[Elecraft] wire antennas

[Stephen W. Kercel]

Scott:

I use several fan dipoles. Both use two elements. One operates on 40 
and 30 meters (and I get 15 meters, 3rd harmonic of 40,  free into 
the bargain, but the SWR is a bit above 2 on 15 m, and I must use 
tuner to match it to the K2. ). The other antenna operates on 80 and 
20 meters (and I get 17/12 meters, 3rd and 5th harmonic of 80 meters 
free into the bargain, but the SWR is a bit above 8 on 12/17 m. I 
must use tuner to match it to the K2 on 17/12. However, the line 
losses are acceptable, and the antenna is very effective on all four bands. )

Several gotchas. The elements do interact. The shorter element will 
be non-trivially off from the "468" formula. The longer element is 
pulled much less noticeably. However, if you're looking for low SWRs 
of both bands, be prepared to do a lot of tweaking.

I agree with other posted comments. If you use more than 2 elements, 
be prepared to do a very great deal of very frustrating of tweaking.

Very important: Construct your antenna in such a way that the short 
element cannot wrap around the long one. If it does wrap, it will 
pull your painstakingly tuned antenna way off the desired resonant frequency.

Other caution: Do not suppose that you can simulate a fan dipole on 
EZNEC. The condition of two parallel elements of unequal length very 
close together is one place where the computer model departs from reality.

I do not use baluns, and it does not seem to have caused me any trouble.

Good luck,
Steve
AA4AK


At 04:44 PM 2/19/2007, wsm at amaonline.com wrote:
>Hi
>This is a little off topic, but I don't know of a better place to
>find someone that would know the answer to my question.
>Many years ago I used one coax to feed three different inverted V
>antennas all for different bands. At the time I thought they worked
>just fine. Worked all kinds of dx with the setup. I have been told
>lately that the unused antennas on the setup would pick up additional
>noise.
>Has anyone ever done any testing with multiple antennas on one
>feedline to see if they really do pick up extra noise?
>I'm thinking about putting up new inverted V antennas on 160, 80, and
>40 meters and feeding them with one coax. Sure beats antenna
>switching and it always seem to me that the signal would go to the
>resonate antenna. I always used a coaxial balun in the feedline.
>Any ideas would be appreciated.
>Thanks
>Scott N5SM
>
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