On 3/16/21 2:53 PM, Lux, Jim wrote:
On 3/16/21 2:50 PM, Richard (Rick) Karlquist wrote:
On 3/16/2021 12:15 PM, Jim Brown wrote:
On 3/16/2021 7:14 AM, Mike Smith VE9AA wrote:
Most of the time through an A/B switch the verticals were close
enough that
I would really be guessing which one was loudest/best and other
times the
one with all the 60 on-ground radials was definitely best by a
small margin.
The fly in the ointment with listening tests is AGC. A FAR better
test is A/B RBN testing, alternating between the two antennas for a
half dozen "TEST VE9AA" on one, QSY, then the other, pause 10
minutes, QSY, repeat at least a dozen times, and average the results.
73, Jim K9YC
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What has always worked for me is to simply turn down the
RF gain and/or change the AGC threshold such that there
is no AGC action. It is then possible to switch back and
forth while listening and hear the increase or decrease in
loudness. This does of course require a signal on the air
to use.
The problem with RBN is that is measures S/N, not absolute
amplitude. The noise floor is not necessarily the same at
two different frequencies or times. In this case S/N doesn't
correlate with signal strength. Possibly you could fix this
by swapping the frequencies every other time.
What about using one of the many WebSDRs - you can get a raw, no AGC,
I/Q stream from many of them. Or maybe there's a way to measure signal
strength off the screen - since they're wideband receivers, the "pan
display" is probably no AGC.
http://www.websdr.org/
http://websdr.ewi.utwente.nl:8901/
gives power in dBm from a whip. No apparent AGC
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