One of the first and probably the only ham radio related job I did this summer was to refurbish the 80/160 dual band ground plane antenna. Six weeks later and I can’t remember why on earth I replaced a working antenna. My DRAM will refresh itself as I type this.
When I had my tower installed ten years ago, I was so glad to finally hear and work things above 10MHz that I didn’t bother for the low bands. I had a decent short loaded vertical dipole antenna for 40 so I only missed the fun on 160 and 80. Fun? Who cares about those hard noisy bands? But then I wanted to take the contesting experience to the next level. So I needed to get active on the low bands. An inverted V on 80 with the apex as high as the tower was cranked up. That kinda worked. Everything works when you’re starting out on a band. For 160 I used whatever wire I could squeeze in and fed it with the SG-230 autotuner. Then came QRO and I needed a solution without the 200W max black magic box. Black magic or black box?
Early in 2006 ON4AFU offered me a 80/160 trap with RG-58. He didn’t use it anymore. I think I worked my first US on Top Band with that. Nope, I just checked and my first Whiskey on 160 was K1RX in the ARRL DX CW 2005. On 3830 for this contest I said about the low bands: ‘an inverted L with some radials fed with a SGC-230 coupler for 80/160m.’ There you go. I left the inverted V path earlier than I remembered.
The trapped vertical was a bit of an odd creation. I used my old trusty aluminium push up mast to get to a height of 10 or 11 meter. The rest was horizontal making it a trapped inverted L. I think the radials were laid out temporarily on the ground during the contest. I got away with that because there were no kids yet. Anyway that flimsy trap thing soon broke and I needed to find a solution. I was determined to go vertical on 80. One thing I learned the hard way was that I could not put up two low dipoles for 160 and 80 on the same pulley on the tower. They interacted like hell. Putting these up at right angles was out of the question because the garden is too small. As long as I was running 100W the smarttuner would turn things to 50 ohm on both 80 and 160. So making a vertical for 80 that did not need to use the tower for suspension would free that resource for a 160 dipole. But first things first. Let’s get vertical on 3.5 MHz.
I adapted the trapped inverted L design. First I need to get as high as possible. The aluminium push up mast only takes me to 10m. I had salvaged a piece of the famous DK9SQ fibre glass poles. To combine these I had a Ertalon (nylon?) coupling piece made on the lathe that went into the upper aluminium tube and where the fibre glass section would slide over on the other end of the coupling piece. That took me to 16m. The rest was floating horizontally to a pole on the edge of the garden, making it effectively an inverted L. Now for the radials. The temporary ‘just throw ‘m on the ground’ configuration would most certainly result in an XYL no-no. Which is only normal. I initially sold this as experimental to get spousal approval. So for the first time I made use of elevated radials. I calculated the length of a 80m dipole, and put these two legs in the hedge that borders my garden. That is roughly two and a half meter high. Then I adjusted the L wire until resonance. I had never used such a good antenna on 80. It rocked. I really worked great. So good that my QRO made me an alligator on 80. A problem that still persists to this day.
But this behemoth was a pain to put up. Sometimes literally painful. Squeezed fingers and a sore arm. The fibre glass pole, the L wire and the seven aluminium push up sections. The combined weight! It needed to be pushed up by hand. One hand would hold the bottom section while the other hand would slide out the next section. Then the upper part needed to be held steady while the first hand tightened the collar to hold two sections together. Repeat six times. The higher it gets, the heavier it becomes. All this while standing on a small ladder because the lower tube is two meter long. Really a pain. And when it’s windy and the sections are waving in the wind, the aluminium sections would jam because they would get slightly bent. Yanking it sometimes made the upper section slide back down. Sometimes then the collar would smash my thumb of the hand that held the lower section in place. I can assure you that doing this only was worth the while because it was such a great antenna and because us contesters are just plain nuts. Anyway I used this for a couple of years and worked many real DX on it.
To complete the antenna farm, I bought a set of loading coils for 160 and converted the old 80m inverted V. SWR 2:1 bandwidth was just right to cover most of the DX action. That again was a huge improvement and once again the DXCC counter incremented every contest. I could even do SO2R on both low bands now!
But not only the contest part of the QTH improved. We did a lot of changes and in summer 2009 we would complete the biggest project so far. That is: remove all old cracked concrete the previous owners had poured and dubbed the terrace. It looked like a scale model to demonstrate plate tectonics. We removed six (!) truckloads of reinforced concrete and made a flat and levelled terrace with modern concrete tiles. That summer we also had the roof and the overhang totally redone. In a trendy colour nonetheless. Out with the old, in with the new. Quite a costly endeavour but I’m proud to say the makeover made our house look more modern and less shabby.
Without the XYL even mentioning a word about it, I decided that my new terrace and garden look would not be desecrated with a bulky galvanized support that had moss covered concrete blocks as a base, and a bunch of aluminium tubing and fiber glass fishing poles. That had to go. Yet I did not want to give up the 80m GP antenna with two elevated radials. This thing was just too good. Since the new terrace and ground levelling around it involved redoing a part of the lawn, I decided to use the best of both worlds. That is: have the inverted L with elevated radials. But use the big crank up tower as a suspension point. That would mean that when the tower is all the way up, it would be almost a vertical full size on 3.5MHz. I put a nice thick wooden pole in a corner of the lawn. It’s 10 cm in diameter and sits almost a meter deep anchored in quick cement. The pole blends in with the terrace, the hedge and the scenery. The top is about two and a half meter high, maybe three. That’s where the elevated radials connect to the feed point and the 80m wire goes up.
It was so much easier to pull up a rope to raise the antenna wire to the top of the tower where there is a pulley. No more pushing weights with the aluminium sections. No more strained muscles or smashed finger nails. Also the tower does not swing in the wind. If the wind were so hard it would made the tower swing, I wouldn’t crank it up in the first place. The fibre pole did swing even in a gentle breeze. While swinging the antenna wire would sometimes touch the conducting aluminium sections and cause the amp to trip and the wire’s insulation to melt. One Monday my neighbour asked me why he had seen sparks high up on my antennas the nights before. Later on I made an assembly to prevent that and keep the wire away from the aluminium pole but it only added extra weight to lift. But not anymore!
Somewhere along I bought the notorious MFJ-998. The plan was to use the 80m antenna, lengthen it somewhere halfway between 80 and 160 and use this QRO tuner to get the wire working on these two bands. I tried many things while running this experiment and anxiously altered many parameters in this antenna system to get it all working. I did so many things that I forgot most. What I did try was adding tons of ferrite at the feed point and much more elevated radials. So from the wooden pole there were a dozen of wires between 20m and 50m long running to all corners of the garden. High enough to walk under at all times. This was a bit of a pain as all these radials were always in the way when holding or throwing something in the air. Like a Frisbee. Or a ladder. Every year I needed to get them out of the way to trim the hedge to put them back up afterwards. And of course each and every time someone came to visit us, the same old joke got told: the XYL’s laundry must dry pretty fast with all these clotheslines. Hilarious.
I had so much faith in the electronics of the QRO tuner placed remotely in a cabinet at the feed point and really believed this would solve all my problems. But it never worked as a whole and I retired the QRO autotuner. After so many years and doing so many things, I forgot the details. In the end I seem to remember it turned out to be a water soaked coax at the feed point. Stupid me never checked that and trusted the part of the system that was used and that had been working fine before. But the extra radials stayed and I decided that resonance or at least ‘native 50 ohm’ was the way to go. I’d to the smart tuning from now on.
What if I could ‘dualize’ this proven single band 80m concept for 160 combined with 80? I could parallel a second wire for 160. I would need a second pulley for the 160 wire. I would need to find a way to shorten the 160m L because the garden is not wide enough. I put a second arm with pulley on the top of the tower. I folded the ends of the 160 L back along the wire that came from the tower, making it linear loaded. Used 50cm lengths of electric conduit as spacers. I made a plastic spacer strip to keep both wires apart at the common feed point. In the end it was a crazy system: lots of wires floating above our heads. I had a hard time trying to explain to non-ham visitors that they are not clotheslines. Apart from these there was also the two wires going up the tower, one so long that it had to be folded back. Two pulleys and also two ropes to pull up the wires. Crazy but it worked. It worked well. The only two tradeoffs were sacrificing SO2R on 80/160 as the antennas shared a common coax, and the whole circus of taking the radials out of the trees and putting them back in after the yearly round of shaving the hedge.
Along the way I had made a temporary experimental feed point assembly. But as it happens here at ON5ZO’s, temporary often becomes permanent. Another important factor here is the field day character. For each contest I need to crank up the tower and hoist the low band wires up in the air. But many contests don’t have 160. So why add another load to the tower, why risk another copper wire spaghetti when the band isn’t used in the contest I’m about to enter? I could just leave it coiled up under the wooden pole. But since the end of the wire is still connected to the feed point, this messes up the 80m operation. So I need to disconnect the 160 terminal from the feed point. Each and every contest. Standing on a ladder. First both wire terminals shared a common bolt. Removing 160 would mean the 80 terminal jumped away and needed to be put on again. Where did that washer go? Where did the nut fall? Later on I gave each wire a dedicated bolt. Using a wing nut for the 160 cable shoe so I didn’t need a wrench anymore. All very complex isn’t it? A fixed setup would be so much easier. Just flip the switch, put butt in chair and call CQ TEST. No more field day style. No more wire and rope spaghetti. But better this than no tower at all.
So the plan for this summer was:
- See if there is a way to return to two sets of resonant radials.
- Make a more beefy feed point assembly. Although my quick ‘n dirty temporary fix was already OK.
- Provide extra choking with off the shelf QRO balun.
- Make adding/removing the 160 wire easier.
- Do something about the pigeons and especially their excrements; pole = no go zone for birds.
- Test extensively in the three major contests (IARU, EUHFC and WAECW).
Plan executed as in the picture. The radials for 160 need to be bent.
I put a temporary dipole centre piece on the pole. Cut two lengths of wire to form a dipole for 3535 resonance. Theory says these will need to be shorter if they’re close to the ground. Shiver me timbers! I had to cut them way shorter for the antenna analyser to show resonance on the desired frequency. But I achieved resonance. Then add the next set for 160. Again I had to cut a big deal off. I didn’t take notes and seven weeks is too long ago but I think it was 70% of the normal theoretical length or even shorter. Radials are between two and three meters high. For 160 I achieved a dip around 1835 but not really a low SWR. And the second set of radials (160) did not affect the first pair’s (80) resonance.
I did a quick test with the tower raised. The WX was superb. Of course, no where near a contest. The length of the old wire for 80 was still spot on and the antenna analyser showed a perfect dip around the desired frequency. The SWR graph and X and Z values were about the same across the CW portion as in the old setup so it should work.
For 160 the wire was too short now. My initial plan was to lengthen the linear loading at the end of the L. But then I needed to alter the loading assembly I made. Why not just cut the vertical wire and add some extra there? I think I added a good two meter of wire. I used one of the handy dandy gimmicks found plenty @ON5ZO: a piece of plexi (acrylic) strip, 4 cm by 20 cm or so with four holes sized the diameter of the antenna wire. I use these as end insulators, parallel dipole spreaders and now also as cable splices. The cable goes through one hole over the other side back into the other hole and makes a strain relief that doesn’t let loose and doesn’t harm the insulation. The strip itself never breaks, never bends and is weather resistant. Just don’t cut it with an angle grinder with a thin cutting disk. The stuff melts into a blob. The hacksaw is the way to go. Better is the sheet metal cutting press if you have access.
To join the wires I used some electric cable splice connectors. The manufacturer did a demo at work a few months ago and I got a few free samples. I bet the sales rep will never think of this application for his product. Unless he is a ham. The splice itself and the connecting block is covered with quite a few layers of electrical tape around the plexi strip.
I had now achieved resonance on both 80 and 160. The SWR curve was what was to be expected. Less broad on 160 than before so I assume this means less losses? I just maintain a simple blog and don’t write low band antenna books so I’m not an expert. Fact is that this is the best I can do for Top Band and it is what it is. If it’s as good as the previous version, I’m happy. If better then I’m happier. If worse then I can always go back to the ‘many radials of random length’ setup.
Feed point assembly
I decided to add extra choking. There is already a huge amount of ferrite cores over the coax at the feed point terminal. A few years ago, when I had problems getting the system to work, I had Peter of DX-wire.de make me a ridiculously long custom Teflon coax choke with tons of ferrites. But I wanted more. Since spare time is scarce I have to make choices. So no homebrew balun. A few years ago I traded my dollar bills for a BalunDesigns.com choke. Great stuff but this time I didn’t want to spend more on shipping and custom duties than what the actual balun costs. So I decided to buy a ON7FU balun. If ON4HIL / OT2A is happy with ON7FU stuff, I probably will be too.
The balun is one thing, but I wanted the wires not to connect directly to the balun case for mechanical stability. And I needed to observe the 160-quick-disconnect rule. So I connected the radials to a 5 mm thick aluminum angle stock. And the 80/160 wires to another. Both were joined with a piece of kitchen cutting board plastic. The hot and cold terminals so to speak were connected to both aluminum angle profiles by means of 20 mm wide aluminum strips. I could have used a wire but this looked nicer. I don’t know if low inductance connections matter at these low frequencies? But this will probably be low inductance. All nuts and bolts are stainless and on each connection the proverbial liberal amount of Penetrox is used.
I used two bolts, one for 80 and one for 160. If I want to disconnect the 160 wire, I only have to loosen one nut. I used a second counter nut on the 80 terminal as this one is not supposed to get disconnected. For strain relied as the wire is pulled up towards the top of the mast, I simply turn the wires two times through the cutout hole that is the top of the cutting board. This way the 160 wire comes off in a breeze too. I had to perform this action between EUHFC which includes 160 and WAE which is without Top Band. I just need the ladder and a wrench size 10. It takes only a few minutes. With the recent garden makeover the ground there is levelled and compacted so the ladder doesn’t sink in the soil anymore. Added bonus for the field day style antenna czar.
Stop that pigeon! Yankee Doodle Pigeon likes my big wooden pole. Result: a layer of excrements on the antenna feed point and on the ground. Trees enough. Even overhead electrical lines. Go sh!t there pigeons! So I added a little extra and since then I haven’t seen a single pigeon landing on my pole.
The last part of the plan has proven a bit problematic. So far I used the antenna in the IARU and EUHFC contests. I can’t tell if the antenna worked, and what’s more if it outperformed my old setup. Or not? Low band conditions were poor. QRN, static and noise were omnipresent in full force. And it’s not the time of the year for low band operations. Using it in WAE could have told me something more. That’s a DX only contest and I’ve come to know what (not) to expect in this contest during August summer doldrums. But as you might know my participation in this one was limited to 100 Q on twenty and fifteen meters. So I’ll have to wait until the contests in October for less summer QRN. Maybe that’ll tell me something more.
While I was at it, I made a solution for a problem. I hope a picture really tells more than a thousand words.
Picture above. Now the thousand words.
So on top of the tower there is an arm with a pulley. That pulley is used to hoist another pulley (small auxiliary pulley) with a rope. Why the aux pulley and not just pull of the L wire itself? Because ON5ZO is not a ‘set and forget’ station. Each contest means putting the whole shebang back up. No matter how you attach that wire to the rope on a crank up tower, it’s always going to get stuck somewhere and jam. Maybe the vertical part of the L is too long and slack wire needs to be pulled to the horizontal side? Or vice versa. But with the second pulley to guide the antenna wire, it can just slide along in all directions you want to pull it. That works just fine.
But cranking the tower up and down means the lifting rope gets twisted around its own axis as you coil the rope up to keep it nicely waiting for the next contest. And when I pull the auxiliary pulley up, the rope untwists itself again by turning the other way round. This means that the aux pulley also twists around its own axis. And this movement in turn tangles up the blue L wire. When it’s tangled up around the pulley, it can no longer slide freely in either direction. That means I need to lower the pulley, straighten the antenna wire and repeat until it works. The first time the auxiliary pulley jammed and I didn’t know why. You can’t see the wire coiling up twenty one meters high. Maybe I should hop on the drone bandwagon and film my stuff in the air? After a dozen times I more or less know how to handle it to minimize the effect. But it would be nice to have a way to just lift the pulley by pulling the rope and not having to worry about the wire tangling up.
Maybe by now you understand a little better that ‘setting up for the contest’ for me really is a matter of keeping an eye on many things each and every contest weekend. Long live the ARRL 10m contest! No low band wires needed.
The solution of course is to make sure that the aux pulley does not rotate when the rope that hoists it rotates. I did this (see picture) with two eye bolts and a scrap piece of Ertalon. I didn’t even care to debur it. The picture shows the auxiliary pulley which carries the 160m L wire. The new drill press I recently bought made it easy to drill a hole straight through. The bolt with the hook is tightened against the white block. The other eyebolt can turn freely in the plastic block. This gets attached to the hoisting rope. When this rope (un)twists, the bolt turns idle in the plastic block but the bolt holding the pulley for the wire doesn’t rotate. So the wire doesn’t get coiled up anymore. Used three times already (test + IARU + EUHFC) and it really is a perfect solution to a problem that has bothered me quite a lot.
Note: I know that there are small pulleys with an eye that rotates 360° relative to the pulley’s wheel. You can just buy these. Heck I have one or two of these in use somewhere on the auxiliary poles and towers that hold the ends of the low band wires. But I just wanted to use the pulley I had in stock.
Congratulations if you made it to the end of this text and read it all. Even if diagonally. 73!