of the rotation system for the top mast. All the mechanical work to the top two sections is being done on the ground before being hoisted up.

One Step Forward

My one step back a few weeks ago continued to the point where I had just one HF antenna: the 80 meter vertical. This kept me off the air and focussed on rebuilding. The removal of almost every antenna was necessary to move and repair antennas in preparation for the next configuration of my antenna farm. It has been a very busy time.

With the help of friends I am again active on all bands from 80 through 10 meters. Until more antennas go up my flexibility is limited, so I cannot call this progress. That explains the title of the article. Over the next month there should be enough progress that I can truly claim that I have taken one step back and then two step forward.

For now it's just one step forward in which the station is different but at similar capability to what it was a month ago. In this article I'll run through the progress so far.

TH7: high tri-band yagi

I will have little to show for 10 meter antennas when this year's work is done. That is acceptable for the next year since signs of life on that band will remain elusive for at least that long. With a large tri-bander up at 43 meters this will give me flexibility during contests to target, say, South America at the same time as Asia on 20 meters. I am assuming my new 20 meter and 15 meter stacks on the new tower will be ready and I am working hard to make it so.

I really like this picture. The Hy-Gain TH7 dangles at the bottom of the tram line fully rigged and ready to be hauled over the hay field to the top of the big tower. Posing with the antenna is my trusty ground crew (left to right) John VE3NJ, Don VE3DQN and new ham Alan VE3KAE.

Notice how the antenna is well balanced so that the boom is level and the elements point straight ahead. This is the correct orientation to clear the guys and not strike the tower or mast. Those element tips are fragile. Two people lifted the boom as the tram line was pulled tight to prevent the elements from catching on the ground. Two people manually operated the haul rope during the lift. Power makes the job easier but increases risk of damage when the the antenna strikes an obstacle.

Many hams attach yagis to tram lines with custom made rigs that guarantee good orientation. I do it old style with ropes. With practice ropes work very well and allow for rapid removal and easy packing at the top of the tower, an important consideration. In this instance it worked beautifully as the close spaced driven elements of the TH7 slid right around the tower and mast.

One mistake I made was to point the antenna backwards. Although this is easy to correct by calibrating the prop pitch rotator controller the direction I dressed the cables and rotation loops is not compatible with a north centred rotation, which is the preferred method in this part of the world. I avoided rotation until it was fixed a few days later.

The TH7 was retuned to resonate lower in the band. SWR is a little higher than ideal at the low ends of 15 and 10 meter. but better than it was before. The boom is attached to the 3" mast using the same modification I used for the TH6. I shortened the DX Engineering saddle clamp on the top side to avoid it contacting the phasing line between the driven elements.

Other tri-band yagis

The reason the TH7 is up there and not the TH6 is because the close spacing of the driven elements does not easily permit tower side mounting. The TH6 is better for this. It was trammed to 75' and pointed roughly south to permit working Caribbean and Central American multipliers and the southern US, all of which are present during opening to Europe on the high bands. It uses the same side mount bracket as used previously for the Explorer 14.

The Explorer 14 is now gone to its new home where it will soon bring home the DX to its new owner. Although a small antenna it did well for me during the past several years.

The TH6 was inspected after removal from the tower. A couple of defects were discovered which I assume these were responsible for problems that began last winter. The worst was the poor design of the driven element clamps that connect wires to the balun and beta match line.

The tabs on the aluminum wraparound clamp bend when the bolt is tightened. There is no provision in the TH6 to prevent this so the wire studs don't sit flush against the tabs: they wobble. My antenna was particularly bad due to its great age.

I added two backing nuts to allow fine adjustment of the clamp pressure and squarely bond stud and tab. The TH7 is better than the TH6 in that it has one backing nut, but still not the two I used. The studs were weatherproofed after taking the picture since the tinning has deteriorated. The hardware is stainless.

I took the opportunity to move the yagi's optimum performance higher on each band. Previously it was set for CW so the SWR was poor at the upper ends of the SSB band segments. Not wanting to lose CW performance I opted to shift it slightly higher, just below the settings for "Lo Phone". Because there is only so much bandwidth possible with a tri-band trap yagi some compromise is necessary. Eventually the TH7 will be converted to a TH6 so the two can be stacked for added performance. The conversion is necessary to achieve a similar impedance and therefore good power division.

I made a mistake with the tram which at least doubled the time to raise it to its new home. The upper tram anchor and haul rope pulley were too close to the mounting position. Manoeuvering a big yagi in a stiff breeze with ropes getting in the way and pulling the antenna out of my hands was too much. We lowered the antenna and redid it properly. Expedience costs rather than saves time.

XM240 40 meter yagi

This small 40 meter 2-element yagi has been returned to its original location on top of the Trylon tower at a height of 21 meters. The lift went pretty well considering the necessity of dropping several above grade cable runs and navigating the long elements around the trees that have grown over the previous two summers.

A few modifications were made to improve the antenna. The previous owner modified the antenna to make it more robust in extreme weather. He did a fine job of it but he should have chosen better hardware when he replaced the Cushcraft element-to-boom clamps. The cheap galvanized muffler clamps do not have enough grip to prevent the elements from rotating.

I inserted galvanized mesh under the clamps to provide mechanical texture to improves the grip. While not ideal I could not simply use better clamps such as the flattened and textured DX Engineering Cycle 24 clamp since there is no reliable sizing of muffler clamps and I'd have to drill more holes in the aluminum channel. Too many holes risks weakening it. Time will tell how this improvisation deals with the wind.

The other improvement was to ground the reflector element to the boom. This is a popular mod to reduce precipitation static by providing a path to ground for the static charge. Performance is not affected. Precipitation static was a serious problem at 150'. We've had one rainfall since the antenna went back up and...there was precipitation static, though not as bad as in the past. I'll continue to monitor.

I adjusted the rigging to ease attachment to the mast. Ideally two on the tower eases installation of this unwieldy yagi but I made do on my own by adjust the rigging and the procedure. The lift was done the same day as the TH7 with the same ground crew. I spent two days beforehand to prepare the antennas and rigging on both towers to best utilize the time of my friends.

In the picture I am in the process of attaching the mast clamps. There are a few interesting features of the rigging that are worth mentioning:

• I attached the boom truss to the lift rope. This kept it out of the way during the lift, made it easy to slip onto the mast and by keeping it in one piece there is no risk of one end slipping out of reach while it is being assembled on the tower.
• Long ropes are looped over each side of the boom. These tag lines allow fine control of antenna orientation in tight spaces. When done pull one end of the rope and it falls to the ground.
• Precise positioning of the mast clamp needed to insert the clamps for an antenna this size is no easy task for one person. I used a couple of cargo straps as a third hand. I previously slipped all 4 clamps onto the mast and raised them one by one, top to bottom, for attachment. The rigging must keep the plate flush to the mast since there is nothing on the boom to grab onto to rotate it.

There are a few reasons for placing the XM240 at this new location. First, I need a directional yagi at intermediate height for contest work. Although side mounting it on the big tower is possible I do not have time this year to build a side mount suitable for almost full 360° rotation. Second, the Trylon is close to the house and there are many weak noise sources that are audible on 20 meters and above where the atmospheric noise level is low. This is not a problem on 40 meters. For long paths I have another plan for this autumn: a full size rotatable dipole above the TH7 on the big tower.

80 meter inverted vee

The 40/80 meter inverted vee that was on the Trylon is headed to its new (old) home on the 150' tower. However the 40 meter element of the fan dipole has been removed so that it's solely for 80 meters. It is no longer needed on 40 meters and it used to twist and tangle in the wind which would make it unusable on 40.

The tower mount has been improved from an ABS pipe to a steel angle bracket. The new bracket is far stronger and will take more tension. It is also a better mount for the balun (common mode choke). Strain relief for the wire legs keep stress away from the balun studs.

Modelling tells me the best pattern for short paths and low directivity is at a height at or a little above 30 meters. This will  also keep it well away from the other antennas on the tower. Unlike its original installation the two legs will go down into the tree line on the north end of the hay field, avoid ground anchors in the hay field. The model shows almost no effect on the pattern by doing this.

It should be a good antenna for the QSO rich northeast, mid-west and south-central US. After sunrise and before sunset a horizontal antenna often works better than a vertical on 80 meters on both short and DX paths. Unfortunately it's resonant frequency is ~3700 kHz, ideal for neither CW nor SSB. If widening the legs of the vee more doesn't help I'll lengthen it to lower the SWR below 2 within the range of 3500 to 3600 kHz. My primary use for the antenna is CW contests and DXing.

One step forward

Other antennas

With the bulk of the tramming on the 150' tower is done I deployed the radials for the 160 meter antenna and connected the over-ground coax. I kept the field free of trip hazards for the safety of the crew. The match is different each year I deploy this antenna. This year it resonated at 1800 kHz so I adjusted it to resonate at 1825 kHz. I believe the variability is due to the distance from the antenna from guy wires and the directions the radials run, neither of which are identical each year.

Work on the 80 meter vertical yagi is delayed. Since this antenna can be done by myself on the ground in the cold weather it is low priority. It's just a little frustrating that this project is taking two years to reach fruition. However I budget the time and energy I devote to amateur radio so that it doesn't become a burden. On the positive side it really is almost complete.

The last stage of aluminum work on the 20 and 15 meter long boom yagis is done. I have only to cut and insert the element tips, mount them on the boom, build gamma matches and raise them for tuning. October will be a busy month.

The mast bearing plates for the new 140' tower were assembled and declared unfit for use. I made an error in the template that requires modification in my workshop. This is a temporary obstacle. I expect to raise the top sections of the tower along with the mast and prop pitch motor by mid October.

When everything is completed I will be ready for the winter contest and DX season. Next year will be less busy with only a few large projects. More on those in the coming months. Right now I remain focussed on antenna building and becoming reacquainted with the HF bands since I did little over the summer other than 6 meter DXing.