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| Author |
Message |
ball
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30 metres
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Jan 18 04:03 UTC 2008 |
I want to try 30m. My first thought was a half-wave
dipole. Does anyone here know of alternative antenna designs
that work well on 30m?
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| 17 responses total. |
tod
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response 1 of 17:
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Jan 18 19:05 UTC 2008 |
There's NEC4WIN95 and a crack floating around on the 'net. Not that I'm
advocating not purchasing the product but it may be worth a trial.
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ball
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response 2 of 17:
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Jan 19 01:25 UTC 2008 |
I'm guessing that's antenna design software, probably for Microsoft
Windows, which I don't run.
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rcurl
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response 3 of 17:
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Jan 19 05:51 UTC 2008 |
Why not a dipole?
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ball
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response 4 of 17:
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Jan 19 21:34 UTC 2008 |
Re #3: That's the obvious solution and I'll have a go if I
can find a sensible place to string one. I just wanted to
make sure I wasn't overlooking a sound alternative.
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tod
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response 5 of 17:
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Jan 19 23:31 UTC 2008 |
re #4
If you do go dipole, you might as well go the extra step and make it a rhombic
for some db gain.
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krokus
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response 6 of 17:
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Feb 1 22:46 UTC 2008 |
Rhombic are too directional for casual use, they are typically used
for fixed-base, point-to-point connections.
Any antenna design that is decent will work for 30m. You could you
a Zepp antenna, or a G5RV.
Are you looking for something that is basically omni-directional? Or
do you want some directional control? (Even a dipole has some
directionality to it.)
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rcurl
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response 7 of 17:
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Feb 3 19:56 UTC 2008 |
If you wantr non-directionaL - use a vertical.
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ball
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response 8 of 17:
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Feb 5 02:55 UTC 2008 |
A half-wave dipole for 30m would be 15m long, which is
impractical at my current location. Even a quarter-wave
ground-plane antenna would be unwieldy. I've thought about
using a dipole mount and a couple of helically-wound mobile
fibreglass whips, but I don't think it would be very robust.
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rcurl
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response 9 of 17:
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Feb 5 03:28 UTC 2008 |
You can reduce the height with loading coils. This is standard practice for
mobile HF.
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gull
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response 10 of 17:
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Feb 6 20:29 UTC 2008 |
You could wind a helix on PVC pipe. I have an old CQ article somewhere
that gives the formula for HF helixes; if you need that info I can dig
it out.
If you have a house with a non-metallic roof, you could also try a
"droopy loop" -- a full wave loop draped over the roof, secured near the
eaves at the corners. For 30m a rectangular loop would be about 33 feet
long and 16.5 feet wide. You'd feed it with a 2:1 balun. But I'm
guessing if a dipole is out of the question you probably aren't in a house.
If all else fails, put up the longest wire you can and feed it with an
antenna tuner.
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keesan
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response 11 of 17:
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Feb 6 21:17 UTC 2008 |
We use our metal roof as an antenna.
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rcurl
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response 12 of 17:
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Feb 7 17:28 UTC 2008 |
For transmitting? What is its radiation impedance?
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keesan
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response 13 of 17:
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Feb 7 18:54 UTC 2008 |
For receiving. We have a metal cupola about 4x7' on edges and we moved the
end of the antenna cable to various spots until we found one that gets three
stations (Toledo, Lansing, Windsor) and attached it to the wood sheathing.
FM quarter wave (?) is about 5' and we are about 2' from a roof edge.
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rcurl
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response 14 of 17:
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Feb 8 05:32 UTC 2008 |
It's a different problem when transmitting, which is what the item is about.
You have to tune the antenna system so that it presents an apparent resistance
impedance or you can burn out your transmitter (well, at higher powers).
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ball
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response 15 of 17:
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Feb 8 22:19 UTC 2008 |
Do we have an item for broadcast reception? If not then I
think we should create one.
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krokus
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response 16 of 17:
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Feb 29 21:14 UTC 2008 |
re: dipole length
Don't forget that a dipole doesn't have to be strung in a straight line.
It can be run in a zig-zag, if that will fit your layout better.
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ball
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response 17 of 17:
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Feb 18 18:37 UTC 2009 |
I may see if I can put a short pole on the East end of
the house. For now I could put a J-pole on it and eventually
I might even be able to droop a dipole between that and the
tower, which is on the West end.
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