[prev in list] [next in list] [prev in thread] [next in thread] 

List:       elecraft
Subject:    Re: [Elecraft] P3 Panadapter - strong sum signals & relays clicking
From:       Alan <n1al () sonic ! net>
Date:       2019-01-27 18:31:39
Message-ID: 3b9dc57b-b518-703a-481d-dc8f25a8aecd () sonic ! net
[Download RAW message or body]

Yes, the P3 automatically bypasses its internal preamp whenever the 
input signal level overloads the ADC.  It uses a fairly complicated 
algorithm to try to minimize the inconvenience.  The first time the ADC 
overloads, the preamp is switched out for a fairly short period of time 
and then it is switched back again to see if the overload is still 
present.  If so, the preamp is turned off again, but this time for a 
longer period.  This continues until eventually the OFF period is quite 
long.  (I don't remember the exact time periods.)

It takes quite a strong signal to overload the ADC so most operators 
will rarely see this.

The gain of the internal P3 preamp is about 19 dB.  The software is 
supposed to take that into account in the display so that signal levels 
remain accurate when the preamp is switched out.

Alan N1AL


On 1/27/19 2:40 AM, Roger wrote:
> Hello,
>
> since I worked on 80 and 160 m the last couple of weeks I noticed that the
> P3 panadapter starts clicking relays whenever a very strong local signal
> (-10 dBm to 0 dBm)  or a number of strong signals within the bandpass are
> present. I could not find a relation yet when it happens because it takes
> place in irregular intervals. I donīt notice this behavior on the upper
> bands where signal levels and even the sum signals are not as strong as on
> the lowbands. I also donīt notice it if I switch to a nonresonant antenna
> and dropping the signal level or terminate the receiver to actually mute it.
> So it has to do with the signal level which makes me think it is an
> automatic adaption to keep the A/D converter in the dynamic range. It also
> seems to have a time constant as it doesnīt switch around quickly but keeps
> a certain state until it switches again. The fact that the noise floor on
> the screen jumps up by 50 dB or and then drops down again hints to an
> automatic adaption mode. Attenuator setting on the radio doesnīt have any
> effect.
>
> As I didnīt find any information about this issue in the manual I wonder
> whether somebody with a P3 panadapter could confirm (or not) whether he/she
> experiences the same thing. It was quite present this morning on 160 m (CQWW
> CW 160 m) as the band was filled with 9+++ signals between 1810 and 1900
> kHz.
> I hear the sharp noise of the relays clicking thru the headphones and it
> gives an uncomfortable feeling to hear the relays cycling all the time.
> Maybe a future update of the firmware could make the switching process a bit
> smoother
>
> The firmware in use is the latest - ver. 1.60
>
> 73/Roger - DL5RBW
>
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft@mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to alan@elecraft.com
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to elecraft@progressive-comp.com
[prev in list] [next in list] [prev in thread] [next in thread]