Next weekend is the long Thanksgiving Day Weekend here in the US. After the holiday on Thursday, that leaves me with three days off. If the weather is not bitterly cold (which it is not supposed to be), I am thinking of taking down the W3EDP and putting up a random length doublet in its place. Of course, this is all depends on no surprises coming out of left field that could possibly occupy the entire weekend. You know what they say about "The best laid plans of mice and men ......"
The main objective would be to get the wire higher than it currently is. I am going to follow the old rule of thumb - "Get up as much wire as you can, as high as you can." This is the antenna that I used for so many years as a Novice and it served me well. I think I still have a Ten Tec Antenna T kicking around in the basement.
Basically, I would get that up as high in the maple in the backyard as I possible could, and then run as much wire as I could to each anchor point. I will feed it with 450 Ohm window line to the ground, to a balun (A few years back, Bob W3BBO made me a beautiful 4:1 that I still have), and then RG213 to the shack.
Off the top of my head, I am thinking I'd have about 50 feet of wire to one side and about 70 feet of wire on the other. The main thing, though, is that I'm hoping I can raise the wire level from about 25 or so feet to about 40 feet.
This would be my customized version of "The 4$ Special" antenna.
Ah, the joys of living on a small, suburban lot!
You might be thinking, "Why did he wait until now? Why not do this in the Summer, when the weather is more comfortable?"
I'll tell you why - most of the leaves are gone now. Hopefully there will be less snags and fewer #$*&! words uttered.
72 de Larry W2LJ
QRP - When you care to send the very least!
Larry, I'd try it with a couple of different choices than the ones you indicate.
ReplyDelete(1) Instead of having 50 ft on one side of the feedpoint and 70 ft on the other, I'd feed it in the middle unless that made the feedline come down at too acute an angle to the antenna. In that case I'd settle for less than 120 ft but still feed it in its middle and with feedline as nearly at right angles to the antenna as possible. Motive: reduce common mode current on the feedline so your balun will have less work to do.
(2) I'd at least first try a 1:1 current balun instead of a 4:1 balun. See http://www.karinya.net/g3txq/tuner_balun/. He has data showing that only rarely is a 4:1 balun a better choice than a 1:1 balun.
David, VE7EZM and AF7BZ
I agree with David above. I'd feed it in the middle, and I'd use a 1:1 current balun. The 1:1 current balun is a better choice when dealing with the complex impedances of an untuned doublet.
DeleteYears ago, I had a Loop Skywire (a 1 wavelength 80m loop) at about 15 feet, and replaced it with an untuned doublet at 45 feet. The untuned doublet worked way better.
ReplyDeleteThanks, guys. If I feed it in the middle, that would MAYBE give me 50 feet each leg. Guess that would be OK. I have a 1:1 in storage in the basement. Thanks for your advice. As always, it's greatly appreciated!
ReplyDeleteHappy Thanksgiving!
Go for it! But make sure your 1:1 balun is a current balun, not a voltage balun. If not, you can make one in about 10 minutes if you have the coax and toroid on hand. Put the balun in a non-conducting case since capacitance to a metal case can mess things up.
DeleteThe 93 ft ZS6BKW modification of the 102 ft G5RV antenna can work pretty well on 80 m, and some people even use 88 ft, though that's beginning to push feedline losses on ladder line a bit too high (but losses aren't that bad with real open wire line). On the higher bands aside from pattern differences I don't think there's much to choose between 132 ft, 102 ft, 93 ft, and 88 ft. The 88 ft length is the longest one that will be essentially only broadside up through 20 m.