Saturday, April 30, 2022

Direction Pot for an Upside Down Prop Pitch Rotator

Prop pitch motors make excellent rotators for the very largest antennas and rotating towers. The DC motor is powerful and the gearbox has exceptional torque and turns at just the right speed. What they lack is a convenient means to attach a mast and a direction indicator.

There are two ways to drive a mast -- I have one of each: 

In both cases the weight of the mast and antennas and radial thrust are supported by bearings. The motor is only designed for torque.

There are several ways to add a direction indicator to a prop pitch motor:

  • Magnetic sensor on the motor axle that pulses on every motor rotation. The motor spins at ~9500 RPM (0.1 ms per rotation) so the technical requirements are non-trivial. Perhaps the most common example is the control system sold by K7NV.
  • Magnetic sensor (compass) mounted on the antenna, which communicates by wire or, in some cases, by radio. There are numerous products available of diverse capability and reliability. One successfully used by a few hams that I know is the magnetic sensor sold by 4O3A.
  • Use a belt or chain drive around the mast to drive a potentiometer. I don't know of any commercial products, and most everyone builds it themselves. It isn't difficult but there are different methods. Making it mechanically and electrically reliable is the challenge.

I chose the last option since it's inexpensive and I enjoy home brew projects like this. The challenge was to design a belt drive system for the pot, which is unlike the method I used for the chain drive system on the other tower. 

Getting the unit built took longer than it ought to have taken because I fidgetted over the design and then winter arrived. Now it's done. It was a nice little project to start the tower season with. The system is simple, the details are critical to success.

We'll look at the belt and tower mounting shortly. Let's first review the details.

The C-shaped steel chassis was pulled from my junk box. It's the right size and it's rigid enough for the application. I didn't saw off the "lips" on the left since they aren't in the way. If you don't have a similar scrap of metal handy it isn't difficult to fabricate or purchase something similar. The hold down screws and nuts for the bearing are #6 stainless. The holes in the steel chassis are large enough to allow the inner ring of the bearings to spin freely.

The pulley was found in a local farm supply store. For the 2-⅞" mast, there is about a 2.5:1 drive ratio. The pot turns ~2.5 times for a 360° rotation. The 10 kΩ linear Bourns pot has a 10:1 reduction drive, so this equates to a 2.5 kΩ range, or a 3 VDC range with a 12 volt power supply. Doing it this way supports over-rotation and improves resolution when applied, with suitable voltage division, to the 10-bit ADC of an Arduino. Should I decide on a software controller of this type, the ultimate resolution is about 2°. That's more than adequate for HF yagis.

There are ¼" sealed bearings at the top and bottom of the ¼" aluminum drive shaft. There is no friction with normal or excess belt tension, and no radial force on the pot. The shaft is slightly oversize due to the mill finish. This came in handy since only the section that fits inside the bearings must be reduced. I mounted the shaft in a drill press and used a flat file to remove material. A metal lathe is the proper tool, but for this small job the drill press worked well. 

The shaft bottoms in the lower bearing at the transition from the turned down section. Those stops ensure the mast sits firmly within the bearings without slipping. The pulley has a ½" press fit bore. A reducer was made with 1" lengths of ½" and ⅜" tubes slit along their lengths. I have a box of tube scraps from my many yagi projects. The 5/16" set screw was fabricated from scrap screw stock by cutting a slot for a screwdriver. A few minutes of work saved a trip to the hardware store.

The bolt on the left connects to angle stock attached to a tower girt (see below). Moving the position of the inner nut adjusts belt tension. The hole in the chassis was already there and it was perfectly placed for the bolt.

The bracket for the pot must be carefully bent, drilled and attached so that the pot and shaft are aligned over the full range of rotation. I made the mounting holes larger than required for adjustment room. The bracket is made from ⅛" aluminum stock. Final alignment required careful bending in a vice to make the top and bottom faces parallel. The ¼" shaft coupler is a flea market special. In the final installation (see further below) I used stainless screws cut to size.

Here we see the completed unit mounted on a tower section that I keep as a jig in my workshop. The pipe is manually turned to mimic mast rotation.

As you can see, the belt doesn't need to be anything fancy! The friction due to the pulley, bearings and pot is so low that almost anything will do. The knot passes the pulley without any problem. I will eventually come up with a better belt. Initial testing suggests that the rope belt does not creep down the mast as it turns if the belt isn't measurably slack. I may add a thin flange around the mast to make sure that it stays in place.

Alternatives to a rope include a V-belt, an adjustable belt and a rubber band. Finding a V-belt of exactly the right size is difficult and there is no good way of getting it around the mast and pulley. The adjustable belts I've found online look promising but they are very expensive. I tried rubber strips from my junk box and found that the excellent grip caused them to easily derail by riding up the pulley rims. Rope is cheap, easy to fit and won't jump out of the pulley.

For weather protection, the unit is mounted on a tower girt to place it directly beneath the plate for the middle mast bearing. The pot is wrapped to resist corrosion from moisture, which is a common problem for pots located outdoors. The plate and girt should offer sufficient protection to the pulley and belt from wind driven, rain, snow and ice. I won't know for sure until it survives a cycle of the seasons. 

The pot slider is grounded, both to the tower and via a control cable wire. Several feet of Cat5 run from the pot to the termination of the main run of control cable. There I spliced the wires into the bundle. The other wires of the control cable are for the 15 and 20 meter stack switches.

The bit of scrap rope I used for the belt is temporary (ha!). It was about the right length so I carried it up the tower and wrapped it around the mast and pulley. That double granny knot is not going to last long! I just want it to last long enough for for the first phase of testing and experimentation. It is easy replaced.

Lucky for me, when I did the control cables for the 15 and 20 meter stack switches I made sure that all wires of the control cable were connected from the tower top to the shack desk. It was easy to turn over the "temporary" stack switch controls to access the 3 wires (pot slider is grounded) and measure the resistance as the motor is turned. So far so good.

Software controllers for the two prop pitch motors are an item in my 2022 station plan. I have the chips and other components, but not the software or hardware UI (user interface). I haven't yet decided whether to go fully with software, as with the ongoing antenna controller project, or a mix of hardware controls and software. I'll build a prototype or two before deciding on a final design.

Expect an article later this year once I have a prototype controller. It'll be nice to get the large and retro controller relegated to below the operating desk rather than adding to the clutter on top of the desk.

Saturday, April 23, 2022

More Cable, Another Trench

I've dug trenches to bury a many long runs of cable. It isn't an easy job so I always add extra cable for future expansion. Since predictions about the future rarely work out, I inevitably require more cable than originally foreseen. Hence, more trenches.

Last week I dug a new trench to the 150' tower. When the trench was first dug in early 2018 (cables were on the surface for the tower's first winter) I laid down 4 runs of Heliax, 2 Cat5 control cables and cable for the prop pitch motor. 

Since then, I fully occupied the second control cable for the Beverage remote switch, which itself required a new trench. Last year I ran a new cable for the side mount TH6 rotator. I used almost every other control cable wire for the rotator and for the planned 10 meter stack switch.

One of the Heliax runs is ½" flex, which is not rated for burial. The price was right, I was in a rush, and despite the inappropriate burial it is still doing well after 4 years underground. Nevertheless, a replacement for it seems wise with the new trench prepared. Another Cat5 cable joined the LDF5-50A, and of course the 14/2 cable for the Ham-M rotator.

Refer to the earlier article and you'll notice how the routes of the two trenches differ. The photograph and way points guided the route of the new trench. I realized I might need a second trench when I dug the first. I planned the route of the first trench to easily accommodate this, the second trench.

It's a good thing it's just hay in the field since the plants are perennials and there is no need for the soil to be overturned for planting. Disturbing the soil to that degree is incompatible with buried cables and radials.

The first trench was dug with a small trencher (there's a pic in that earlier article) that I rented for a good price. Although it did a fine job, it was heavy, tiring to operate and it destroyed the surface vegetation. For the second big tower, the trencher was no longer available and I had time on my hands since the pandemic lock down had just begun (spring 2020). I picked up a shovel and pick axe and got busy. 

It was a lot of work, but not as much as I feared. That 170' long trench contains 3 Heliax runs, 2 control cables and a spare cable for a future side mount rotator. When the sod was replaced the hay quickly resumed its spring growth. Trenches dug by the trencher were barren of hay for the first season.

Although I am not shy of manual labour it is no easy choice to pick up a shovel rather than rent power equipment. However, my source dried up so that an economical rental was not available. At the time I believed that I would merely save money by digging the trench manually. The advantages were more than I anticipated:

  • Low cost, if you have the time and endurance
  • By using a spade the sod can be saved for rapid surface remediation
  • There is no rush: work for an hour, rest and continue when you're ready, without regard to a ticking clock when you are using a rental
  • Save the time of trencher transport (if you do it yourself), maintenance and cleaning and dragging it around the property
  • Quiet and no exhaust fumes!

Despite not having timed myself, my guess is that the time investment is not very different for a shovel versus a trencher. Larger trenchers are self propelled, which would save time but those are more expensive. A shovel really isn't all that slow. If you are physically unable to do it, a trencher makes sense. 

There is no equivalent comparison for digging holes for tower bases since small backhoes make a mess. You'll likely need a wood form to pour the concrete. With a shovel you can make a "mud hole" that is far more precise and doesn't need a form. That can be well worth the effort of manual digging. You can also hire labourers to do it if you can't do it yourself. A trench does not need to be so precisely made.

In the trench picture at the top and the one at right (late fall of 2017), you can see water in the open trench. It inevitably rains before the trench can be back filled. Notice that the cables have been laid in the waterlogged hole regardless. 

If you feel leery about that, perhaps it's because you're not using cable that is rated for direct burial. Cable rated for burial will not be bothered by the open water or by saturated soil when it is buried. Spend a little more on the cable and you won't have to redo the job in a few years. That said, I often use unrated cable for low voltage AC and DC with an unblemished PVC jacket. So far so good, but don't expect miracles.

There are many stones below ground, both large and small. I remove the small stones but the big ones pose a problem. Most of the time I shift the trench several inches to route around them. Trenchers have enough power to remove many of the big stones that I wouldn't bother with when using a shovel.

There are other methods to bury single cables and wires where depth is not critical. In that first referenced article I demonstrated my mostly failed attempts to mechanically dig narrow and shallow trenches for radials. It did not make the job easier. It is better to lay radials on ground, pin them to the sod and let the vegetation grow to cover them. I have yet to snag a radial with the riding mower.

Another method is to slit the sod. I use the lawn edging tool shown at right. It takes very little time to cut a slot across the lawn. This is how I buried the burial grade cable for the new terrestrial wireless internet equipment that was mounted on the Trylon tower. It works best for narrow cables like Cat5/6/7 and RG6. It's impractical for thick cables and cable bundles.

Make the depth consistent since the half-round blade doesn't cut deep along its full width. Wiggle the tool to widen the slit. A length of thick steel (at least ¼") is used to push the cable into the slit. Keep a screwdriver or similar tool handy to cut the dirt missed with the edging tool. Do not bend or stress the cable by forcing it in. Clear the obstruction when you run into resistance.

One final job that I've been putting off for a long time is burying the multitude of cables from the stone wall surrounding the lawn to the Trylon tower. The weight of the cables adds up and it's becoming so heavy that I am uncertain how much more the aerial run with its steel messenger cable can withstand.

The biggest impediment is the 20 yd³ of topsoil in the way. It was there when I purchased the property and I gave it little thought at the time. A second problem is that the roots of the birch trees run close to the surface and they surround the wall. I've already had to deal with them on the outside of the wall -- the wall foundation isn't deep enough to block the roots. I cut the small roots and route around the larger ones.

The dirt pile can be moved with a small backhoe and I have a landscaping project that needs the soil. The birch tree roots are a more difficult challenge. It is unlikely that I'll deal with it this year. 

An alternative that I might choose is to increase the aerial run strength. A trench cannot solve all problems, and there is a benefit to having easy access to the cables for maintenance and station reconfiguration.

Friday, April 15, 2022

FT8: What's That Sound?

While I ever so slowly ease back into spring tower and antenna work, the technical articles are slow in coming. They will return! But for now I have another article about operating, and in particular about operating FT8. This is timely since 6 meters is intermittently open to South America and sporadic E season is a few weeks away.

Have you ever worn headphones while operating digital modes? Few do since there is usually nothing worth listening to. The software does all the work. About the only time I do it is when I want to quickly check 50.313 MHz for activity. When nothing is heard I flip back to HF and conventional modes.

Another good reason to listen is to monitor your own signal. Is the audio distorted? Is there power line hum? Is the microphone live? Almost all of us use SSB on our transceivers to operate digital modes, and our signals are subject to the same problems that are common on phone. I expect that rig technology will evolve to improve digital mode operation, but for now we must be careful since the SSB set-up is different for phone and digital.

Since SSB bugaboos have been discussed from time to time on the blog, I will only briefly mention a few items: disconnect the mic, disable the speech processor and keep the average power well below the CW or PEP peak power capability of your transmitter and amplifier.

Now let's move on to several items that seem to be increasingly common on the digital frequencies.

I hear voices

The FTdx5000 I use for digital modes has the front mic jack live at all times. The buffer amplifiers for the mic jack and rear audio input jack are mixed and there is no possibility to disable one or the other. Many rigs are similar. It is critical to unplug the microphone on the majority of rigs when digital modes are used. The computer software should be the only audio source.

Yet many forget. I do it occasionally since it is so easy to forget. Put on your headphones and listen to any busy FT8 channel and you will often hear background shack noises and conversations. Most hams realize their mistake and correct it. Unfortunately there are a few who never do and woe to those who tell them! Unless the signal is local and strong you may have difficulty identifying the guilty party.

You have mail!

Most of us use Microsoft Windows on our shack computers. Windows handles peripheral equipment with a great deal of flexibility so that it is responsive to the behaviour of most people. It deals with audio devices and sound cards being attached and detached, along with their various driver and configuration requirements. That doesn't always work for hams and others with very particular requirements for their audio devices.

Windows has a designated default sound card. It is typically on the motherboard, and uses the front or rear audio jacks. When there is more than one sound card, on the motherboard or added by the user, the default can be changed, and the change can cause problems. The default sound card is the one that Windows uses for notifications. These include the "bong" sound when you do something wrong, the chime or voice announcement when an email arrives, among many others standard applications. 

In most installations your digital software uses the default sound card. When Windows notifications occur during a transmission they will be transmitted. That's not good! There are ways to prevent it by delving into Windows settings or with additional hardware.

Since I don't have multiple sound cards on my current shack PC, my solution is to disable all Windows audible notifications. It works for me, though others may not like doing that. An alternative is to have two or more sound cards and use a non-default sound card for the rig interface. Many recent generation rigs include a sound card in their USB interfaces so you don't have to go out and buy one. If your rig has it, use it.

Courtesy tone

Modern transceivers have a plethora of features that almost nobody uses. One that should never be used on HF is the courtesy tone. This is the feature that transmits "beep!" when you release the PTT. It was popularized decades ago on VHF/UHF repeaters to make explicit when a transmission was over. The use of squelch on FM can make the end of a transmission difficult to deduce without it. On SSB it is not necessary and, in my opinion, it sounds ridiculous.

When you switch to digital modes, of course using the SSB mode of the rig, the courtesy tone feature is applied if enabled. In most instances it does not cause QRM because everyone's transmissions are synchronized. However, it is still poor operating practice and locals in particular will have no difficulty identifying the culprit. Don't use the courtesy tone feature and this won't happen to you on FT8.

Text to speech

We have some wonderful tools at our disposal to improve our results at gathering DXCC countries, grid squares, states and many other awards. The ability to passively monitor all activity on an FT8 channel can be exploited to further those aims. There are software applications that will monitor the messages decoded by WSJT-X, look up the call signs in local and remote databases, and issue notifications when a station is needed for one of those awards.

Many times I've heard these announcement on FT8 channels, and in one case from two stations at the same time. Not only does this interfere with others, it also halves the periods that you are monitoring since the transmissions exclude the possibility of listening during those periods. Unless you can route the notifications over a different audio path than that for the received audio, turn off those features.

Voice announcement features of modern transceivers can also be a concern. Features that are so useful to blind hams have found use in many shacks. With the features enabled, the rig will audibly announce the frequency, mode and other data. Depending on how the audio is routed between the rig and PC, these announcements can inadvertently be transmitted when using digital modes. 

Every rig is different and I don't have or use these features, so I cannot offer a recommendation other than to turn them off when you don't need them. For audio routed to the PC on digital modes, you might not even notice that it is happening unless you check for it.

Sound card shuffle

Among its many peculiarities, Windows is notorious for reordering, renaming, reconfiguring and renumbering peripheral devices during periodic updates and sometimes over a PC restart. It isn't noticed by most people since it doesn't affect their use of the PC. It is difficult to predict when it is likely to occur. You must be observant.

As mentioned earlier, Windows usually does it to transparently deal with what it believes are potential trouble points. With our particular computer interface needs in the shack, we need to prevent or recover from what Windows chooses to do.

With digital modes pay particular attention to sound card names and ordering. With many sound cards, it is a good idea to check the default and sound card assignments after Windows updates. There are security products that can disturb your configuration and those settings will need attention as well.

Monitor your transmissions

Almost all of the aforementioned problems can be discovered by monitoring the transmitted audio. Use the rig's monitor feature from time to time to ensure that the transmitted audio is clean and uncluttered by extraneous audio sources. This is especially important after you've made configuration changes on your rig, PC or software applications. It isn't something that needs to done all the time so it shouldn't be a burden.

It is sad to say that few hams pay attention to their transmitted signals, be it to check for distortion, key clicks or inappropriately routed audio. In some cases it is necessary to listen on a separate receiver since not all potential problems can be heard using the rig's monitor feature. Alternatively, ask a friend to listen and let you know if anything is amiss.

Thursday, April 7, 2022

CW Competency

I have an admission to make. Although I love CW, use it a lot (starting in 1972!) and I can comfortably operate at high speed in a CW contest I am not a very good CW operator. Outside of contest exchanges my sending is often full of errors and copying ordinary conversation text is not great.

The problem isn't really lack of ability but lack of practice. When I use it a lot in daily operating, as I did early in my ham life, I do better. I no longer practice at high speed very often. Some evenings I will listen in on a high speed CW QSO -- 40+ wpm -- to see how well I can do. Depending on my mood and alertness I often do pretty well. 

Sending is a different problem. Outside of the 20 to 35 wpm range my error rate climbs. Both high and low speeds are difficult because my fingers are unable to get the timing right until I adjust the speed at which my mind is thinking. During conversations, I make flubs when I think of the spelling of words or I lose track of the sentence because it's so much slower than spoken conversation.

In the heat of a contest my ability to copy fast CW improves. Everything is fast in a competitive event and my reaction time improves. QSOs are structured and there are few times one has to send or copy anything different. Jumping on the paddles at that speed can be comical as I struggle to move my fingers side to side rather than up and down on the keyboard. I do better to avoid the paddles to keep my sending clean. 

About the only time I hit the paddles is to greet a friend or to send a partial call while running. I avoid even that when I do SO2R since I am not always certain which radio the paddles will key. Like most contesters, I strive to use the paddles as little as possible.

All that said, am I really so bad a CW operator? How should one assess ability and performance? You and I may have passed a code test years ago, but that says very little since the speed was slow and the content uncomplicated. 

It is surprisingly easy to get by in a CW rag chew by bungling up to half the characters received (or sent, for that matter) since context allows us to fill in the rest. When we only respond to the bits we did copy, our QSO partner will usually be none the wiser, and vice versa.

The difficulties I run into during a CW rag chew -- I'm mean a real conversation -- include:

  • CW is far slower than a spoken conversation or reading text, and I often lose the thread of the received sentence by the time it reaches the end. This applies to sending and receiving
  • Poorly sent CW makes me puzzle over a character or word group, and I may then lose the context or the gist of the sentence, or I miss the next several characters or word and so lose it entirely. These sending errors include run together characters and words, backing up to resend a word in which a error was made without an indication that that is the case
  • My attention wanders since the flow of the conversation is so much slower than when spoken. That causes more mistakes.

I am far from alone with these difficulties. That said, I do well in CW contests. In those events there is no rag chewing so those problems don't apply. The pace is fast and I can stay focussed for hours at a time. CW competency is measured differently in a contest:

  • Copy a call sign or exchange (some are quite complicated), at high speed the first time
  • While running, copy one complete call on the first try when many stations are calling and there is QRM or QRN
  • While spinning the VFO, copy a call sign on the first try, identify the station as having completed a CQ or at the end of a QSO, and make my call immediately
  • Pull an exceptionally weak station out of the noise level and correctly copy the call sign and exchange
  • During SO2R, interleave two CW QSOs and, when receiving on both radios at the same time, copy call signs and exchanges of both

Since I am better in contests than in coversations, am I a competent CW operator? If I'm judged to be lacking in competency in either category, am I truly competent? When I jump on the paddles to send something not in a pre-programmed message and I mess it up, is that incompetence or just momentary clumsiness?

Competency in any skill is a matter of practice and critical self examination. Without self examination, no amount of practice will help. Tune across many very active CW stations and you will find at least a few operators who have probably never listened to themselves and remain blissfully unaware about how hard they make it for others to copy them. I wonder if they care. There is no hiding from poor copying ability and that is what many focus on rather than accurate sending.

There is no need for perfection. It's a hobby and CW is a pleasant if archaic method of communication. It is not obsolete in amateur radio since it has the same advantages for weak signals and crowded band conditions that it had a century ago. It particularly shines in contests and DXpeditions by neatly sidestepping accents, languages and QRM. 

CW remains my favourite mode despite my inconsistent use of it and rare engagement in rag chews. But when I do use it, I love it. When it comes to competency, it should be no surprise that I am more interesting in improving my contesting effectiveness. My rag chewing CW skills lag and may never improve. My conversations are done with SSB.