ARROW Communications Association

The Summer passed, and I never got around to building the fan vertical I described in episode 11. The 40/80 fan dipole languishes, coiled up in a box in the basement. I keep thinking about putting it up, and may yet ... perhaps as an NVIS antenna. But I still wasn't satisfied!

I kept reading and studying on line and off, at places like www.cebik.com, among many others. I thought hard about making a 2 element wire quad for 40m, to try to get some gain (an extra S-unit would be a big help to my QRP station). Finally, though, I decided on a vertical delta loop, fed at the center of the bottom side with ladder line. I would orient it so it favored the directions that were disfavored by the 20/40/80m fan dipole, so they would compliment each other (on 40m, at least).

I got out my huge spool of 18 gauge magnet wire and determined to make my own 600 ohm ladder line. The low loss should allow broad banded operation of the loop using my Z-11 autotuner. I got out the old broken green plastic deck chair and the jig saw, and cut out about fifty 5-6" X 1/2" pieces. Then I used my soldering iron to melt a hole in each end of each spreader piece.

I mulled over various construction methods. I knew this was going to be time consuming, and, with my usual enthusiasm for a new antenna, I didn't want to spend any more time than necessary building it. I read up on other people's construction methods, but finally decided to get creative and try my own idea - to thread the wires through the holes in the spacers and then glue or clamp it in place somehow. I decided to use sheet metal screws to bind the wire into the holes in the plastic spacers, and bought a box of #6 x 1/2" screws.

I spent probably 3-4 hours watching a football game and assembling that ladder line. It was tedious and a bit frustrating. Threading the spacers onto the wires was a pain, as my holes were neither precisely aligned nor particularly uniform in size. Fixing the spacers to the wire with the screws was clumsy and time consuming, too, and I worried I would weaken the wire where the threads of the screws cut into it. Finally I had it done, and a couple of days later went out to try to assemble the mess -- it was becoming a mess because the ladder line spacer ends kept snagging on the wire, and it was in danger of becoming a snarled rats-nest of copper and plastic.

I successfully got it spread out into the woods, though. I measured out the delta loop and tied the apex to a rope I had already strung through a tree branch possibly at 70 or 80 feet, and pulled it up. The thin wire kept snagging on low branches, smaller trees, and tall bushes. What a pain it was putting it up.

At one point I pulled on the rope to lift the loop a little higher, and somehow the knot I had used to hold the wire came untied. Unfortunately, that was also the knot that tied the ends of the rope together in a big loop ... so suddenly I was holding one end of the rope and the other end was hanging, disconnected, 30 or 40 feet in the air. The light was fading as I did the only thing I could do - pull the rope completely down from the tree, get the fishing rod, and try to get the sinker over that same branch or a similar one nearby.

Fortunately I was successful pretty quickly, and got the rope back in place. I got the loop back up and stretched the two lower corners out with some yellow construction marker line to a couple of the small trees. Now the bottom wire was about 8' off the ground - high enough for the deer (and me) to not run into it, but not so high as to lose some of the ground effect benefits I hoped the loop would enjoy. (See the Cebik articles on SCVs - self-contained verticals, to understand this.)

With the loop now in place, I strung out the ladder line and attached it to the ends of the loop with a couple of wire nuts (they work, and avoid the crumbling solder I saw on my fan dipole's feedpoint after less than a year in the elements). I screwed a couple of TV antenna wire standoffs, as high as I could reach, into a few trees leading in the direction of the house, and used them to hang the ladder line out of harm's way.

Then the ladder line broke, right at one of the spreader-screws - just what I had feared. With less ladder line than I wanted, I now had to cover a distance of about 25-30 feet down the side of the house and into the shack. Dark was closing in fast as I placed a coaxial balun (15 turns of RG-58 taped around a plastic soft drink bottle) at the end of the ladder line, and ran the RG-58 along the house and into the shack cable entrance.

I connected the MFJ-259b to the coax first, and it resonated poorly (4 or 5:1 SWR) at about 11 and 22 mHz. I wasn't sure what I would be seeing, but I decided to hook up the tuner and see what it could do. I searched and searched the shack, but was unable to find the autotuner. I did, however, find an old MFJ-941a tuner, to which I attached the coax. I fired up the rig and tried to adjust the tuner, but I might as well have flushed a wire down the basement toilet for an antenna - it was as deaf as a post. No amount of fiddling with the tuner seemed to make much of a difference.

I fussed with the tuner for an hour, expecting to get some kind of decent results on 40 and 15 meters, but performance was as if there was no antenna there at all. I couldn't achieve an SWR much below 6:1 anywhere, and it acted odd, dipping for just a second to as low as 4:1 and then bouncing back up, up, up. I wondered if the tuner was in working order, but I also remembered the work I did replacing the band switch on it some years ago. I know the beast pretty well, and there really isn't much in it that CAN go wrong. I suspected that the coax was just too long and lossy at the high SWR values in question.

Just in case something had broken, the next afternoon I went out and inspected the whole setup from stem to stern, but it was just as it should be. I re-tested it with the rig, and it was still totally deaf. I went outside and fussed with it a bit, and ... another break occurred in the ladder line. This was no good. With all the movement those trees were going to see during the Winter windstorms, this setup wouldn't last five minutes.

So I ran to Radio Shack for some TV twin lead - that would provide a much more durable low-loss feedline. They don't carry it any more, they said, and they directed me to the best local "we've got just about everything" hardware store. The hardware guys said "nope", as they no longer carry 300 ohm twinlead either. I went to the TV repair shop next door to the hardware, but the gentlemen there (both looked to be approaching 80, or past it) said they had none. So I went to the big box builder's supply place, but they don't carry such ancient stuff any more either.

With the first big contest of the Fall season just a day away, I was getting desperate. I remembered my first horizontal loop, and how well it worked with just clear-jacketed speaker wire for feedline. It IS parallel feedline, after all, and has a characteristic impedance around 90-100 Ohms - almost a perfect match for a loop at resonance. But the big box store had only 250' spools, and I knew I'd never use that much of the stuff in a lifetime. Plus, I was still feeling frugal, and spending the sale-priced $50+tax for the spool was just more than I could stomach right then. So I went home empty handed, determined to find some twin lead or, as last resort, maybe return the next day for the speaker wire (or see if K-Mart or someplace had a hundred feet or so in their car stereo section).

The next day I called a half dozen TV repairs, and one of them said they had some. Interestingly, this turned out to be the place I had visited the day before. They had taken over the business of a competitor some years ago and still maintained both names and phone numbers. This time the gentleman said the DID have some twinlead, and that his brother probably just didn't know where it was when I asked the day before. So after work I stopped back there and paid over $25 for what might be the very last roll of 300 Ohm twin lead in the whole county. It was labeled 100', but seemed a bit disarranged, so I suspected it might not be that long, but I was too desperate to care.

I dashed home, cut down the hand-made ladder line. What a waste of time and materials - I should have used wire from my big spool of 14 ga. solid THNN house wire - you can swing from the trees on that stuff - and attached it to the spreaders with small wire ties and a drop of superglue under each one, as described by others on the web.

Anyway, I strung up the TV twin lead in place of the ladder line and threaded the end into the shack along with the other cables (a possible source of meaningful loss, I noted, being so close to the other feedlines for a foot or two).

I took the MFJ analyzer into the woods, put it on a step ladder at the feedpoint of the loop, and checked the SWR before connecting it to the feedline. It had dips to 3.3:1 SWR around 6.7 mHz and 20 mHz. I knew that, with a characteristic impedance of 100 Ohms or more, I would never see less than a 2:1 SWR on my 50 Ohm MFJ-259 analyzer. I lopped off a half dozen pieces of wire to shorten the loop, checking with the analyzer each time, until I got the lowest SWR points inside the 40 and 15m bands. Then I connected the twin lead to the loop with a couple of very small wire nuts, and sprayed the connection down with several coats of clear coat spray, hoping to offset any weathering over Winter.

Back in the shack, the analyzer measured pretty much the same values, though the resonance seemed to have shifted a bit higher (probably some effect of the feedline being too near and parallel to the bottom horizontal section of the delta loop). The low SWR points were a bit above the bands, but it was broad enough to contain the 40m and 15m bands well under 4:1, which was fine.

I rousted around in the shack and FINALLY found my Z-11 autotuner. I soldered a PL-259 on the end of the twin lead (yeah, I know that's not optimal, and I should have used a balun outside with a short length of coax into the shack, but ... what the heck.).

I got the tuner and rig connected and powered up, and ... the loop now SOUNDED like a real antenna, with lots of atmospheric noise and a few signals popping up right off the bat. I scanned around, switching between the loop and the fan dipole, and the loop was only sometimes equal, and usually an S-unit or so worse. The tuner matched the loop just fine, though, so with the rig on 5 watts as usual I called EM5U, who was operating contest-style (working them as fast as he could) at the bottom of 40m. He heard me the first call! I had to repeat my callsign a half dozen times after that, but he gave me a "599" and moved on to his next contact.

Then I heard a weaker signal calling CQ around 7028 kHz, and the loop was at least equal to the fan for this one. It was AA1TJ, Mike, in Roxbury, Vermont, and I answered his CQ. Mike was running a homebrew transmitter with 670 mW into an end fed wire, and using a homebrew, single tube (6AK5, he said) receiver. Mike and I had a nice leisurely QSO for about 15 minutes, just at sundown. (Note that the bands tend to change more quickly at sun-up and sundown.)

At first the loop was even better than the 20/40/80m fan dipole/inverted vee, which is up about 60 or 70 feet at the apex. The fan is my best antenna except for off the ends or in the direction of a couple of nulls, when the verticals tend to barely beat it (though they are usually 1-2 S-units down from it the rest of the time). After about ten minutes Mike started to QSB down on the loop, and I was able to switch to the fan and bring him back up to S6+. I'm sure that was because propagation conditions were changing, and the best angle of radiation was probably rising or falling. Before we said 73 and closed, Mike had peaked on the inverted vee at S7+, and I could barely hear him on the loop. QSB was very strong on either antenna. It was a great QSO, though, and it was clear that ... the loop works! (In a nice email he sent later, Mike said the loop "must be tuned like a Stradivarius".)

So now I have 4 antennas: the 20/40/80/(& 15) meter dipole at 60-70 feet with ends at about 25', the HF9v vertical with about 14 radials, the 10/15/20 vertical dipole swinging about 50' up in the trees (coax fed), and the new 40m full wave vertical delta loop fed with TV twinlead. I am just about ready for a killer CW Sweepstakes, when, this weekend, I hope to complete my first QRP clean sweep.

Last year I got 79 of 80 sections (I amazed myself!) and scored 4th place QRP in the Great Lakes division, and I am hot to do better this time. Besides, I "know" those other top QRP ops have towers, beams, and other directional antennas with GAIN. If I can run with them with just my wires and verticals - I feel like I've won anyway. And if I ever get a directional antenna system ... watch out -- I'll kick butt!!

I mentioned this to my extremely-supportive wife, and she has asked several times since then just what kind of directional antenna system I would want ... maybe I'll get that StepIR beam on a roof tower someday after all! But, for this contest season I'm in pretty good shape.

Of course, I still have that 40/80m fan dipole I made in episode 10 ... I may try to put that up tonight or tomorrow (Saturday) morning at a height that will make it NVIS (a cloud warmer) - as that could be very helpful in the SS when a lot of contacts will be fairly close in. If it was a DX contest I would try to get it higher, or vertical, or in some configuration with a lower angle of radiation. I "only" have 4 antennas now ... maybe I need 5!?!?

I'll write about that in another episode, if/when I get it done.
Best rx & 73 (72) de kt8k - Tim