Re: Flumoxed

Posted by N2TK on Dec 05, 2018; 9:19pm
URL: http://elecraft.85.s1.nabble.com/Flumoxed-tp7646765p7646835.html

A number of years ago, the SWR on my shunt fed tower kept getting wider and
flatter. The feedline buried hardline with an aluminum jacket.  The soil
here in upstate NY had eaten away the aluminum and produced a goo. When I
disconnected all the feedlines to the tower the shield on the 160M feed
showed a high resistance.  
The shield of the other feedlines were providing the return path. So, nice
SWR but not a very efficient antenna.
73,
N2TK, Tony

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Don Wilhelm
Sent: Monday, December 03, 2018 10:07 AM
To: [hidden email]; [hidden email]
Subject: Re: [Elecraft] Flumoxed

Not necessarily - notice the relatively flat SWR (less than 2:1) over a
large frequency range (for 160 meters).  That normally means that the
antenna is acting more like a resistance than a radiator.

I would expect the SWR on 160 meters to be low only over a 25kHz or at most
50kHz range of the band.

When the SWR bandwidth of an antenna increases, you should be looking for a
problem in that feedline, antenna to feedline connections or in the case of
a vertical, the ground radial system.

One possibility is that the radial wires installed were aluminum - they do
not last very long in the ground, for some reason, moles like to chew on
them.

73,
Don W3FPR

On 12/3/2018 9:18 AM, Don Roberts via Elecraft wrote:
> Lee, it looks like your inverted L wire has stretched. Check with an
antenna analyzer and you will probably see your resonate frequency is lower
than 1.8 Mhz. Perhaps time to do some triming.
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