I installed a GAP Voyager vertical about the beginning of October. The
ground has frozen now and the SWR dip has gone from 1830 to about 1820
now. I was curious why and the frozen ground theory makes sense.
-John NI0K
Michael Walker wrote on 12/3/2018 10:13 AM:
It would have to stretch about 4-5ft to see a difference of 50Khz in
resonance. I doubt it has stretched that far.
I see huge swings in my inverted L resonance (with 4 elevated radials) and
it is 100% related the ground freezing and unfreezing and ground
conductivity changing.
My 2:1 SWR points are about 80Khz apart. 2 months ago my resonance was
about 1850khz. Today it has slice up and the end result is that my SWR at
the bottom of the band is now 2.3:1 when it used to be 1.9:1. That is in 2
readings 28 days apart. My new low edge is 1813Khz. The easy fix is to
add 3ft tot he vertical part. In the spring, I will have to remove it
again.
I have before and after screen shots, but I don't think I can send them to
this reflector. If someone wants to see them, let me know and I'll send
them to you.
Like Don said, his broad bandwidth is due to ground losses.
Mike va3mw
On Mon, Dec 3, 2018 at 10:30 AM Don Wilhelm <[email protected]> wrote:
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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