[TowerTalk] dipole length adjustment
xdavid at cis-broadband.com
Sat Jan 20 14:16:50 EST 2007
Yes, the EDZ is a very nice configuration and it sounds like you have a
nice setup. I'd be tempted to try the same thing myself for 80m and
160m except that the long ladder line would have too large a surface
area for the wind gusts we get here.
There are ways to make a "single" antenna work better on multiple bands,
though. I normally dislike fan dipoles since most people cut each
section for resonance on a particular band and they get all sorts of bad
patterns as a result, but with a tuner you can choose the segment
lengths so that none of them are resonant on any band and the patterns
for each stay pretty good. Two non-resonant dipoles in a fan
configuration should decently cover 40m and above, and three would
probably give 80m as well. I'll try to come up with some lengths if
anyone is interested.
Joe Giacobello wrote:
> Agreed, but there's a lot to be said for getting on all bands with one
> piece wire even if the radiation pattern is not optimum for a
> particular direction. They're tough to beat for a general purpose
> antenna. Obviously, if one has options for multiple antennas, phased
> arrays or rotatable directional antennas, they're the way to go.
> I currently use an 80M EDZ fed with balanced feed line on 40, 80 and
> 160M. On 80 I get 3 dB gain broadside vs a dipole, and on 160M it is
> effectively a dipole. On 40M I use it to get omni-directional
> coverage, more or less, for a weekly 40M SSB net.
> 73, Joe
> David Gilbert wrote:
>> That's true to a point. I have used efficient homebrew antenna
>> tuners my entire ham radio life and wouldn't be without one. But you
>> can get some REALLY ugly radiation patterns from trying to use the
>> same antenna on several bands. The antenna may tune fine and still
>> not be putting your RF even close to where you want it to go. I
>> always tried to stay reasonably close to a half wavelength ... for
>> example, using a 50 foot dipole for both 20m and 40m still gives a
>> fairly clean pattern on both bands.
>> Dave AB7E
>> Donald Chester wrote:
>>> The best way to solve the problem once and for all is to feed the
>>> dipole with open wire tuned feeders, using a balanced, link-coupled
>>> antenna tuner. That way you can instantly change the resonant
>>> frequency of the antenna to any spot in the band from the comfort of
>>> the operating position. And one dipole can cover multiple bands
>>> without traps or other jury-rigging.
>>> Don, k4kyv
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