Sunday, April 30, 2017

Gift Basket

When you do regular business with a company a bond of mutual trust often develops. We do a lot of buying from fellow hams, retail outlets catering to our hobby and other companies that have the hardware and services we need to build and maintain our stations.

A good vendor will be more responsive to your needs when you offer them returning business and you can rest easy knowing that you are getting good value for your money. Occasionally the vendor will go the extra distance to show their appreciation for your business. On your part you need to be a good customer by being reasonable with your expectations and, yes, settling your account promptly.

The local tower service company doing the foundation work for my big tower surprised me recently with a box of hardware. This is scrap from commercial towers and antenna installations. Since for safety and engineering reasons it is common nowadays that new material must be used in building projects used but still good material often ends up as scrap metal or goes to the landfill.

The quality of most of the hardware is first rate: hardened steel (grade 5) and well galvanized for durability in a harsh environment. Fasteners are almost all ⅜" and ½" sizes, which I often need. I took the picture after sorting.

Some of the hardware is lesser quality and some that was discarded due to damage. You can usually spot the lower grade steel hardware by the evidence of bends, tears and dimples from use. Shiny hardware is typically plated rather than hot dip galvanized. You can see examples of both in the group of nuts at the bottom centre of the photo.

Those large size u-bolts (4-½" opening) are especially valuable for one large antenna project I am currently considering: a full size 40 meter yagi. The smaller u-bolts will most likely be used as element clamps on HF yagis.

If you investigate the pricing for hardware of this size and quality you'll find that the total adds up quickly. Any hardware I don't need can always be re-gifted to other hams.

The gesture from the company is appreciated. If I have to spend money I prefer to spend it with people who treat me well. It's worth searching them out and to treat them well in return.


Since we cannot count on gifts it helps to be a good scrounger. I'm sure you've met hams like this, or perhaps you are one. They have an instinct for reaching out to people and businesses that might have surplus material and products that can be turned to good use by an ingenious ham.

A scrounger needs to be outgoing. You have to cold call people and build personal relationships. Scroungers (like the best sales professionals I've worked with) are very protective of the relationships they build so you cannot often ride their coattails. Scrounging is something you must learn do yourself.

Quite a few big guns built their stations scrounging coax, towers, hardware, electronic parts and much more, saving countless thousands of dollars along the way. They are to be commended. I am not as good at scrounging as I'd like to be so the occasional gift basket is very welcome.

Friday, April 21, 2017

Asymmetric Copy in Contests

It stands to reason that except in superb conditions that one side of the QSO copies better than the other. Indeed it would be remarkable if copy was equally good (or bad) since each station has a unique set of antennas, noise, QRM and propagation. This can make for some curious exchanges during contests.

Even when SNR (signal to noise ratio) is high there can be asymmetries in copying. On SSB this may be due to language and accent for the majority of hams who are not using their native languages, or simply by poor enunciation by those who fail to realize that a communication channel with limited band width and dynamic range makes copy more challenging than talking in person. There is also the all too common practice of poorly adjusted audio. On CW it may be poor sending, deviations from standard code element length and spacing, or sending faster than the other ham can comfortably copy.

Putting those situations aside I want to focus on QSOs between operators who are doing their utmost to get the message across: in this case call signs and contest exchanges. I'll focus on CW and SSB since I don't have sufficient experience to discuss digital modes.

Run versus S & P

Let's imagine we are tuning across the band and run across two adjacent signals, one strong and one weak. Which one do you tune in first? Even if you are disciplined enough to focus on the weak one I bet that you are still strongly drawn to the strong one. This is perfectly natural since it is less work to copy the stronger station well. Struggling with a weak signal costs time and time costs points. We are more inclined to do the hard work late in a contest when all the strong ones are already in the log.

However, it is not quite so straightforward. When you tune in a strong signal in the clear you will most likely copy the call sign the first time it is sent. You will most likely easily copy the exchange. The same is often not the case on the other side of the QSO. You may be running less power and a smaller antenna; they may be experiencing strong QRM from other callers and adjacent signals near to you that you don't hear because they are in the skip zone or off the side of the beam.

It should therefore be no surprise that for stations you copy perfectly while you S & P that less than 100% of them will copy you as well. Some of the time or much of the time, depending on many variables, they will ask for repeats or you'll have to correct their copying error. During the two years my contesting was exclusively QRP the percentage of running stations that could copy my call sign and exchange the first time was not high. On the low bands it was often no better than 25%.

Now let's return to the weak station you earlier skipped over. More S & P operators than you might imagine won't pay any attention to the ones that are hard to copy. I'll assume you're not one of those, since as a contester you should never overlook potential points (and multipliers).

So you listen and listen, perhaps taking a little time to completely copy the call sign and perhaps you'll also note the exchange being sent. For many it is only at that point you make your call.

Consider what's going on here. You spent time to copy the full call and ensure it is not a dupe. You have already had one or two opportunities to copy the exchange. Even if it's a serial number you know what number comes next and you'll be ready for it!

The running station has not had that opportunity. Their probability of correct copy on the first try is perhaps, on average, no better than yours. Yet you've already gotten past that obstacle. Now it's their turn. The weak running station is even less likely to copy your call and exchange on the first try.

The lesson here is that when you S & P you should not be surprised that the running station will need repeats of your information. For the running station many callers will not be readily copied and you'll have to spend time to correctly solicit their information.

Example: Ontario QSO Party

As an experiment I did 100% running in the recent Ontario QSO Party. That is, sitting on a frequency calling CQ and never hunting other stations. The contest has light activity and I wasn't concerned about my score, only giving out QSOs to others. This is not a bad way to make it easy for non-VE3 participants to find me, and my perhaps uncommon county multiplier. Many of the active VE3 stations spent much of their time running as well, perhaps for the same reason.

The objective of my experiment was to see just how often the callers were difficult to copy. Well, it was surprisingly often. While a sample of n=1 is not statistically significant my results do fit well with my thesis and my recollection of past years of contest experience at larger stations.

My springtime QRN levels on the low bands was quite high during the contest, with several electrically active rainstorms passing through or nearby. That could have contributed to asymmetrical listening ability. Asymmetrical power wasn't a problem since I kept to the low power limit of 150 watts, which is on par or less than the majority of callers.

On 80 meters I found I had to use the Beverage all the time even though it favours Europe and almost all callers were off the side or back of the Beverage. The SNR was almost always better than the inverted vee. This worked less well on 40 meters, partly due to the Beverage's sharper pattern on that band. The 2-element yagi's directivity is not very good, which is typical of this type of antenna.

There were many callers I could not copy at all, while with other I would only catch a letter or two of the call. It seemed surprising they were copying me. Perhaps they had lower atmospheric QRN, more directive antennas or there was power asymmetry.

One obvious problem was looking west on 40 meters soon after my sunset. At that time the other station's band noise will be lower than mine. This is typical of the low bands. As soon as propagation is enhanced by the arrival of darkness the noise level rises along with the signals from the dark hemisphere.

Stations west of the terminator hear me fine while I struggle with the atmospheric QRN accompanying that of signals from the east and south. This is the same phenomenon responsible for the difficulty of working clearly heard Europeans before sunset on this side of the Atlantic Ocean.

In many cases I could not come up with a good explanation of why copy would be difficult. QRN would be low and QRM absent. Obviously I can't know what is going on at the other side of the QSO. Maybe they were driven there by a spot (or skimmer) or maybe they had already spent some time copying me before calling. All I can know for sure is that copying asymmetry was common.


Let's face it, for the upwardly mobile contester it is necessary to run a lot to improve scores. That guarantees you'll be struggling with many callers that are difficult to copy. Since you must do it there are things you can do to be best prepared to deal with it to your (and their) benefit. Scores will improve and frustration levels will decline as abandonned QSOs are reduced in number.
  • Directive antennas: One sure way to improve copy on the low bands, and even on the higher bands, is with highly directive receive antennas. This can be as simple as a small loop, or can be a Beverage or phased vertical array. Transmit antennas are typically not highly directive on 80 and 160 meters so a more directive receive antenna is a good addition. The results can be surprisingly profitable. Since directive antennas are directive you'll need more than one, or at least an antenna with 2 or more selectable directions.
  • F/B: Antennas for all bands should have strong suppression off the back and sides, preferably with minor lobes that are no more than -15 db than the main lobe, and preferably much better. On the low bands phased vertical arrays are often the best at this, while on the high bands a Moxon rectangle or similar critically-coupled 2-element yagi, or optimized yagi with 3 or more elements.
  • Hunt down noise sources: Any noise source -- power line, Ethernet, USB, appliance, electric fence, etc. -- is a potential killer of QSOs, especially on an otherwise quiet band. Do everything you can to locate and silence noise. If you can you should place your antennas as far away from buildings and power lines as possible, or where productive directions for QSOs are over quiet zones.
  • Filters: Learn how to alter your filter settings quickly so that you waste little time asking for repeats. This include bandwidth, centre frequency, noise reduction, notch, and RIT. The last is important since you are less likely to hear a weak caller unless you tune above and below your frequency. You don't want to overlook them just because they failed to zero beat properly.
  • Partial call database: This one can be controversial. Many contest loggers will search for calls that are similar to the partial or full calls that you type in. This can help you to deduce that the caller is one of those, either a known contester or a call you've worked before in this or a previous contest. The technology exists and it's your choice whether to us it. Whatever you do, confirm the call with the caller. Never assume.
Effective running requires good listening habits and supporting technology.

Monday, April 17, 2017

Bracketed Tower (again)

I purchased a 29' (9 meter) light duty television tower 4 years ago soon after I returned to the hobby. After starting off using house eaves trough for an antenna I wanted something better since it seemed I wasn't going to wander away from amateur radio for another 20 years.

At first the tower was deployed as a guyed tower supporting a multi-band dipole and a 40 meter delta loop. When I replaced that with a stronger tower suitable for a rotatable yagi I bracketed the small tower to the house, installed a tall mast onto it and used that to support a fan dipole.

A small tower such as this is not part of my current more ambitious antenna farm planning. Even so the tower is up once again. Again it is bracketed to the house. Its intended use is LTE terrestrial wireless internet access. My current obsolete wireless service was a special order so that I could get connected quickly when I moved in last fall. The ISP wants to move me to the new, faster service and I am eager to oblige.

So while not a tower for amateur radio purposes I thought it might be of interest to any readers who want to press one of these inexpensive light duty towers into use to see how I did it. Bracketing a tower to a building, while convenient, must be properly done to avoid compromising the tower, personal safety and the structure of the building.


This particular tower -- Golden Nugget -- is very common in Canada. Other countries have similar products on the market. This tower has three 10' sections (top section is 9' 6") made from 1" OD 18 gauge tubular steel pipes and horizontal cross members of formed sheet metal. The welds are a bronze-gold colour, hence the name. Load capacity is modest, perhaps 2 ft² when bracketed no more than 10' (3 meters) below the top.

A flat plate with flanges is designed for ground mounting the tower. The flanges bolt to the bottom section and holes in the plate are meant for driving stakes into the soil. I prefer a more engineered base so I fashioned one out of 4x4 preserved wood. I kept the one I had previously built.

I just had a garage built next to the house, which was my cue to begin the grading/drainage work between the buildings, including setting the new grade and then the base for this tower. Until now I wasn't quite sure at what level to set the base.

Choosing the location

Without considering other factors the ideal location for a bracketed tower is where the bracket can be placed at the maximum height. On a typical bungalow this would centred on one the side of the house with the bracket nestled near the roof ridge. There are more options on a two-story house since many points allow bracketing quite high.

Of course there are other factors. One is aesthetics and another is safety. My previous house allowed for several options with some being unsightly and others not allowing good placement of antennas (e.g. near the property edge). On my current dwelling there is really only one good place for the tower even though it is not the best for bracket height. All the higher options are in front of large windows or in the middle of a deck or balcony.

However my chosen location is not bad, allowing the bracket to be just under 16' (5 meters) above grade, which is more than halfway up. Since the only antenna will be a compact dish I do not have to worry about where HF wire antennas would go. This is good since the roof of the house is steel, which is less than ideal for HF purposes.

Selecting the anchor points

To be effective the brackets must tie into the frame of the house. On a typical North American wood frame house this is usually not a problem, if one is careful. Unfortunately from the outside it is not always clear where the studs, headers and trusses are located.

Being a country house with a deliberately rustic design the exterior is clad with batten board and striping. There are no indications on close inspection of where the frame members are located. However I do know that the frame is sheathed with chip board, on top of which are wood straps to which the cladding is nailed. None of those is acceptable for a tower bracket since they offer little resistance to tension.

The fascia is no better. Typical attachment of wood fascia is nailing into the ends of rafters or, in this case, short studs that bridge the distance from the outermost truss to provide an overhang. Again, those nails offer little tensile strength. Worse, the fascia and soffit block access to the top of the truss, which would be a good anchor for the bracket.

Peeking through the screened attic vent told me little. Other than a lumber frame around the vent (not a good choice for bracketing!) I could see little. The house blueprints only provided generalities not specifics of how the wall was constructed. Density meters for locating studs, pipes and wires are inadequate to locate framing from the exterior.

When my previous house was built I took lots of pictures (film, remember that?) of the house framing before the insulation and drywall were installed so I knew where everything was located. I only needed to take some measurements, compare to the pictures and I could find suitable anchor points to within an inch. But for this house I needed to see inside.

Before purchasing the house neither I nor the inspector I hired could find an access to the attic over the bedroom wing; the rest of the house is post and beam with a cathedral ceiling so there is no attic except here. I puzzled this one through, periodically looking up as a walked around the house. That's when I spotted someone odd about the overhang in front of the house. I had one of those "aha!" moments.

Minutes later with a ladder and a few tools I was in. I took pictures of what I could see of the wall I'd selected. Coincidentally we are looking directly across the roof of the shack. I did not enter the attic since quite a lot of care is needed to cross the rafters in a modern house with engineered trusses and heavy insulation that buries all the structural bits. I've done it when necessary, and I can assure you it isn't much fun. It is very easy to damage the ceiling, and yourself.

However all I needed was the picture. All that needed to do the rest is one measurement from the outside to calibrate the scale of the picture. For me that was the width of the vent frame: 24". From that I could determine the location and size of all the dimension lumber and how it all ties together.

I chose the 2x6 header over the vent frame for the bracket anchor. It provides a wide solid support for long lag bolts and it is suitable tied into the end truss. The sheathing, though weak on its own, adds to the lumber connections so that tower loads are distributed over the framing. For a larger tower with an HF yagi I would not recommend this choice. For my internet dish or for wire HF antennas or a small VHF yagi this anchor is perfect.

If you are going to go big with a bracketed tower I suggest you either hire an engineer or find a more secure anchor in the frame. On my previous house I was able to anchor into two layers of 2x6 header sandwiched between the rafter of the trusses and the exterior 2x6 support walls. That will take substantially more load than what I have selected here.

Installing the brackets

I kept all the hardware used to bracket the tower to my previous house. Some is custom and some is specifically made for bracketing a small tower. In the picture below is pretty much all that I needed, other than the hardware store perforated angle steel I use to make the bracket arms and the U-bolts to attach the arms to the tower legs.

The L-brackets are attached with lag bolts to the house (upper flange) and with grade 5 bolts to the arms (lower flange). I picked the two in the best condition. These L-brackets are sufficient high grade to resist bending under load or under bolt torque. I chose to use 5/16" lag bolts rather than anything larger since the tower load is small. The shorter bolts secure the base plate to my homemade preserved wood base.

With a little geometry I calculated the required distance between the L-brackets to that when positioned the tower faces would align with them. As it turns out I made an error during measurement and they were 1" off. Thus one of the bracket arms wasn't flat against the tower face. This is not a serious problem so I didn't bother moving the L-brackets, and avoided repairing unwanted holes in the siding.

Raising the tower

Several hours during a warm spring day was all it took to attach all the hardware and raise the tower. It helps to have a friend although I did this job on my own.

The L-brackets went into the header just as planned. In one case when drilling the bolt holes there was the expected gap between exterior board and sheathing, while in the other I got lucky and hit the wood strapping between those layers. In the latter case this permitted me to torque the lag bolts without undue concern. The other required me to not tighten the bolts too much since that would only bend and possibly break the exterior cladding board.

It is important that the holes through the intermediate layers permit the lag bolts to slip through; the threads should not bite into the siding or sheathing. Collars are available for lag bolts to allow the bolt to take full torque without bending the cladding. This requires carefully drilling a hole for the collar or it will sit too deep or too high and not do the intended job. I didn't bother with collars, even though I have them in my stock of parts.

The full length hole is smaller so that the lag bolt threads engage the frame lumber. Although you skip this hole, drilling a hole reduces the chance of splitting the wood and thus compromising the strength of the bracket. For my 5/16" lag bolts I used a 3/16" drill bit.

With the L-brackets installed I sat the bottom tower section on the wood platform and weighed it down with stones (I have plenty on my property!). From the ladder I lifted the next section and dropped it in place. Bungie cords, one per L-bracket temporarily hold the 20' of tower upright.

The small sledgehammer and scrap wood you can see were needed to press the section into place since the legs were slightly ovalized. They are easily deformed when tightening the splice bolts. Separating sections can be difficult if the installer was over-enthusiastic with the wrench.

The next step was to attach the bracket arms to the L-bracket and tower legs. If you don't have the manufacturer's bracket arms you can fashion your own, as I did, from galvanized or painted steel of suitable strength. If this makes you uncomfortable I strongly recommend you only use the purpose-designed brackets from the tower manufacturer. The previous owner of this tower fabricated his own bracket arms. Although they were very poor strength the tower survived for years. I rejected them.

With the brackets holding the tower the bungies were removed and the tower made vertical with a long level. Only then is the base plate bolted to the wood base.

To lift the top section I opted to reassemble my old light duty gin pole that I had built for raising DMX tower sections. The brackets I made fit the Golden Nugget reasonably well but require securing the gin pole to the tower since with horizontal cross member the gin pole can easily slide.

Although the tower sections are light I strongly recommend a gin pole since it is harder than you might guess to lift a 10' section above you, holding it perfectly vertical, aligning all 3 legs at the same time and pushing it down into place. I know some rare individuals with the physical gifts to do it, however I am not one of them and it is  almost certain that neither are you.

The mast is easy enough to raise and slip into place without a gin pole, if you are careful to keep it nicely vertical during the procedure. Surprisingly little deviation is enough for gravity to twist it out of your grip and cause injury to you and your house. Don't hesitate to ask for help if you need it.

All done

As the sun set the tower was complete and the tools and materials put away. Now I have only to inform my friendly neighbourhood ISP to visit at their convenience to install their equipment and upgrade my wireless internet service.

Monday, April 10, 2017

Swimming Hole

We've had a lot of rain over the last week. So much that roads are flooded and some homes are threatened throughout eastern Ontario. Couple that with spring temperatures and runoff due to incompletely thawed ground and you get something like this:

Sad, isn't it? However it is not as bad as it looks. Soon enough the water level will drop and the rest will be pumped out. Then the debris in the hole will be removed. The concrete work on two holes was completed in the fall which leaves two swimming holes (this one and one more) yet to be converted into tower foundations.

Soon enough that anchor you see will hold 2,000 kg of tension, its share of holding up a big beautiful tower. For now I thought some readers might enjoy this view of my impromptu swimming hole. The full story of planting this tower will come when I've got it done. With a little bit of luck that should happen by early May.

Friday, April 7, 2017


Many years ago I bought and absorbed The Complete DX'er by W9KNI. If there one overriding lesson from that book was the importance of listening. Of course there was no global DX spotting network -- just pockets of friends who would let each other know when a rare one appeared on the band -- making listening, and lots of it, an absolute must for the DX enthusiast.

Although I had been around long enough by then to not learn much from the book it put what I was already doing into perspective , therefore enabling me to better understand the strategy of good listening. When I returned to air a few years ago after a long hiatus from ham radio I soon learned that too much listening could actually be detrimental. While I listened someone else spotted the rare one and those receiving alerts from the spotting networks got there first.

Since I was QRP at the time showing up late was often no better than not showing up at all. I updated and honed my pile up skills to overcome this handicap, and I seemed to do pretty well at it. However the value of listening is still there, if you understand how the game is now played. Listening is a way to catch the DX before the horde arrived, especially the majority who would only stir when there was a spot. The majority have, in effect, delegated the listening to others, including the skimmers.

The why of listening

There is of course the operating awards benefit of listening, that of getting there first and not having to contend with the pile ups. Modern pile ups are like the phenomenon of flash mobs, growing from nothing to a large crowd in a minute -- spotting networks are a kind of social media. Years ago it took time for the pile up to build since there was no instant communications to one and all about where the DX was located, or that a rare one was active.

That is not the only reason to listen. Listening is in itself a pleasure. When I was very young and first discovered the magic of short wave radio I liked to listen to signals coming in from all over. But I didn't have a receiver. Instead I would "borrow" the family 5-tube AM radio from the kitchen. I had learned that by unscrewing the slug in the local oscillator coil I could lift the coverage to well above the end of the broadcast band at 1,600 kHz.

There I heard AM broadcasters, commercial operations such as ship to shore and the odd pulsations of RTTY as heard through an AM detector. I also came across the rhythmic thumping of CW and the unintelligible squawk of SSB. That was how I first discovered the existence of amateur radio and hams. A ham license was still several years in the future.

After my listening sessions I would screw the slug back down, making sure to calibrate the dial to a local broadcast station, and return it to the kitchen. My parents were very tolerant of my burgeoning hobby. That is, as long as there was no harm to what was to them an expensive appliance.

My listening habit carried over after I was licensed. Some of that was out of necessity since I did not have much of a station: an 807 to a dipole 3 meters high. I enjoyed it immensely nonetheless. In a way I found more pleasure in discovering DX on the bands than calling and, sometimes, working it. As time went on my DXing, and then contesting, became more intense so that my listening had an objective: I was hunting more than listening.

Why do it now

I am happy to say that I have rediscovered some of that early magic. At times I find myself tuning the bands for no other reason than to hear what is out there, having no inclination to transmit at all. With the new Beverage antenna I can listen in on far more distant DX on 80 and 160 meters than before. Without a decent transmit antenna I cannot work them, so listening to them is all I can do for now.

With the return of the equinox comes propagation over the pole from south and southeast Asia. I enjoy tuning the bands from 40 meters on up to catch the openings and hear what I can hear. Often the signals are very weak and not easily workable. Either I don't have enough power or they are hearing others far more strongly than from this part of the world.

Of course I do sometimes come across some moderately rare DX, and that's all to the good. Just this morning I tuned across V85TL calling CQ on 20 meter CW and getting no callers at all. No one had yet spotted him. I worked him without much difficulty. Then I listened as his subsequent CQs went unanswered. The band was busy, with stations all around, yet none seemed to be listening. After a couple of minutes I spotted him and that drew in callers.

Modern times

I think it's a shame that too many hams nowadays don't listen. This is not about getting there first or sharing the burden of hunting down the DX and spotting it for others. What I find unfortunate is that too many seem to have lost the simple pleasure of tuning the bands and listening, and perhaps finding the unexpected. Not for awards or points but for the thing itself.

Do newer hams feel the magic of radio? Perhaps not in the same way, and that's a shame. Some of my own generation seem to have lost the magical feeling that drew them to amateur radio in the beginning, yet others I know still have it. There are hams I know who in their single-minded pursuit of DXCC Honor Roll will only stir to turn on the rig when a new one appears on the bands. That leaves me cold -- to me amateur radio is much more than that.

This is not to be critical of anyone or to make myself out to be a curmudgeon. Radio still has magic to it and I regret that some may have lost that feeling or perhaps have never had it. All I can do is shrug it off, feeling that they are overlooking something of value. I will keep listening.

Tuesday, April 4, 2017

Building and Tuning the Remodelled A50-6

Sporadic E season is rapidly approaching. We can expect the regular appearance of propagation on 6 meters beginning in early May. Unlike the previous two seasons I plan to be active with a far better antenna. Hence my remodelling of my ancient Cushcraft A50-6 to conform with the optimized design by W1JR in the more recent A50-6S.

With resumption of serious tower work still several weeks in future this is a good time to prepare antennas for the season. I can't even get to the Beverage termination to continue experimentation with it since the fields and bush are a boggy mess. Eventually the ground will thaw and dry, but that takes a while in this climate and our soil conditions.

For 6 meters antenna preparation is a relatively easy task since I have everything I need. Most of my other antennas require more extensive modelling, tooling and parts acquisition before construction can commence. So it was time to work on the A50-6 and get it ready to go.

The modelling went quickly, requiring no more than minor adjustments to my earlier work. The final design largely conforms to the A50-6S dimension. I lengthened the reflector, driven element and first 3 director by ~¾", and the fourth director a little more. Half element lengths:
  • Reflector: 59-¾"
  • Driven element: 54-¾"
  • Director 1: 54-¼"
  • Director 2: 53-¼"
  • Director 3: 52-¾"
  • Director 4: 49"
The first change moved the best gain performance to the bottom of the band where all my operating takes place. The second change boosts the gain ~0.3 db (by tightening the resonance range of the array) while having little effect on F/B and not degrading SWR below 51 MHz.

Element spacing is identical to the A50-6S. All dimensions were measured to within ⅛".

The original A50-6 design used equal spacing between elements. This can work well -- as shown by W2PV -- but not in this antenna! The W1JR optimized designed does much better although it does introduce mechanical considerations due to the clustering of elements at the rear of the yagi.


Before I could assemble the boom I had to straighten one tube that had a slight bend. This goes back to when I used the boom as a wire antenna mast a few years ago. The 1-½"tube with a more pronounced bend was repairable with the pipes I had on hand. A different technique was needed for the 1-⅝" tube. Looking around my large stock of material I found a 1" solid steel rod and a large tree that suited the task.

With straight edges and careful rotation of the tube in my workshop I precisely located the peak of the bend and the section of the tube that was curved. The peak was not at the centre of that section. I marked these points on the tube and went outside to visit the tree I'd selected.

The peak point was centred within the V where the trunk branched, conveniently at shoulder height. The steel rod was measured and inserted so the end was similarly centered. A small length of pipe collared the pipe where it exited the tube in order to minimize the risk of kinking the tube.

With everything in position I proceeded to push the rod until the tube yielded. It worked quite well. I then repeated the procedure with the bend point to one side then the other of the peak to smooth out as much of the bent area as I could. Although the result wasn't perfect you can only tell by sighting along the full length of the assembled boom.

A further problem with the boom is that the centre of gravity is off-centre. The A50-6S compensates for this by using a longer length of 1-⅝" tube on the long side of the boom. The A50-6 tapers to 1-½" for the last few feet. At some point I may want to replace the boom with heavier wall tubing to increase its wind and ice survivability.

Pointing straight up

As many hams know and as I described in a previous article a convenient technique for tuning yagis is to point them straight up. The reflector can be quite close to the ground, even 0.25λ can work well. The reason is that cancellation of radiation to the rear of the antenna reduced ground interaction. Keep in mind that all we're doing is tuning for best match -- not gain -- and that F/B has to be moderately good over the desired bandwidth.

I used EZNEC to model the antenna in this position to see the effect of ground and to determine how low I could safely go. I settled on 5' (1.5 meters, or 0.25λ) for reasons of available props, modelled performance, safe handling and accessibility of the driven element. The prop is a length of schedule 40 water pipe with a 1.6" I.D. which fits reasonably snugly over the 1-½" boom (plastic end cap removed).

I didn't use the Trylon tower as the support since the tower is very wide and could interact with the antenna more than I'd like. Instead I used a log frame in my backyard. I did my best to orient the yagi so that its elements were nearly orthogonal to the 80 meter inverted vee overhead and off to one side. It seemed to work fine even though I ought to have temporarily moved the inverted vee.

Notice how the coax is routed along the boom and straight down so that it doesn't interact with the elements. A temporarily common mode choke consisting of two cylindrical ferrites reduces the effect of RF conducted onto the coax outer surface.

Tuning it up

The antenna uses a gamma match for transforming the low impedance of the antenna to 50 Ω. In EZNEC I used an L-network since it is easiest to adjust in the model. These and similar networks have almost identical matched SWR curves so they can be considered equivalent. The EZNEC model optimized SWR curve for 50 to 51 MHz is quite good. I initially setup the gamma match per the A50-6S manual. That turned out to be a good starting point despite my design changes.

The objective is to see how well I can adjust the gamma match to get the same result. This assumes the SDC (stepped diamter correction) is done properly so that the real antenna and the model have the same resonance, and therefore the same performance metrics of gain and F/B. Since I've done this before and had good results I am confident that I've got a close match to the modelled performance.

It took about 30 minutes of fiddling with the gamma match until I got what I wanted. Each adjustment required moving a step ladder into place, making the adjustment (usually in ¼" increments) then moving the ladder away.

Look at the measured SWR curve and see what you think. Perfection isn't necessary since the environment for tuning is different form that atop the tower and stacked above an HF yagi. Further tweaking can be done then, though not easily since the driven element is far from the mast.

Performance note

Tuning an antenna for a match is at best an indirect indication of good performance; at worst it is totally misleading. Optimum gain and F/B per the model can quite easily be frequency shifted in the tuned yagi.

It is the shape of the SWR curve that is of more interest since it indicates that the rate of impedance change conforms well to the model. As an example, yagis typically show a sharp decline in radiation resistance near maximum gain. The rapid impedance change will appear in the SWR curve since the matching network cannot deal with these sharp swings and the SWR will soar. Too flat a curve is similarly an indication that something is amiss.

That the measured SWR curve is so close to the model gives me some comfort that the antenna performance will be as modelled is however no guarantee. That requires field strength testing.

Packing up

Declaring success I tightened all the adjustment fasteners and took down the antenna. It has been placed out of the way and off the ground until I am ready to install it on the Trylon tower. I have high expectations for this year's sporadic E season.

Sunday, April 2, 2017

Increase Your S & P Rate

Conditions for the SP DX contest this weekend were poor from my location. Despite the solar flux climbing above 90 there was nothing to heard above 20 meters and on 20 meters signals out of eastern Europe were weak and often had an auroral flutter. The combination of a disturbed geomagnetic field and a series of flares was unfriendly to propagation at higher latitudes.

While I struggled to make myself heard in the opening minutes of the contest I did hear evidence of extraordinary rates from several contesters in the US. Only 15 minutes into the contest some had serial numbers above 40 and 50, apparently S & P since they were calling SP stations. It was amusing to see these callers asked to repeat their numbers, which were unexpected so early in the contest.

Is this for real? I don't see why not. Skilled operators can have a very high S & P rate by in select times and places. I've done it myself back when I was QRP and surely not the biggest gun on the bands! I have achieved rates as high as 4 per minute on SSB and 3 per minute on CW, sustained for 5 or more minutes. It's intense and hard work, and in my case done without assistance from skimmer and DX spotting networks.

Let's look at how it's done. It requires skills that can be learned, if you are willing.

Speed and the big gun

You don't have to be a big gun to achieve a high S & P rate, but it helps! Ideally you want to get through on the first call while sending your call once and fast. Big antennas and power help with that. Fast contacts ensure that you are soon hustling to find the next station to call.

Less time spent in a QSO is a key ingredient to achieving a high rate. But don't sacrifice accuracy.

Don't dawdle

Even if you're not a big gun you should strive to be quick. On CW don't go slow! Send at the other guy's speed even if you have difficulty copying that fast. Assume they can copy as fast as they send because it's almost always true. Presumably you already copied his call so you're already mostly there and you need not feel intimidated.

On SSB it helps to use voice memories. There is a risk of talking too fast and poor enunciation when you're in pursuit of a high rate. Send a recording that has been thoroughly vetted for intelligibility and rapidity to avoid the need to repeat your call. Use phonetics and don't use unconventional phonetics.

At the end of the QSO don't stick around. As soon as I hear the "TU" being sent I am spinning the dial or clicking on a spot. Seconds count so don't waste any. Even when I tune in the next station I will not stick around if they are struggling with a QSO since that, too, wastes my time. Self spot it and move on. You can come back later.


With assistance you can save time between completing one QSO and pouncing on another station. Skimmers are best for this since many stations are not manually spotted if most people consider them to be uninteresting: for example, not rare and not a desirable multiplier. Skimmers aren't subjective so they'll tell you about everyone you have yet to work.

Clean slate: call first, copy later

At the start of the contest and every new band thereafter you have a clean slate; that is, every station you hear is workable. This is an opportunity to pump up your rate since you do not need to know the other station's call sign before you call: it cannot possibly be a dupe! (Well, except for the minority of contests where you can't work a station once per band.)

As soon as you hear the tail end of a CQ or QSO just jump right in and call. You can fill in the call after they work you, when they will typically close with "TU QQ9XYZ". This is a great way to increase your S & P rate, perhaps doubling it. There is no rule that says you must copy the call sign before you call them.

Occasionally the station won't sign afterwards but that is insufficient reason to defer calling before you get the call sign. Stuff the frequency in a VFO and move on to get it a minute or two later if you must. This is low risk, high reward operating. Go ahead and live on the edge! If you still fail at getting the call (they might even QSY) you can wipe them from the log. In my opinion they are at fault for not frequently signing.


By now you must have realized that these techniques can be considered aggressive, even very aggressive. However, this is about being aggressive in pursuing QSOs for a bigger score, not belligerence against other contest participants.

Push yourself out of your comfort zone and try it sometime. Watch the clock and count the seconds between QSOs. Meeting and overcoming challenges can be rewarding. The tension you feel comes from pushing hard. That's a good sign. Soon enough you can relax and return to normal operating.

Why do it at all?

Other than very short contests it can be argued that all this S & P hard work is unnecessary since rates eventually slow for everyone and you have the leisure to work stations later on if you haven't worked them earlier. You cannot count on this. Working them sooner rather than later can make the difference between working them and not working them at all.

In a contest where you must S & P you should therefore strive to do so at speed and as early in the contest as you can. Here are a few reasons why:
  • They might not be on later. Most contesters operate far less than the maximum allowable time.
  • Propagation can quickly deteriorate. If you haven't worked them yet you might be able to work them later.
  • Getting the relatively easy ones out of the way sooner gives you time to hunt down and work more multipliers or focus on marginal bands (e.g. 10 and 160) where you need to spend more time to make each QSO.
Being fast at S & P can be far more draining of your energy than fast running. To get consistently good results you need to be good at both. Unfortunately it is difficult to maintain that speed and you might only know if the effort is worthwhile when the contest results are published. But who ever said that winning would be easy?

Give it a try

I sometimes imagine how useful it would be to have a training tool like Morse Runner for S & P rather than just for running. Fast, accurate S & P is necessary for building up your contest scores, even if you are a big gun. It can also be a lot of fun.