[TowerTalk] Vertical question

[Lux, Jim]

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
>> _______________________________________________
>
>
> 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.