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HyTower on 160 woes
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by AB3CX on November 2, 2009
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I have a HyGain HyTower vertical, it's the basic antenna with none of the extras for 160M. Works fine. In the past, I had discovered that I could use an extreme setting on my Ten Tec 238B tuner and get an acceptabe SWR on about 1820-1835 for some 160M work, and in fact 4 days ago worked several stations in EU doing that. One week before that, I replaced the main coax run from the tuner out to the antenna. Two days ago I shortened the terminal piece of coax by about 10 feet. I also re soldered connections at the HyTower base, including to the center wire up to the stinger at the base. I soldered with apropane torch, silver solder and flux,my joints are good. I also drilled through a new hole in the base for a fresh screw mount, as the old drilled hole site was a bit rusty; I have all clean and nice terminations now. The Antenna works a bit better on 80-10M bands now in terms of bandwidth and SWR, but no matter what I do, it won't load anymore on 160M with any tuner settings at all. Was not sure why, except for the shorter coax run, so I tried re inserting various lengths of coax again. Inserting about 20 feet of coax left laying on the ground near the antenna lets me get an acceptable tuner setting combination again, but inserting the same extra length of coax inside just beyond the tuner inside helps not at all. Wondering if anyone can devine what might be going on. Of course I could put up an true 160M antenna.............
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RE: HyTower on 160 woes
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by WX7G on November 2, 2009
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The length of coax between the antenna and the tuner is rotating the impedance around the Smith Chart. Apparently the tuner prefers one position. Use this and you're on the air.
Inserting an extra length between the tuner and the radio will make no difference as this line has a low VSWR.
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RE: HyTower on 160 woes
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by AB3CX on November 2, 2009
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Thanks for the reply. I dug the same piece of coax out of the corner I threw it in, put new connectors on it and put it back in line, I'm about where I was 2 days ago, the tuner settings for 160 are about like before, slightly different for 80M but close enough. Educational.
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RE: HyTower on 160 woes
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by KU3X on November 3, 2009
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I may be missing something but if I remember correctly, the Hy Tower is only 10 to 80 meters. A friend of mine had one and here is what we did to get it to work on 160 meters. He purchased a 40 meter trap and installed it at the top of the tower sections. Not the top of the 80 meter mast that sticks out of the top. So now you have a trap at the top of the tower and what you are going to make is an inverted L. I don't remember how much wire is needed but you will probably add about 90 feet of wire to the trap and run it in any direction away from the tower. Borrow and MFJ 259 and see where the thing resonantes. Like I said, I don't remember how much wire is needed but it does work and work well. You will not loose any of the bands from 10 - 80 meters. You just added 160 meters.
Barry, KU3X
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RE: HyTower on 160 woes
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by AB3CX on November 3, 2009
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You are correct in what you say. What I was pointing out is that it is possible to force it to work on 160 meters without that trap and the 120 foot piece of wire. The other setup sold to make it work on 160 is the base loading coil. My amazement is that the bare bones 160M function depends on the length of the coax feedline. Since a wavelength on 160 M is(even considering the velocity factor in the coax) at least 400 feet, it's hard for me to understand how a 10 to 14 foot piece of coax makes enough difference to be able to load it, but it does.
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RE: HyTower on 160 woes
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by N3OX on November 3, 2009
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"it's hard for me to understand how a 10 to 14 foot piece of coax makes enough difference to be able to load it, but it does. "
We can work this out.
The Hy-Tower is what, 60 feet?
A 60 foot tall, 8 inch "diameter" vertical shows an impedance in EZNEC of 5-j304 if fed against an excellent ground.
I can use VK1OD's transmission line calculator to do transformations. 50 feet of RG-213 coax transforms 5-j304 to 0.76-j43.1 at a cost of 5.2dB.
If I cap W9CF's tuner simulator inductance at 25uH, that gives a "tune failed" giving a minimum SWR of 2.3:1 (and another 9dB of loss)
If I lengthen the coax to 55 feet, the impedance at the tuner is 0.9-j24 (and 7.4dB loss). Now W9CF's tuner simulator will find a 1:1 match (with 8.4dB loss)
Small changes in the feedline make big changes in the impedance, especially in the reactive part, and since your tuner is already at an "extreme" setting, it doesn't have very many options.
Of course the system is probably so bad that it's not worth worrying about fixing it with or without extra coax. If its working for you with the extra, go for it.
Otherwise, if you really want that antenna to work well on 160, I'd add a loading coil at the base with some relays to kick it in and out as the simplest start. You probably need about 27 microhenries. Make it 30 to be on the safe side... something like 30 turns on a 4 inch form should get you started. #10 wire is fine, 1/4 inch copper tubing, though pricey, might be easier to wind. I've got access to a lathe so I use the wire:
http://n3ox.net/projects/stepperswitch/160_match_lg.jpg
Trying to run coax as a tuned feeder to low resistance antennas with lots of capacitive reactance is a disaster. The currents get huge because of the giant amount of reactive power (stored energy moving around) and if you have to run them in coax and/or use the coax as part of the energy storage it doesn't work too well. And it's still touchy and fiddly despite all the loss, as you've determined.
There's basically no worse antenna to feed with a tuner through coax than low resistance highly capacitive antennas. A lot of people think the really HIGH impedance ones are the worst (like center fed full waves), but you could feed 3000 ohms through 40 feet of RG-213 on 160m and clock in under a dB mismatch loss.
You could easily drop 10-20dB in a system like this and still have it be rough on your tuner. That won't necessarily stop you from working DX.
I estimate about I have about 25% efficiency with respect to a full size vertical here and I've worked a few stations in Europe running QRP 5W to the antenna... about 1.25W ERP. And I worked 116 DXCC with 100W applied before I built an amp. Now I run 400W, 100W ERP, and almost feel like an alligator (it's pretty noisy here).
But when a simple coil of tubing and a couple of reasonably high voltage, high current capable relays can make most of that loss disappear in a weekend, it might be worth it to make that your next project.
73
Dan
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RE: HyTower on 160 woes
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by KU3X on November 4, 2009
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I didn't realize that you were just trying to force a coupling between the tower and the rig. Just get a better tuner but that's not the proper answer.
I built the untimate antenna tuner from the ARRL handbook over 30 years ago. That thing with couple a Matag wash machine to operate on 160 meters. But the match is worthless.
I learned many years ago that, " a resonant antenna radiates the most RF !" I just wanted to point out a better way to get on 160. A lot of people have no idea of the method I mentioned above, and it works great.
Barry, KU3X
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RE: HyTower on 160 woes
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by AB3CX on November 4, 2009
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Thanks for the very thoughtful answer. Indeed it would be better to put the loading coil in place. Basically that 30 uH is in direct series with the center conductor of the coax and the antenna, yes?
I rarely go on 160M except for contests to get some extra mults, so unfortunately I have under efforted this band as far as my antenna system. The fact that some contest stations have great ears has abetted my laziness!I want to do better in the CQ WW coming up, so will get the coil wound with tubing, that sounds like the way to go.
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RE: HyTower on 160 woes
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by N3OX on November 4, 2009
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"Basically that 30 uH is in direct series with the center conductor of the coax and the antenna, yes?
"
Yeah. You'll still have a mismatch (due to the low resistive part) that way and so you'll still need to use your tuner but by cancelling all that reactance you'll have much less line and tuner loss.
You can match up to 50 ohms with a shunt coil between the coax center/coil junction and ground, but that requires more complicated switching in and out..
With just the series coil you could potentially use a shorting relay across the coil to short it out when you don't want to use it.
That relay will need to withstand at least several thousand volts if you run high power....
Another advantage of simple series coil and tuner is that the match is rather narrow. I have to use a variable system here to tune across the band anyway, so series coil and shack tuner is probably a good way to go given your goals.
73
Dan
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RE: HyTower on 160 woes
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by WB8VGE on November 7, 2009
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boys...
I wanted to partake in the 160 meter contest that is coming up, so I managed to find a coil that looked about the same size as the one hygain sells for $100.
stuck in on the bottom in series with the wire that comes from the top.
mfj thingiee says ok on 160 meters with a winding or two out with a clip lead.
now...
that coil threw all the other bands in the pooper!
just wondering if that is common, even with the hygain coil, or just what's up.
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