[Elecraft] 80 Metre Verticals

[Guy Olinger K2AV]

Concurring with Tom, assuming you have the polarity of the X correct, and
there's more.

A short 1/4 wave-ish vertical that shows R=57 in the R+jX expression is a
vertical/counterpoise or radial(s) combo that has far too much resistance
and is a dead giveaway for a considerably inefficient antenna and may be
wasting 3 dB somewhere.

A full quarter wave vertical over 60 1/4 wave radials should be showing
32-35 ohms at resonance, e.g. 33+j0. A theoretical 1/4 wave L in free space
with lossless conductors should be 12-15 ohms. In the real world over real
dirt with an efficient counterpoise, and lacking various possible
real-world inefficiencies an L should be something roughly 25 ohms. Mine is
28 ohms on a calm day over dried out dirt.

Frankly, if it really is efficient, 57-j130 sounds like a fairly *longer*
than 1/4 wave-ish L aerial wire over an FCP without using an isolation
transformer. A bad idea for a stack of reasons.

Otherwise, there is likely a lot of dielectric material inside the bend of
the L adding loss in the R measurement in addition to 32-35 ohms. An
efficient L should show lower R yet to be efficient. Mine is 28 ohms,
measured with an AIM4170 with a calibrated feedline factored out by the
software. An occasional measurement right at the feed is always very close.

In your case R = 57 instead of R = 28 probably means that something like 29
ohms of that 57 is recoverable loss for some reason or other.

73, Guy K2AV


On Tue, Feb 28, 2017 at 10:05 AM, Tom Boucher <tomg3olb at gmail.com> wrote:

> Fred,
> If your inverted 'L' was a bit less than a quarter wave long, it would have
> been capacitive and showing 57-j130  (not plus). In which case you needed a
> small inductor to match it to your 50 ohm coax, not a capacitor.
>
> 73,
> Tom G3OLB
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to k2av.guy at gmail.com
>