Tuesday, December 12, 2017

Topping the 150' Tower

At long last the big tower project is substantially complete. By "substantially" I mean that a few small tasks remain although all the antennas are in use and rotating as they should. This project has taken quite a bit longer than I anticipated or planned for so not everything planned has been accomplished. Even so I am pleased (and relieved) to have achieved this milestone.

In an earlier article I described getting to the point of having the tower complete. Now I'll talk about the process to make it operational; that is, with working antennas. One disappointment is that I was unable to light up the top yagis in time for the CQ WW CW contest.

Time pressure

As the saying goes: time waits for no man. Back in August I was feeling pressured by the approaching winter when major tower and antenna work is out of the question. Even with this foreknowledge I failed to do all that I wanted.

My primary constraint was people. A lot of manpower goes into this size of project. You can either hire people or rely on friends. As the ham population ages the ability to solicit help declines, and many who are enthusiastic and willing are not physically able to do so. Hiring professionals is no panacea since everything must be prepared in advance and any mistakes or gaps will result in substantial additional costs.

Ultimately I ended up relying on myself and on friends. You can never have too many friends! Cherish them and return the favour of their assistance.

Antenna complement

With the calendar inexorably advancing I shelved plans for yagi construction and went with what I had on hand. Those yagis and a couple of wire antennas to give me the required coverage for effective contesting and DXing are what I have for this winter season.
  • Cushcraft XM240 at 47 meters: I made a few changes to the antenna since it was on the Trylon tower earlier this year. I'll cover this in a separate article.
  • Hy-Gain TH6 at 44 meters: With no time to spare I put this ancient antenna up top for low angle, longer path DX on the high bands. The antenna was refurbished, including trap repair, new trap covers and replacement of the Hy-Gain balun with one from Balun Designs.
  • Hy-Gain Explorer 14 at 34 meters: The antenna is fixed on Europe. It works well enough for a short boom tri-band yagi, though it is not what I had in mind. Next year it will be replaced by a more suitable set of yagis for the important European path.
  • Fan inverted vee for 40 and 80 meters with apex at 32 meters: The 80 meter vertical array is a winter project and there was no time to build a wire or tubing yagi for 40 midway up the tower. This is my solution for the winter, after which I plan to remove it to make room for a more permanent high performance solution for 40 and 80 meters.
  • T-top vertical for 160 meters: The antenna is simple and surprisingly effective with only 8 radials. If I'd known how well it worked I would have planned a more serious effort in the ARRL 160 meter contest. Now I am looking forward more cheerfully to upcoming contests. This is a winter antenna that will be taken down in the spring. I don't yet know if I'll put it up again next autumn.

XM240 in flight, with integrated boom truss I've been so busy and the bands less than stellar that I have not yet had opportunity to thoroughly test the antennas, especially on bands where I now have two or three choices. There are some expected behaviours and some that were unexpected. This is a subject for a future article.

The prop pitch motor is working well so far. I attached the direction indicator potentiometer on my final tower climb and it will be wired up to the shack controller shortly.

Tram line, again

Raising the TH6 and XM240 with a tram line was similar to how the Explorer 14 was raised. The important differences were the greater weights of the yagis, larger size and top attachment to the mast rather than the tower. These all require changes to the procedure.

First, the ground anchor must be moved further out from the tower so that the tram line angle is similar or even lower to maintain or improve, respectively, the mechanical advantage. I had 300' feet of steel cable on the reel and I used it all. I was close enough to a small forest area that I considered using a tree for an anchor rather than my lawn tractor. That would have required a winch to set the tension, which in the time available was an undesirable complication. As it was we were challenged by the autumn dampness which reduced the tractor's traction in the hay field. It needed manual assistance to set the tram line tension.

Hauling yagis up the tram line
Rigging the antennas for balance and centering required more care due to the greater sizes of the yagis. This was the most time consuming part of the procedure. The XM240 has the added complication of attaching the fragile capacity hats after the antenna is off the ground. Since the yagis were substantially heavier there were two people on the haul rope.

The XM240 was lifted low on the mast and raised afterwards to the top. There is a substantial bending moment on the mast which would require a back stay to make the tram line mechanically sound. I chose to keep it simple and not use a back stay. Once the XM240 was on the mast and tested with an antenna analyzer I climbed the mast to install a pulley at the top and thread another rope through it.

When my crew returned the following week I tied the haul rope to the mast rope and with their muscle I lifted the yagi to the top of the mast. In comparison lifting the TH6 immediately afterwards was straight forward.

Fixing problems

As you might expect not everything went according to plan. One of the stainless steel saddle clamps was damaged while fighting the TH6 into horizontal orientation. The threads were greased and (although I know better) I compensated for incorrect position with extra torque on the wrench. The threads galled. A few days later I went up with another clamp and a tap to either replace or repair the u-bolt threads. I was able to save the clamp quite easily by chasing the threads.

The TH6 boom truss turnbuckles were threaded a few turns and taped to the boom. A turnbuckle and one of its screws unwound itself and fell off. They somehow survived the 150' fall without any visible damage and with the threads intact. After cleaning the boom truss was completed a few days later. The less on to secure turnbuckles and their screws better for the lift.

After the yagis were up for about a week I went up to do some work and got a surprise. One of the shims between the lower and upper masts worked itself loose, moving upward and falling to the bearing plate.

I put it back and found that it fit loosely. The next time up the tower I brought along a muffler clamp to hold down the shims so this wouldn't recur. This is a good reminder that the lateral force on the mast due to wind on the yagis is substantial. I was not surprised that the shims would gradually deform under the force to match the mast curvature, but the way that shim got pushed out of the splice was a surprise. Perhaps next year I'll revisit the shims.

Lifting coax and cable

Coax and wire cables are surprisingly heavy when measuring 130' (40 m). They are not so heavy that lifting is difficult, the concern is that the cable will be damaged when hanging by its own weight. Even LMR400 must be treated with care. LDF5-50A Heliax (⅞") requires special measures.

I cleared one of the tower faces of obstacles to clear the way for the lift and ensure the Heliax would not encounter any sharp bends. Due to the position of the side mount brackets and the need to avoid the climbing face this left exactly one choice. Unfortunately that side held the large drive unit for the prop pitch motor at the 140' level.

I mounted the pulley immediately below the drive unit. The Heliax would pass through one strut and terminate just below the top of the tower's north side, and there attach to the rotation loops. To accomplish this Heliax was lifted from a point 10' to 12 ' below the top. The rope is taped at intervals above that to protect the cable from interference and damage. The N-connector is covered with a cap designed for this purpose.

Andrew sells cable hoists that wrap around the Heliax and distribute the load equally around the circumference over several inches of cable length. I don't have one. Rope can be used to achieve the same requirement with a coil of many turns, wrapping the end so that the rope can't unwind and ensuring that all knots and bends are on the outside of the coil. After each lift I inspected the cable to ensure there was no damage, not even scuff marks or scrapes on the jacket.

The cable threads between the Explorer 14 boom and tower. This was accomplished without duress. When the cable approached the pulley I climbed the tower. There I removed the tape wraps one at a time from the top as my helper on the ground lifted the cable in short steps. Once in position I spliced it to rotation loops and worked my way down the tower securing the cable at every tower diagonal. If you use the Andrew mounts (expensive) you can get away with intervals up to 5' or 6' depending on wind and ice loading.

For major installations such as this I strongly recommend mechanical and electrical tests of every section of feed line once the connectors are attached. At the very least use an antenna analyzer and a dummy load to check that the impedance or return loss is as it ought to be across the widest possible frequency range. Once it's installed and a problem is discovered it is very difficult to isolate and deal with. Don't take shortcuts. I also recommend using the best quality products to protect connectors and splices from the weather.

Cable on the ground

Temporary overground cable runs
Each run of feed line is in two sections: Heliax from the switch box near the house to the tower; LMR400 or Heliax up the tower to the antenna. I acquired numerous 100'+ lengths of LMR400 as reel ends from a local supplier at a discount for this purpose.

Since the side mount antennas (Explorer 14 to Europe and 40/80 inverted vee) are temporary I used the full lengths of LMR400 and coiled up the extra. I preferred this to cutting the cable to length to "future proof" to avoid the risk of waste when it is redeployed.

As I type this the cables cross the open hay field above ground. Digging a trench and burying them had to be deferred, on advice of the renter, because the trencher would cause clumping of the half-frozen soil, freeze when exposed and then not settle properly when the soil is pushed back in. I may yet get this done before Christmas once the weather rises above freezing. In the yard I expect to have an aerial run for the cable since burial would encounter too many obstacles.

Not yet tidied up
Switching

The 2x8 antenna switch is installed at the base of the Trylon (70' tower). This proved to be a convenient termination point for the many coax runs, including those on the Trylon itself. This unit has all the connectors on the bottom, making it easy to build a weather cover. The tower provides support for the housing and cable terminations. Heliax cables are terminated with jumpers to the switch box to avoid having to contort the Heliax and to make it easy to transition from N to UHF.

There are two runs of LMR400 to the shack, plus existing runs for non-contesting antennas. Managing cables this way is much easier than terminating everything indoors and grounds inactive antennas well away from the house. I believe this is a good trade off with having to install and maintain switching boxes outdoors. It will only grow more complex as I add more antennas to my antenna farm.

I'll have more to say about switching in a future article. It can get complicated.

Finishing and clean up

As I descended the tower the final time after installing the last Heliax run and attaching the direction indicator for the prop pitch motor I stripped off the tower what was left of the rigging. This was little more than a pulley and the 100 meter long haul rope.

Short path to east Asia on 40 through 10 meters
While I finished attaching the Heliax to the tower my helper coiled the rope and cleaned up the area around the tower. We left everything tidy. All the cables were given one final test, final splices sealed and all tools and material carted off and stored. I even swept the garage clean.

With that and some on air testing of the antennas the tower project was declared complete. Of course there will be much more to come next year, but this is nevertheless a major milestone. I am very happy with how far I've come and the obstacles overcome.

Aftermath

Winter projects have already begun. The base is in for the 80 meter vertical array and the new PC is configured for contests. Yet there is much more in my plan.

How far I go this winter will depend on the weather and my inclination. Some rest and relaxation is planned, or at least turning to non-ham projects and activities long put off.

I committed to give a February talk to local contesters and DXers on the subject of building my new station. That should be fun.

Right now the snow if falling and the north wind blowing. This is a good time to switch on the radio to use and enjoy what I've built. That's what this is all about.

Wednesday, December 6, 2017

Dog Days of December

For many people in this wintry climate, myself included, the closing weeks of autumn can be a time of low energy. It is brought on by the lack of sunlight, rapidly worsening weather and, perhaps, the excess commercialism in advance of the holiday season. As a ham at this point in the solar cycle there is less refuge in the shack since the openings are short and often fail to coincide with our busy schedules.

Yet there are contests aplenty, and still tasks to be done before the big tower project is finished. In between there is operating to be done and fitting in the rest of life. Despite some inevitable lassitude and exhaustion I'm keeping busy. All that said, let me briefly take you through the things that are not helping my mood this dark, cold December.

DXpedition lull

There was a great flurry of DXpeditions in November. Most of those are now done, many having been trips to operate CQ WW CW from a rare multiplier country. There is the usual potpourri of DX on the bands, though not quite as much to cause excitement. That said I did get a thrill catching a not-a-DXpedition 7Q7 on 40 meters.

The excitement will return in January with quite a few DXpeditions planned to very rare and moderately rare entities. That, the deep cold of winter and increased sunlight are sure to spark my enthusiasm.

CQ WW CW is past

CQ WW is unquestionably the highlight of the annual contest calendar. Now they're done. There is an inevitable letdown in the immediate aftermath. I expect the excitement to return once we get closer to the ARRL DX events early in 2018.

I put in a modest effort in the ARRL 160 meter contest last weekend, more to try out my new 160 meter antenna and new equipment within the shack. My expectations should not have been as low as they were since the antenna works surprisingly well. In retrospect I should have operate more hours than I did.

I finally got the new contest computer set up which is a tremendous improvement over the ancient Vista laptop I used in the shack since returning to the air in 2013. My antenna switching system also works well despite being entirely manual. I am getting ever closer to SO2R.

Low band challenges

Low band aficionados love QRN-free winters and the bottom of the solar cycle. It is certainly true that 80 and 160 meters light up with activity and even throw some juicy DX our way. On the downside is that even when conditions are good the low bands are a challenge.

Constantly digging signals out of the noise is fatiguing. Timing sunrise and sunset openings to the far side of the world, while exciting, is disruptive to one's life and sleep pattern. It takes getting used to. Yet what can one do when the MUF to anywhere interesting drops below 7 MHz mid-evening. It's the low bands or nothing.

6 meters

There is a winter solstice sporadic E (Es) season. Unfortunately it is far less intense than the summer Es season. I've listened a bit to the activity when I see spots on the cluster but have yet to transmit. Working the same old stations motivates me very little.

Winter projects

There are many antenna projects that can be done in the coldest months. Last winter I put up my northeast Beverage in February. This year I want to add Beverages for other directions. I also plan to begin construction of a directional 80 meter array. Lots of planning has been done and the north field has been surveyed with the placement of the tower (driven element) and parasitic wire elements.

Despite the long list of winter antenna projects working outdoors in the snow and the wind is not all that pleasant. Although I enjoy winters and being active there is a significant difference between, say, snowshoeing, and antenna work. In one you're constantly on the move generating body heat, while in the other you quickly chill while moving slowly and doing detail work that must often be done with bare hands.

The trick is to alternate indoor and outdoor work to keep it from becoming a miserable grind. It also takes a few weeks to psyche myself to take the plunge to get out there and get it done. That means January. On the bright side there are no black flies or mosquitoes.

Upcoming

Despite my long list of woes there will indeed be a great deal of activity this winter. As I write this the big tower project is several day effort to completion, weather permitting. It will be nice to enjoy the fruits of my labour (and that of many friends) over the winter months. You will see a few articles coming up on topping the tower and discussing how the various antennas play.

Work inside the shack will continue apace. I intend to become SO2R and low-power multi-op capable before spring arrives. Additional work for the future will add the switching and filtering for high power, and more automation. You can get away with little filtering and other things when you stick to 100 watts in the contests.

My 2018 plan remains sketchy at present. I will return to this topic in January.

Tuesday, November 28, 2017

CQ WW CW: The Good and the Bad

CQ WW is arguably the biggest event on the contest calendar. My station was in poor shape for the SSB contest at the end of October and I hoped I'd have everything ready in time for the CW contest this past weekend. I didn't quite get there despite a big push in the final hours preceding the start of the contest on (our) Friday evening.

The most glaring hole in my station is that I was unable to run coax up to the yagis atop the big tower. You can see in the picture that they are up there sitting pretty, tuned and rotating, serving only to tease me. I ran out of time. At the last moment I had to choose between putting up a 40/80 inverted vee or one Heliax run. With nothing else for 80 meters I opted for the inverted vee.

In a way I'm complaining about nothing of importance. It's just that I know how much better I could have done had I completed the antenna work. As claimed score reports flood into 3830 it's clear that I did very well in comparison to others in my class and geographical region -- Single-op; All bands; Low power. Something worse happened to a local big gun who suffered a concussion that ultimately took him out of contention. I could only offer sympathy when we spoke before the contest. Health is more important than anything.

What follows is a detailed breakdown of my experience with the station as it was this weekend and what I learned. That will inform my future plans. I kept a notepad within reach with which to take notes so that I wouldn't forget. Items of significant importance I will delve into in future articles.

So sleepy

The rush of tower and antenna work left me exhausted. Climbing and working on towers is physically demanding, even more so in cold weather. When I sat down at the radio after the evening meal to configure the logging software and test the antenna switching I nearly fell asleep.

I made it through the first evening on caffeine. Since I needed sleep I missed the start of the 20 meter band opening Saturday morning. I didn't feel truly rested until Tuesday.

Computer

I put off buying a computer until the big sales immediately before the contest. The computer was already selected but deferred for the discount I was told was coming. Unfortunately it was out of stock when I did make the purchase on Thursday so I could only leave with the new display and accept delivery of the computer after the contest. However the discount was very attractive.

Instead I relied on my ancient laptop running Vista. The Wi-Fi is dead as are all but two USB ports. Since it decided to stop talking to my USB hub a few weeks ago I had to disconnect the mouse and had to deal with my palms riding the track pad while typing. That caused occasional odd behaviour in the logging software. The working USB ports were needed for the FTdx5000 and WinKeyer.

This PC is a liability since it doesn't have the RAM or processor capacity to open more than a few N1MM Logger windows, or windows that update frequently. For example, I cannot open the band map to see my self spots. Instead I relied on the rig's memories and VFOs to mark stations I wanted to work later.

Oddly enough the laptop chose the very next day to finally try to catch up with dozens of Microsoft updates that it seemed unable to process for several months. Perhaps it knew that it was about to be put out to pasture.

Inverted vee for 40 and 80 meters

Since I am behind in my project to build an 80 meter vertical array, and there is no feed line yet to the XM240 I decided to throw together a two-band inverted vee for 40 and 80 meters. It is a temporary antenna designed to get me through the winter season.

The core of the antenna is the 80 meter inverted vee I put up on the Trylon last winter. To this I added a 40 meter inverted vee I had on my tower back in Ottawa. That is, it's a fan wire antenna using PVC pipe sections to hold the wires ~18 cm (7") apart. The apex is ~32 meters on the big tower, a few meters below the Explorer 14. The ends are held down by rocks in the hay field, far enough out for the interior angle of the vee to be ~100°. If you look carefully you will see the tower mount in the picture above. The wire and spreaders are especially difficult to pick out.

There was no time to tune the antenna since it went up only hours before the start of the contest. We could do no more than put it in place, untangle the wires and connect a spare run of LMR400 to a 60 meter run of FSJ4 flexible ½" Heliax going back to the switch box.

As expected it tuned well on 80 meters but not on 40. Due to capacitive end effects between the higher band element and the longer one the 40 meter inverted vee is electrically longer and resonates below 7 MHz. In the minutes before the start of the contest I trained the rig's tuner throughout the 7.0 to 7.1 MHz band segment and did a quick comparison with the multi-band inverted vee on the Trylon.

For most DX the higher inverted vee was 1 to 2 S-units better. On US stations the lower one was equal or better on stations in the US northeast (very short path). The higher one was better on the majority of US stations. On 80 meters I had nothing to compare with other than the Beverage on receive, from which little or nothing can be concluded. I fared poorly on both 40 and 80 meters in the contest, apparently more due to propagation than my antennas since others suffered similarly.

The antenna works though obviously not so well as what I had planned for 80 meters and not what I should expect on 40 meters once the feed line is connected to the XM240. I estimate that I'll get another 2 S-units for the yagi from a combination of height and gain. The inverted vee is needed for the winter to provide an omni-directional option on 40 meters to switch to when needed. It will be interesting to compare when the 80 meter vertical comes online this winter.

Side mounted yagi to Europe

Most hams who put up a tri-bander have one similar in size to the Hy-Gain Explorer 14. The boom is short at only 14' (4.2 m), having 3 active elements on 20, 15 and 10 meters. If it's all you have it is possible to be perfectly happy with it and work the world; it performed well enough to help win two CQWW plaques for QRP contesting from Ottawa. When you have another antenna for comparison the compromises inherent in a short boom yagi become apparent.

The antenna is fixed at ~35 meters height and a heading of 45°, towards Europe. It is much higher than the only other high band antenna I had for the contest, a TH7 up 21 meters. Height helps though not as much as desired. Before the contest I rotated the upper yagis towards north to, in part, minimize any detrimental interactions between the still unusable TH6 and the Explorer 14. That both antennas use identical traps assists with a direct comparison since element loss is similar.

On 20 meters, there was little difference between the Explorer 14 and TH7 towards Europe. Although disappointing this should not come as a surprise. Yagi gain is primarily a function of boom length, not number of elements; both antennas have 3 active elements on 20 meters.

The picture changes on 15 meters. Despite the longer boom and an additional director on the TH7 the higher antenna is clearly superior by at least 1 S-unit. That was welcome since at this point in the solar cycle the European openings on 15 meters are not as strong or deep as other times. Regrettably there was no opening on 10 meter so that comparison was impossible.

F/B is poor enough on 20 and 15 meters that I could work many US and Caribbean stations while focussed on Europe. The price is increased QRM while running Europeans. On balance I can't decide whether this is a curse or a benefit.

This is a temporary antenna to get me through the winter contest season. Because my tower project lasted longer than expected I had to rely on the antennas that were close at hand. In the spring it comes down to be replaced by...something. I'll be exploring options over the winter based on my experience with a selection of yagis at different heights.

160 meters

My results on 160 meters were similar to 40 and 80 meters primarily due to poor conditions. I continued to do well in the pile-ups on DX towards the south and worked as far west as Hawaii. This was with a 3 db handicap since I had to dial back the FTdx5000 to 100 watts from 200 watts to qualify for the low power category.

What frustrated me was little success towards Europe during the contest, managing to work only a handful. Did the antenna have a serious failing despite modelling that showed only a modest impairment in that direction? I was relieved to discover after the contest that I was not alone, with everyone on this side of the Atlantic Ocean having the same experience.

The answer may be that QRM and noise levels happened to be worse than usual in Europe. After the contest those woes continued. I did manage to work 9G5W despite copying difficulty on their side of the QSO. It may be that my only permanent solution for top band success will be an amplifier.

Antenna switching

When I picked up a secondhand 2x8 antenna switch a few months ago I accelerated my plan for SO2R and remote switching. Although I fell far short of SO2R for this contest I did complete the basics for switching antennas.

All transmission lines terminate at a tower base where there is a housing for the switch. Control lines run back to the shack along with two runs of LMR400. This is mostly a temporary setup since the coax is not rated for burial.

Switching is entirely manual rather than rig or software controlled. I quickly built a control box with only one side active. The numerous "blanks" are there for future control of an 80 meter array direction and Beverage selection. Or I may go entirely software control.

I'll have more to say on antenna control and automation in future, which is a complex and important topic. For this contest I kept it simple, and it worked fine.

Empty calories

As the contest progressed and I knew that I'd fall short in my quest for multipliers I altered my strategy so that I could still turn in a competitive score. I didn't yet know that others were suffering similar propagation woes, and that the fault wasn't not entirely due to me or my half-built station.

With multipliers difficult to come by I spent many hours ignoring the chase entirely to instead park on a frequency and call CQ. My intent was to work as many US stations as possible, on every band that was open. These QSOs earn fewer points and are free of any multiplier value. For the Americans it's a win since they get an easy QSO in the log.

Since I look upon CQ WW as a primarily DX contest these QSOs feel a bit like the empty calories in our diets that frustrate nutritionists. They're filling but not optimal to our health. I appreciate every one of these QSOs yet feel that I'm missing out while I'm filling up the log. Yet it's a necessary step to a high score. Unfortunately for the US contesters it's an asymmetrical dynamic since they far outnumber Canadians. This is a contest in which scores between US and Canadian entrants are not comparable.

In between or even during runs I would check other bands for multipliers. This is how I worked a few unexpected multipliers on 10 meters, which was barely open, and then only occasionally.

Here, have a peanut

I'm the sort of person who is always snacking. Especially when the rate slows I am sorely tempted to run to the kitchen and grab something to eat. Since I've been gifted with a particular metabolism there is no threat of weight gain! However the temptation can impact results if it takes me away from the rig.

My solution is to keep a container of trail mix at hand. I use it as a reward system. If a run is going particularly well I'll grab a few seeds while the computer is sending a message. I'll eat a tastier nut when I score a multiplier.

It may seem silly but it works to keep me focussed and in the chair.

Epilogue

After a big contest I enter a several days long lull during which I tend to avoid getting on the air or doing anything radio related. Very soon I'll return to working on the station. It's a big, challenging project and it's clear that even with carefully thought out priorities I won't achieve all I planned in 2017.

Winter is an opportunity to relax, do a lot of operating and contesting and less challenging antenna work and improvements in the shack. I'll be busy without the same frenetic pace. At year end I'll do my usual annual review and look forward to the coming year. There's lots of hard work ahead, along with joy of learning and achieving my goals. 

Sunday, November 19, 2017

160 Meter Antenna, at Long Last

One of the great advantages of a big tower is that it is downright trivial to put up simple wire antennas that perform well. I have now built the 160 meter T-top vertical I modelled earlier, tuned it and put it on the air. It works great for a temporary antenna. Next year I'll roll up the radials and store the antenna during haying season.

Choosing a permanent high-performance 160 meter antenna is not a priority for this year or next. I hope to get to it eventually.


The picture of the upper part of the antenna is annotated since it is otherwise difficult to see the 14 AWG wires. With radials attached it resonates at 1.750 MHz. This is 80 kHz lower than in the model, or 4.5%. That's a lot! Using percentage is helpful since a few kHz of error is deceptively small at low frequencies. Perhaps there is more coupling to the tower or guy segments that the model dealt with, or perhaps the ground differs markedly that what is in the model or that NEC2 can accurately calculate.

For a single element antenna of this type the error is not critical -- there is no F/B or main lobe to optimize -- so I trimmed the 22 meter vertical wire down to the designed 21.5 meters and compensated the rest with an L-network. The L-network is required in any case due to the low radiation resistance. Low radiation resistance is a feature not a bug, as we'll see.

Design departures

I did not follow my original design exactly. The biggest change was to reduce the radial count from 16 to 8. For a temporary antenna I did not want to take more trouble than absolutely necessary to get an acceptable signal. The radials are as designed: 30 meters long. It only makes sense to go with longer radials -- λ/4 or more -- for a far greater number of radials.

Since the AWG 18 wire spools I ordered contain 150 meters of wire there are exactly 5 radials on each spool. I was surprised there was no overage on the spools. When I added short tails for wrapping the ends the fifth radial came up short 50 cm. It seems when you buy 150 meters of copper these days that's exactly what you get.

The catenary is tied off a couple of meters lower than the design to avoid crossing the prop pitch motor mount. This does not effect performance or the length of the vertical wire. All it does is move the ground anchor further out away.

I swung the antenna to be SSW of the tower rather than SW. The model shows that this change increases gain towards Europe (NE) almost 1 db. However it places the antenna wires, especially the T-top wires closer to the guys. As speculated above this may have caused the change in tuning. I did make sure to model the antenna wire as insulated -- which would lower the resonant frequency, as it measures in practice -- so that is not the cause of the difference.

First try

I planted a copper ground rod where the vertical wire hangs for easy radial attachment, wrapping the radial ends around a stainless hose clamp that holds them tight to the ground rod.

After the first 4 radials were laid I measured the impedance. This brought a surprise. The radiation resistance was almost 10 Ω higher than expected. Can you see why?

Suspecting the cause I returned to the computer to play with my EZNEC model. I added a direct connection to the MININEC ground through a resistance load representing a rough guess at the impedance of the ground connection through the ground rod. Sure enough the radiation resistance rose from 24 Ω to almost 33 Ω.

The purpose of the radials is to provide a low loss return path for the near field of the antenna and to keep those fields from circulating through the lossy ground. The ground rod routes a portion of the current directly via the ground. It's self defeating.

For my final design I replaced the ground rod with a short length of ABS pipe. The radials are attached in the same way. The difference is that the radials are now isolated from ground.

Measuring again, the radiation resistance dropped to 27 Ω at resonance. This is a significant improvement. Keep in mind we are trying to improve antenna efficiency, not add so much loss that there is a direct match to 50 Ω transmission lone. As I said above, a low radiation resistance is a good thing to see. The match comes later, in this case one day later.

L network

Once I had all the radials attached and the antenna tuned as much as possible without shortening the T-top I measured the impedance at 1.830 MHz, the centre of my CW contest and DX band segment, I sat down at the computer and designed the L-network. With modern software this is trivially easy. I used TLW to do this, as I have had good success with it for other antennas.


The 31 Ω resistance is several ohms higher than at the 1.750 MHz resonant frequency. Radiation resistance tends upward above resonance. Neither is the reactance a surprise since the antenna is long at 1.830 MHz. As you can see the feed point SWR is quite high primarily due to that inductive reactance.

I chose a "low pass" style of L-network since it offers modest attenuation of harmonics which could cause problems in a multi-op or SO2R contest setup; this is handy right now since I don't yet have band pass or notch filters. Experience tells me this is tolerable for 100 watts. Another benefit is that the coil size with this style of network is usually small.

I reused the L-network from the 80 meter tower vertical I had at my Ottawa QTH. I wound a new coil from insulated AWG 14 solid copper (bought in bulk) on a scrap piece of 1" PVC pipe (~1.3" OD). The wire's insulation makes the coil diameter slightly larger than the form.

For a capacitor I used a high voltage 2,200 pf disk ceramic. All the door knob capacitors I have are no more than 500 pf and if I add them in parallel there is no room for them in the small enclosure. The ESR of the chosen capacitor is probably not very low but based on the network design the power dissipation should be low when running my rig at maximum power of 200 watts. Next year I'll revisit this, or sooner if the capacitor fails.

Notice the SWR curve above. A computer, an hour in the workshop and a trip out to the field and the SWR is perfect. No further adjustment needed for an SWR of 1.0 at 1.840 MHz and a 2.0 SWR bandwidth of 100 kHz. I displayed my confidence up front by using fixed C and L components.

On the air

I had planned to leave it be for a couple of days to haul Heliax across the field and up the tower to get the other antennas connected. Then the weather closed in with freezing drizzle making the towers unapproachable. Instead I grabbed my newly connectorized rolls of LMR400 and a couple of UHF barrel connectors and made a 260' (80 m) run directly to the shack. Cable splices were propped up on spent wooden cable reels and tightly wrapped with plastic bags for temporary weatherproofing.

In the shack the SWR remained excellent. The bandwidth improved slightly, probably due to loss in the ancient bit of RG213 I grabbed to span the last 10 meters to the feed point. Then I waited for the sun to set.

There were a couple of European contests going on and I could hear them well on the northeast Beverage. On receive the vertical is of course far noisier. Even so many of the Europeans could still be heard well on the vertical, and not very well on the 40 meter inverted vee. My initial hypothesis is that the vertical is achieving lower radiation angles that allow it to hear DX better than the noise increase would suggest.

In other directions the impact was stark. My first QSO was TO2SP in the Caribbean, who was loud on the vertical. On the northeast Beverage his signal was almost unreadable. I had a similar result with US stations who were well over S9 on the vertical and extremely attenuated on the Beverage. The second night I worked J5T and pushed through a couple of small pile ups. That bodes well.

On a few DX stations far to the south they copied my 200 watts better than I copied them. That could pose a problem. Towards Europe and the Middle East I could copy signals quite well on the Beverage while they heard me not at all. It's a combination of not having an amplifier and, perhaps, poor receiving conditions on the other end.

Need...more...Beverages. But that's a winter project, not for now when more important antenna projects beckon. For the present I am very appreciative for what I have on 160 meters.

Obstacle course

I may have to move the radials this week for the remaining work on the tower. Since the antenna is only 20 meters from the big tower and the radials are 30 meters long there are many opportunities for accidents. I know where the wires are yet I have a habit of stepping on them. Others don't have even that foreknowledge.

In any case the LMR400 runs are needed for the two runs from the shack to the 8x2 switch I've installed away from the house (more on this in a future article). I can live without the 160 meter antenna for a couple of days. It's only real purpose for the next few days is to become familiar with how it performs and identify its capabilities on the air and any grievous deficiencies.

Once I've installed the intended 200' (60 m) coax to the switch box I'll weatherproof everything and leave it be for the winter. The next few weeks will tell me whether this antenna can deliver the results I want. First up is the CQ WW CW contest and then the ARRL 160 meter contest. I have high hopes for this, my first real antenna ever for top band. There are many things you can do on 50 acres that you cannot do on a suburban lot.

Thursday, November 16, 2017

Joy of Scrounging

Hams don't scrounge as much as they once did. I knew some incredibly successful scroungers when I was young (as most of us were), and at least one who turned it into a livelihood. Back then none of us had any money and we did what we could to find good deals on used and surplus equipment, sometimes from unconventional sources that might not know what they had and the value.

That is not the case today. The same hams are far older and have little reason to scrounge. It is said that the baby boom generation is the most affluent group in all of history. Indeed, many manufacturers and dealers have sprung up to help transfer some of that wealth into their products by offering high quality and expensive products and services to cater to them (us).

Not all are so well off. Besides which there is always the pleasure of the hunt, looking for and finding an elusive part or piece of equipment for a fraction of the new price. That is, the joy of scrounging. While I'm not as well off as some I am better off than most. I can afford to buy new most of the time yet I often prefer to scrounge. Finding a great deal can be as enjoyable as running across and working a new country (DXCC) or multiplier (contest).

Talking about coax and Heliax with one of the companies I have become familiar with brought about an opportunity recently. I have been busily testing and deploying Heliax and smaller coax and control cable to connect up those antennas I am rushing to get installed before CQ WW CW next weekend. As you may know Heliax and other high quality hard line is expensive and the connectors can be worse.

I have most of what I need for this fall though not what I need next year. Worse, the connectors I have already on the used Heliax or new in the box do not necessarily have a match. For example:
  • N connectors for LDF5-50A are mostly female yet I need male on some. The reverse is true of my stock of LDF4-50A! Gender adapters are in short supply in my junk box and good quality new ones are not cheap.
  • Andrew LDF has been out of production for 10 years. The cables and connectors are becoming harder to find, whether NOS (new old stock) or used and in good condition. N connectors are especially difficult to locate on the surplus market (new ones are still available), with most of what I'm finding being DIN 7-16. Surplus UHF are very rare. DIN is nice but connects to little that hams use. DIN connectors are only useful for splicing sections of Heliax.
  • Adapters between connector types -- UHF, N, DIN, etc. -- are expensive. I have exactly one DIN 7-16 to N adapter that I found at the Dayton flea market. I also find it difficult to know or predict which I'll need and of what gender. Often when I need a particular adapter I don't have one. The alternative is to prepare a short length of coax with a suitable connector on each end.
The outcome of that conversation came several days later when I drove home with a car full of coax, Heliax and used connectors.

It was not free, but the price paid was most attractive. I had to work for some of it when handed a hacksaw to saw connectors off cable ends.

In the picture are reel ends of LMR400 (Times Microwave) and equivalent cables from other manufacturers. There are several short rolls of LDF4-50A (with connectors) and a bunch of sawn off LDF5 and LDF4 connectors. Underneath the wooden spools is a box of other odds and ends. I also paid a good price for a handful of adapters and N connectors for LMR400.

I have some work to do before these Heliax connectors can be put to use. They must be removed from the cable ends and some require cleaning. Not all may be salvagable. To my surprise I even acquired a couple of Heliax UHF connectors, that most rare of items.


Tragically the cables the connectors came from were of no use. When a transmission line in commercial service is removed from a tower and equipment buildings it is not gently handled. That takes too much time and the used cable has little value to the companies involved. It is bent, folded and mutilated as it is cut down and thrown into trailers and transported for eventual disposal. Scroungers have to be nimble to receive any consideration. Since I'm not good at this I especially appreciate what I can find.

What I can't use I will likely gift to others. Not everyone buys new so I am sure I can pass around the joy.

Saturday, November 11, 2017

Big Mast for a Big Tower

The mast for my 150' tower is designed for the class of antennas I plan to put up there. Although the antennas will be modest for this winter season there will be bigger ones in future. I don't want to redo the job later if I can avoid it.

In this article I'll step through my design and construction of a mast that suits my needs. For this tower it is more involved than popping a short pipe through a bearing into a rotator and mounting a small yagi on top.What I came up with is not ideal yet suitable to my needs. Part of the challenge was making it compatible with the prop pitch motor/rotator with its chain drive.

Pipe mating

I am fortunate to have acquired two prop pitch motors and a chain drive system custom designed for my LR20 tower. It consists of an drive unit that attaches to the outside of the tower, a matching drive shaft (lower mast) for the the chain and two bearing plates. Altogether it weighs ~200 lb (90 kg)! It is perfectly capable of handling a full size 3-element 40 meter yagi.

The lower mast is a 3.5" diameter Schedule 40 pipe (3" IPS) that sits completely inside the tower. A mast must be fitted to it. The ID of the lower mast is 3.068" which would ideally suit a 3" diameter mast nesting inside it. However these are not often stocked locally. Instead I opted for the next smaller size of Schedule 40 pipe with a diameter of 2.875" (2.5" IPS).

Since transportation is difficult I bought the pipe from someone who would deliver at a modest price; many local steel suppliers don't deliver and I don't have a suitable vehicle of my own to do it. The galvanized structural pipe I got was 24' long and 0.25" wall. At 7 lb per foot it's quite heavy!

The lower mast comes with two sets of bolt holes to mate to the antenna mast. My job was to drill mating holes in the mast, and to do it so that the mast was perfectly straight. Even a small deviation would cause the mast to jam inside the bearings when rotated.


I improvised a jig to do the machining. Before cutting the total assembly is quite long at almost 30'. Setup was difficult due to the 170' weight of the new pipe! The lower mast is on the right, complete with cog for the chain drive and sleeve to sit on the lower bearing. The ungalvanized steel parts and cuts were cleaned and painted (or repainted) to protect against rusting.

It took awhile to get both pipes parallel and the smaller pipe centred in the larger one. I used a level on top and a straight edge on the sides to achieve this. Shims were used to centre the mast on the inside. I then only had to mark the spots for drilling the mast through the existing holes on the lower mast. I had liberally applied masking tape to the mast so that I had a good surface to mark up. (Note: the LR20 tower section is a recent acquisition that I used as part of the jig. Why I have it will be covered in a future article.)

All I had to do was slide the pipes apart and drill. Putting 17/32" holes through 0.25" of cylindrical steel is not easy to do on the ground with a hand drill! There was no convenient way to use a drill press. Plenty of drilling lube kept the bit and work from burning up. Splice hardware is ½" grade 5. The holes are slightly wider than ½" to ease insertion of the bolts through the two pipes.

Finally, after weighing the options, I chose to cut the mast so that 10' (3 meters) was exposed above the top plate. Why I chose this height is discussed below.

Adapting antenna to a 3" mast

Antennas going to the top mast required some modification. The boom-to-mast clamps on most commercial antennas will not fit a 3" mast. In my case that meant some metal work on the Cushcraft XM240 40 meter yagi and Hy-Gain TH6 tri-band yagi. The XM240 was taken off the Trylon in the spring in preparation for moving to the new tower. The TH6 was last used by me over 25 years ago. Both were refurbished for this project in addition to adapting them to the 3" mast.

Modifying the TH6 was the easiest. I ordered a selection of 3" clamps from DX Engineering to replace the stock Hy-Gain clamps for the boom and boom truss. The large saddle clamps are bolted directly to the boom splice plate, eschewing the Hy-Gain mast clamp.

Four holes for the saddle clamps were drilled through the plate. I wanted to reuse two of the holes but could not because that would place the new holes too close to the existing ones and therefore weaken the plate. I was careful to ensure the boom splice bolts would not interfere with the new clamps.

The mast will now be ~1" off centre. It's still well enough balanced that I did not bother with a counterweight on one side of the boom.

The truss plate was entirely replaced by a Cycle 24 muffler style clamp. Since they proved to be more robust than expected I chose to mount the guy turnbuckles eyes directly onto the ends of the u-bolt rather than machining a plate to fit onto the u-bolt. In the spring we'll see how that works out.

I modified the (provided by the previous owner) custom boom-to-mast clamp on the Cushcraft XM240 40 meter yagi to include an integrated truss support. This is necessary since the truss will extend above the mast. The reasoning is explained in the following section.

After fitting the DX Engineering 3" saddle clamps there was enough room on the side to attach a heavy gauge length of aluminum angle. I used what was available, but a pipe is a better (stronger) choice. Since the truss support is now off centre a small amount the length of the truss cables must be adjusted to fit.

The truss is tensioned on the ground rather than on the mast. The turnbuckles are unreachable when raised to its final position. This is a common technique I've seen at several large contest stations. I liked it so I borrowed it. The mast really needs to be at least 13' (4 meters) to support a boom truss for the top yagi. However this would add additional weight that is not needed, make the mast too long for my gin pole when lifted above the pipe's centre of gravity and climbing that tall a mast to install and service the yagi is unwelcome.

The tram line to raise the antenna actually runs between the boom and truss. Indeed, as I write this the XM240 has already been trammed onto the tower this way. But that's for another article.

Bearing plate

The tower came with a blank plate that is similar to the bearing plates that support the lower mast. I used power tools to grind off unwanted bits and accumulated rust. Once the upper mast was selected I ordered a similar industrial deep-groove bearing to act as a thrust bearing at the top of the tower. The lower mast bearings are NSK while this one is by FAG. All are sealed bearings, as are the bearings in the prop pitch chain drive unit. Weather covers are not mandatory but since they can be helpful I may add those later.

Deep groove bearings of this class are quite good for amateur applications. They have excellent specs for both axial and radial loads, which is unlike too many of the mast bearing marketed to hams. However they are not adjustable. The size of bearing must be carefully selected to fit the mast. This is not difficult since it happens that metric bearing sizes have just the right dimensions to suit common pipe sizes (IPS) used in Canada and the US:
  • 1.5" nominal (1.9"/48.3 mm OD): 50 mm bore / 0.85 mm gap
  • 2.5" nominal (2.875"/73.0 mm OD): 75 mm bore / 1.0 mm gap
  • 3" nominal (3.5"/88.9 mm OD): 90 mm bore / 0.55 mm gap
Often the gap between pipe and bearing can be left as is, especially for axial loads. I plan to add a shim to the 75 mm bearing on the top plate to reduce abrasion and chatter. Done this way the load is better distributed than bearings with set screws, and there will be no screws to loosen over time. Avoid exactly matching dimensions (e.g. 3" bore for a 3" OD pipe) since fitting may be difficult or even impossible when the pipe is galvanized or is painted.


A template for placing the bearing was made in much the same way as I did previously. First I confirmed that the plate fit the tower girt, found the centre and finally overlaid a trace of the bearing and the mounting hardware, all of which are shown above left. When all was aligned I drilled ½" holes through the ¼" steel plate and test fitted the bearing. It was then removed to paint the plate; the other bearing plates are galvanized, but not this one.

The bearing plate was slipped over the upper mast on the ground and lifted as a unit. The clamp keeping it there was the same one used to assist with the mating of the two masts. I had one oversight, forgetting that the bearing plate and the gin pole could not both be in the same place at the same time!

Oops!
As a final note on the mast, I plan to add a conductive strap between the mast and tower. Although I don't intend to use this tower a 160 meter vertical (not compatible with SO2R and multi-op contesting) it will help drain static and avoid the possibility of rectification in the imperfect electrical contact via the bearings.

Raising, mating and alignment

A friend and his SUV once again provided the muscle to lift the masts. Their respective weights are approximately 75 lb and 100 lb, plus the bearing plates. The lower mast had to first be lowered into the tower so the upper bearing for the lower mast could be affixed, after which the lower mast was pulled up through the bearing and the lower plate attached. The upper mast was awkward due to its ~14' length, which even a tag line couldn't prevent from persistently catching on the top guys. This was easily resolved when I climbed the tower.


On the left you can see the clamp that stop the upper mast in the correct vertical position to drive home the bolts. The lower mast is rotated to get them aligned, assisted with tape markers on both pipes. With the clamp removed you can see that cross bolting the pipes is inadequate for keeping them concentric. The gap all around is ~3/32" (0.095").

This can only be resolved by filling the gap. When I couldn't easily locate 3/32" steel stock locally I noticed that the galvanized perforated strips I had in stock (and are found in hardware store everywhere) is 0.74" thick. That's a pretty good fit. All I had to do was cut several lengths, carefully curve them in my workshop and hook the end so they can't slide through.

On the tower I had little trouble pressing them down into the gap with the encouragement of a large wrench. Two of the shims are quite long, reaching down to the lower bolt to eliminate play at the bottom end of the upper mast. Once done and the upper bearing position tweaked the 200 lb of match spun easily in my hands. I already had the chain engaged, so the rotation included the prop pitch drive unit. The motor was added later since with it mounted the mast could only turn by powering the motor.

You may have also noticed that I replaced the splice bolts. The original 4" bolts were barely adequate to accommodate a nut and lock washer, and lock washers are not ideal for curved surfaces. The replacement bolts are 1" longer. The lock washer was replaced with a flat washer and locking is achieved with two nuts.

With that the mast was ready for the antennas to be raised.

Notes on mast strength

There seem to be two types of ham when it comes to selecting a mast: those who use whatever is at hand and those who must have the very best. A minority engineer the mast strength to the application. As to how strong a mast needs to be, well, it should as strong as it needs to be and no stronger. Not strong enough and disaster is awaiting its opportunity. Too strong adds unnecessary cost and difficulty.

I use a spreadsheet based on the ARRL mast strength calculator. The mast itself is nothing special, simply A53B grade. With my planned loads it is strong enough to survive 150 kph winds with the antennas I am mounting this winter. Next year there will be changes yet to be determined. In all likelihood I will end up with a better rating when a bigger yagi is mounted just above the top plate and a smaller yagi up top. I also have the option of substituting a larger mast.

Within reason I am not concerned about the load on the tower itself, which I know is perfectly up to the task of supporting a 3-element full size 40 meter yagi low on the mast. There is little bending moment for even a big antenna mounted close to the bearing plate, so a large diameter mast is to assure twisting strength (wind torque) and prevent slippage in the boom-to-mast clamps.

If the mast strength is not up the task -- wind load for your locale -- you have a few options:
  • Higher strength material: Although difficult or expensive to source a higher strength steel may be the best option. The yield strength of A53B class steel, the lowest and least expensive structural grade, can be doubled or tripled if you are willing to go that route.
  • Greater diameter: Increasing the pipe diameter is the superior choice in comparison to increased wall strength. Play with bending stress calculators and you'll soon discover this truth. Standard structural pipes of greater diameter are readily available almost everywhere, and are often galvanized for the pipe sizes hams would choose for masts.
  • Butting: This is a material technique to increase wall thickness where the bending moment is greatest. Butted steel tubing has been used for high-performance bicycle frames for a very long time. The special tooling makes these tubes very expensive. You can often nest the next smaller IPS pipe in a Schedule 40 pipe. For example a 2" IPS pipe (2.375" OD) slides inside a 2.5" pipe (2.875" OD; 2.469" ID) with a small gap. Dave Leeson W6NL discusses using aluminum pipes this way for antenna booms in this book Physical Design of Yagis Antennas. Since the increase in bending moment is linear the butt pipe or tube only needs to be long enough to the position on the mast where the bending moment is survivable. Unfortunately, my 2.5" pipe has 0.25" walls and I cannot slide a 2.375" OD pipe inside it. This is where you discover one difference between pipes and tubes: pipes have a seam, and that seam is not ground down on the inner surface. You can see an example of this in the earlier picture of the mated masts.
  • Antenna change: The last resort is to go with smaller antennas or lower them on the mast until the wind and ice survival objective is met. Many hams are loathe to do this even when the on-air performance difference is small.
Do whichever works for you, but be sure you do it. On the other hand, over-engineering is not only wasteful it can lead you into temptation. Putting up antennas that the mast can handle but the tower cannot is a recipe for a very ugly outcome.

A lesson

Many years ago I help to remove a tower and antenna system where the tower twisted in the wind and broke. Only the over-strength mast held it and the antennas together, preventing a ton of steel and aluminum from striking the close-packed suburban houses below! Removal required a very large crane and running interference with the extremely unhappy municipal authorities. My job was to climb the broken tower and rig the attachment between the tower and the business end of a 125' boom on a 25 tone crane.

Trust me, you never want to be in this situation. Out in a hay field a tower or mast failure may be only an expensive lesson. For most hams who live in urban and suburban settings it can be a disaster far beyond your capacity to deal with and get over.

Sunday, November 5, 2017

Patience is a Virtue

I spent part of the weekend in the ARRL Sweepstakes contest. A serious effort was not in the cards since I not only have little in the way of antennas for the moment, the contest itself has become as exciting as watching paint dry. That's a shame since back in the 1970s this contest was the focus of my contest season, since as a VE4 with a small station I lived in a DX black hole and in Sweepstakes I had an easy shot at the US eastern seaboard where my section was often in demand.

The weather was quite bad this weekend so I had an incentive to spend time in the shack, no matter my antenna situation or the antenna work waiting to be done. Rather than the contest my excitement on the bands was chasing DXpeditions. On that front I had success, working VK9CZ on 40 meters, VK9MA on 3 bands, and putting a few other DXpeditions in the log. That was fun.

My first QSO with VK9MA was very nearly scrubbed because of my impatience. Impatience drives a lot of the bad operating in pile ups, whether due to mistakes or calling out of turn. The result of my impatience was in a way humourous, as you'll see.

I had a good shot to VK9MA despite a modest yagi and no amplifier. Late afternoon the long path to VK (via Africa) on 20 meters can be quite good from eastern North America. They were pretty loud and the pile up wasn't unbearably deep or wide. The operator was turning over contacts as a steady clip, though not as fast as the best DXpedition operators.

Thus there were fewer opportunities to call, triggering my impatience. I barely listened between sending my call again and again. His pattern was predictable so that I (and everyone else) could figure out where he was listening with good accuracy. I didn't want to wait around so I tried to make every call count.

But I was too fast on the trigger. Often while calling I would stop to spin the VFO to find a quieter frequency to try my luck. This can be a good strategy. Unfortunately it can also backfire.

Spinning the VFO after a few rapid calls with no response from the DX I was horrified to hear him sending my call. Yes, horrified. Think about what I just did: I spun the VFO! Because of my impatience I was no longer on the frequency where he heard me. What to do?

Luckily I have good short term memory, a valuable attribute for a contester. I thought a moment to develop in my mind a picture of the numbers on the display when I called. He called me a second time. Desperately spinning the VFO I sent my call, hoping the frequency was close enough for him to hear me. A third time he sent my call and a report. I responded with my call again and this time added "5nn tu". With a "tu" in return the pile up resumed.

Was the "tu" merely a polite way of signalling he was giving up or did he really copy me? Luckily I showed up in their online log a few hours later when they started uploading to Club Log.

Of course it is very likely that even had I failed I would work them on that band again soon enough with their good signal and the many days left in the DXpedition. I could only laugh at myself and my poor discipline leading to unnecessary impatience. Patience truly is a virtue. Remember that should you, too, spend too much time calling and not listening in the next pile up. You'll likely get through faster with just a little patience.

Sunday, October 29, 2017

Basic Tram Line

Raising a yagi onto guyed towers requires moving them over or between guys. There are alternatives that are often impractical or expensive. These include hiring a crane or lifting the boom and elements straight up and assembling them in the air. For most hams a tram line is used since it is economical and not overly complicated. Details matter, however, since doing it wrong can cause real grief, from lost time fixing mistakes to complete loss of the antenna or injury.

Work on my big tower has been progressing apace such that I am now able to attach antennas. I have raised the first antenna and did it with a tram line. This is a side mounted yagi at ~120' (35 meters) fixed on Europe (northeast). Since time is pressing as the weather grows colder I am relying only on antenna I have on hand. Therefore I am using my Hy-Gain Explorer 14 short boom tri-bander. Next year I will switch to higher performance antennas.

I previously raised this antenna onto my 15 meter antenna in Ottawa, also using a tram. That tram had the antenna sliding up two ropes. That is impractical for my new tower. Instead I am using a more traditional tram line. I'll step through how I did it in enough detail that you could do it yourself.

In fact I did this operation entirely on my own. Since there were numerous tasks necessary to get everything working properly I did not want to call anyone out here to sit around while I fussed. When the bigger antennas are trammed to the top of the tower I will be relying on friends to help out.

Side mount bracket

The tower came with several items that were used for side mounting yagis. From these I selected what I needed to make a simple bracket suitable for this antenna. I will replace the bracket next year, but for now I saved time by using what I have on hand.

The bracket is comprised of two lengths of angle stock. One bolts directly to a tower girt while the other uses pinch clamps which allows it to be placed at any position. The weight bears on the lower bracket by means of a bolt, not the cheap muffler clamp you can see. The upper bracket holds the upper end of the pipe. A pipe substitutes for a mast to enable use of the antenna's stock boom-to-mast clamp and to allow some directional flexibility for pointing the yagi.

Tram line components

Rigging for the tram line had just been installed when the picture was taken. A large shackle anchors the aircraft cable used for the tram line itself. Below the anchor a pulley is affixed to the pipe mast. The rope is used to haul the antenna along the tram line. The cable for this operation is ~180' (55 meters) long. More than 300' (90 meters) of rope is required. Although it is possible to haul the antenna from the tower (with a shorter rope) it is far easier to do it from the ground. As a general rule every task is 3 times more difficult on the tower than on the ground.


There is a lot going on in this picture so I'll step through all of it. First I needed an anchor for the tram line. My lawn tractor was ideal: it is portable. heavy and comes with a tensioning device: reverse gear. There are three positions from which tramming can be done on a guyed tower, between each sets of guys. This area happens to be the only one without trees nearby; trees can be excellent tram line anchors. Unfortunately I had to use the treeless area to achieve the correct orientation.

Orientation is critical and requires careful planning. The position of the side mount bracket is no accident. It is the only one compatible with the bracket and pointing this particular antenna towards Europe (the antenna in the picture is oriented exactly in that direction). Notice that on this 3-element yagi the driven element is forward of the boom centre. The bracket (as we'll see) ensures that when pointed northeast the elements all stand well away from the tower.

The boom half of the mast clamp had to be reversed so that it faces the tower, for the same reason. This was easier than flipping all the elements so that the trap drain holes point down. The flat side of the clamp faces the tower, ready to be bolted onto the other half of the clamp when the antenna is lifted.

"I can fly! I can fly!"
The rope securing the boom to the tram line pulley and the haul rope must be at the antenna balance point (centre of gravity), which in this case is right where it should be: the boom-to-mast clamp. Each rope must attach at two symmetrical points either side of centre so that the antenna cannot rotate on the tram line, twist or waggle up and down.

Getting it right is very important. I fussed with it for over an hour and had to reverse the lift a few times until I had it perfect. The basic process is to do all the rope work with the antenna on the ground (supported off the ground itself), with the tram line slack. The tram line is then placed under tension, which will lift the yagi off the ground. Make sure the haul rope is tied off or the yagi will roll backward!

The ladder you see was used to inspect and adjust the ropes and pulley as the yagi first lifted off the ground. The elements are pointed slightly upward to assist with clearing the guys immediately below the bracket. A tag line is attached to the boom so that the elements can be steered around the tower and guys, if necessary.

The tractor made this stage of the operation easy to repeat several times as I fixed problems with the rigging. Remember to chock the wheels when the tension is set!

Raising the antenna

Hauling the antenna up the tower is perhaps the easiest task. Setup takes the most time, and is well worth the investment of time and efforts. Should the antenna spin out of the correct orientation while hauling I strongly recommend immediately lowering it and fixing the problem. It's far easier to correct problems on the ground than while the yagi is dangling 30 meters in midair.

The Explorer 14 weighs only 45 lb (20 kg). Hauling the antenna up the tram line by hand is quite easy. It is made easier by the mechanical advantage the tram line affords. This is because the antenna is travelling up a slope rather than straight up. The trade off is a longer hauling distance. I attached a rope cleat to the bottom of the tower so that I could rest during the haul and to secure the antenna while working on it on the ground or in its final position.

In the next picture the antenna is beginning to straddle the tower. I didn't even need to use the tag line to achieve this perfect orientation. After all the trouble with the setup the antenna raising proceeded beautifully. If you are not so lucky do take the time to ensure the elements each go where they should. If the tag line in insufficient do it from the tower. Yagi element tips are fragile! This is where having a friend along to assist is very welcome.

What you can't see in the picture is the wind blowing. The wind was 20 to 30 kph perpendicular to the tram line, with gusts up to 50 kph above the tree tops. It wasn't a factor. Although I was concerned about the wind there was a storm coming in followed by a forecast of several days rain. So I went ahead. When the tram is properly rigged a stiff breeze is not a serious difficulty.

Attaching the yagi

Once the haul rope bottoms out on the pulley the hauling is done. Done properly the boom-to-mast clamp will rest very close to its intended position. Before climbing the tower the tram line should be made slack. When you do this the haul rope will relax and allow the antenna to rest against the mast. Bolting on the yagi is made easier when the tram line and pulley don't offer resistance. The vertical position of the yagi can be adjusted after it is clamped on and the tram line system is detached. Don't delay climbing the tower when the tram line is slack since the antenna has more freedom to move in the wind.

In the adjacent picture the yagi has just been bolted to the bracket mast and the tag line (green) and haul rope (white) removed from the antenna and tied off.

The picture shows detail that was missing in earlier pictures. There are a few items to note.

I used the boom half of the clamp to achieve the two symmetrical tie off points for the haul rope and tram line cradle.

There are two shackles connecting the cradle to the pulley. With just one shackle the yagi would twist to one side.

To slip the pulley on and off the tram line I used one with a removable wheel (sheave). To get it off the tram line I knock out the axle retaining clip, remove the axle and then separate the wheel from the body. It goes back together the same way. This is quick and easy compared to detaching the cable anchors to slide the pulley off the end of the cable.

Epilogue

I did not take an antenna analyzer up with me. With the conductive tram line present I would not have gotten good impedance measurements. I'll do that the next time I'm on the tower. I don't anticipate any problem. My modelling of guy interactions with respect to the orientation of this antenna promises no difficulties. We'll have to see if that is indeed the case.

The bottom of the tram line was tied off at the tower but left anchored at 120'. It will next be raised to the very top to raise larger yagis to the rotating mast. This small lift was good practice.

The antenna was raised on the Saturday of the CQ WW SSB contest. The weather was about to turn ugly and I was in any case unable to effectively compete due to my temporary lack of good antennas during construction. I expect to do better when the CW contest rolls around in several weeks.

Monday, October 23, 2017

Pile ups: 3 Basic Methods for Getting Heard

In my previous article I mentioned putting up my old multi-band inverted vee as an interim measure to get me on 17, 30 and 40 meters while the big tower project is ongoing. My immediate goal was 3C0L. I did work them on several bands though not as many as I'd wish since I gave priority to tower and antenna work while the weather continued to be pleasant.

In the process of cracking the pile ups on 3C0L and others I thought it interesting that I was using 3 distinct operating techniques depending on the pile-up depth, propagation and the competitiveness of my signal. They can be used by anyone, from little pistol to big gun, and they are used.

The purpose of this article is not so much to reveal anything novel other than to categorize them in a way that can help the DXer choose how to approach each pile up. If you've followed this blog for awhile you'll know that in my QRP years I wrote several articles on cracking pile ups with a tiny signal. It seems worthwhile to add this one to complement what I've written earlier.

#1: Predict where the DX is listening

This is the most common technique and is widely understood and practiced. There is no need for me to repeat here what everyone knows. If you use it you'll know that sometimes it works well and other times not at all. The difference in results often comes down to whether your signal is competitive with others in the pile up.

Competitiveness is not only about antenna and power. With the best station in the world you will be beat out if propagation favours another region of the world. For us in eastern North American that is most often Europe. For example, with a low solar flux north-south paths are better on the high bands. That puts North America at a disadvantage compared to Europe for working 3C0L. Even small stations in Europe will outgun you.

However if you are competitive in the pile up and you are good at predicting the DX operator's pattern you will soon have the QSO in the log. Prediction works well much of the time.

#2: Call where others are not

When you are not competitive your skill at predicting where the DX is listening will most often lead to frustration. Many others can predict as well as you and your signal will be underneath theirs. You'll end up frustrated as you fail to be heard. Those with little signals know this feeling all too well; it's a part of the game. Another strategy is required.

In the past 24 hours I used the following technique twice: to call where others are not. The first case was 3C0L on SSB. They chose to work stations by numbers. I'm too busy to sit near the rig to wait for them to call for 3's so I kept missing an opportunity to call. When I was able to call the pile up was huge and in the few minutes they worked 3's I was unsuccessful.

Catching them one last time on 20 meters before they shut down (14.190 MHz, and listening up 5 to 10 kHz) I did the prediction thing for a couple of calls before realizing this was unlikely to work in the few minutes remaining. So I listened to learn where others were calling. The vast bulk of the callers were on 14.195 MHz, the frequency of the previous QSO -- there are lots of predictors out there! There were a several callers on 14.200 MHz and only a few in between.

I picked 14.1975, right in the middle of the pile up range, and made my call. No one else was heard on that frequency. It took 2 or 3 calls until he QSY'd and found me. Into the log he went. The mass of predictors then made their call on my frequency.

The second example was FT5WQ/MM on 40 meters CW. This is not a country, just an opportunity to practice pile up technique. With the inverted vee rather than a yagi, and no amplifier, I was not competitive for the size of pile up. Prediction didn't work for me. So I delayed a second when he solicited callers and tuned the VFO to where I heard silence. Again, it took 2 calls to put him in the log.

This technique works because even the most dedicated DXpeditioner gets fatigued from constantly trying to pick a call sign out of dozens or hundreds of overlaid signals. Eventually they make an unpredictable turn of the VFO to avoid the predictors. When that happens they'll usually stop at the first isolated signal they find. That signal can be yours.

#3: Uh oh, where's the pile up?

The first two techniques can be succinctly stated as calling where he's listening and calling where others are not transmitting, respectively. But what if you can't hear the pile up at all? This happened to me with 3C0L on 10 meters CW. He was working mostly Europe and a few in North and South America. Evening was crossing Europe and the propagation gradually favoured this hemisphere.

From VE3 I heard not a whiff on any of them, not in Europe and not in the Americas. Prediction was impossible. I didn't know where he was listening or where others were transmitting. This is a dilemma. This brings us to the final technique: to call blind and hope for the best.

Despite the lack of signals there was one source of information, marginally useful though it was: the DX spotting network. Occasionally the DX will be spotted with the frequency where he was worked. I saw one of these timestamped a few minutes earlier. That makes the information old. Yet it was all I had to go on. That one said listening up 3 so I called up 2.5 kHz.

Despite calling blind I actually got through within a few minutes. I was monitoring the spots and would have tried a new offset if someone mentioned one, but no one did and I stayed where I was. I returned the favour by spotting my offset to work him.

Although a poor strategy in most cases don't hesitate to use it when all else fails.