Antenna wire question - full size 160m dipole, others
I spotted the solid 12 gauge copper clad steel at the wire man. Has anyone used it before? What can you tell me about it, and what other wire can you compare it to?
What I am after is a full size 160 meter dipole. I am also contemplating adding 80 and 40 to it as a fan dipole. What thoughts can you share for adding the other bands? Is it worth it? Will I loose any noticeable performance over a single band?
The location I am wanting to put this up is a temporary location for Field Day and potentially the state QSO party. There is a 180-200' tower available on one side and a 50-60' tower available on the other as a support. The antenna would have to be self-supporting the whole length between (hence wanting to use the copper clad steel - a full span on 160 and feed line will put a lot of tension on it, plus if I add the other bands the main run will have to support that as well).
Feeding the antenna:
I am going to be running coax to it. How about a 1:1 balun at the feed point vs. direct coax feed? My gut tells me a 1:1 balun is the better route but I've also been using direct coax feeds on all my dipoles for years. The only time I run a 1:1 balun is with balanced line and a tuner.
-Copper clad steel has been used for decades and decades by both hams and the telephone industry. Probably the strongest wire you can use. Avoid nicking it so the steel does not become exposed and rust.
-Some point out that as frequency decreases skin effect of the copper cladding can become a factor for decreasing efficiency, esp at 160m. Something to explore and consider. On the other hand, most hams would be ecstatic if they had the room to hang a 160m dipole and gladly accept some loss in efficiency.
-A balun helps keep radiation off the feedline, for both rx and tx, improving efficiency and decreasing common mode noise on rx. That's a pretty good reason to consider using one for low band antennas used on several bands. On the other hand a balun is not strictly required.
-I have no idea why you would use a balun on a purely balanced line feed for a dipole.
 A 160m dipole will be close to resonance on 80m and 40m. It really serves no purpose to add elements for those bands as long as your tuner can handle the impedances. A balance wire feed would be ideal, but coax is acceptable.
-If you don't have it already I would strongly encourage you to buy the ARRL Antenna Handbook, and ON4UN's Low Band DXing (it isn't strictly about DXing). These have a wealth of knowledge.
p.s. Please don't gloat too much in front' of us poor slobs who don't have room for the big wires!
Last edited by KB4QAA; 06-28-2012 at 12:56 PM.
Author of: Mr. Fred, Nuke This Forum (Danger Close)
CCS is fine, if it's good stuff.
A 160m dipole cut to 1.8 will resonate at 3.6 and 7.2 MHz for sure, but the feedpoint impedance on those two bands (80m and 40m) will be very high and a terrible match for coax. If you use low-loss coax and it isn't too long, and a very good tuner, you might be able to use the single dipole on all three bands but without a good tuner that could be rather hopeless and the tuner behavior will change a lot with coax line length.
I like the parallel dipole idea better, as if you do it all well, your line loss will be minimized and you won't even need a tuner.
Using a good 1:1 current balun at the feedpoint is always a good idea. It will take a lot of ferrite for 160m, but there are several popular combination current balun/center insulator products on the market that use at least fifty ferrite cores internally and do work down to 1.8 MHz. Even the relatively inexpensive model B1-4K ULTRA from Radioworks seems to do okay on 160 (I've had four of them).
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The fan dipole will work but with the wires run in line as you will I have found each band needs to be trimmed. To keep the weight down I would feed it with RG-58 and no balun.
I've tried 160 meters on FD before and there is almost no activity. But 80 is a must-have.
Thanks for the information. The weight is a consideration, but it isn't going to be hanging at any location for a very long time - only FD and the state QSO party maybe. I wish I could have something like that all the time, that would be pretty cool!
I never gave any consideration to the frequency capacity of a balun. I was even thinking of making my own, might have to do some more research in that.
I'll check the antenna handbook and low band DX'ing. I have both, not current issues though.
The wire is 30% 12 gauge. I would think the thicker gauge would help out - 30% of 12 gauge would be thicker copper than 30% on 16 gauge, I don't know if that has any merit or if the skin depth is within that range on the 12 gauge (haven't calculated it, not sure it matters too much realistically though - I've used 26 gauge magnet wire and .050" stainless for antennas before and worked the bands, not 160 or 80 though, but 40 a lot).
For the last rebuild of my 80 and 160M dipoles I just used the #14 THHN rated stranded, plastic clad house wire from the big home & builder's supply store. I got a 500 ft roll and maybe saved a bit for bulk prices. I ended up building several antennas and still have some left over for repairs.
I don't use bare copper because my wires loop over a lot of branches in the woods and need to be insulated.
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I used the copperclad in the islands with about 12 turns of the feed-line (RG214) wound about oatmeal box diameter at the feed-point and it worked very well.
I then took the coax off and went with ladder line and the results were measurably better.