[TowerTalk] Vertical question

[Lux, Jim]

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
>>> _______________________________________________
>>
>>
>> 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