Interesting P3 Anomaly

[Bob McGraw - K4TAX]

While working 6M this afternoon, I used my P3 Utility to capture the
stations signal that I was working.  While the capture was taking place,
about 3/4 through the capture screen, of course the P3 display had
frozen as normal during this time.   The station turned it to me, I
pressed the TX switch and started talking.  As soon as the P3 capture
completed, and I while was talking, I noticed an active waveform on my
P3.  After some further tests, I realized this is my transmitted
waveform being displayed on the P3.  {How do you like them apples?}

Normally one does not see their signal on their P3.  But in this case,
as the P3 Utility completed the capture and reverted the P3 to normal
operation, it was then capturing my transmitted signal from the IF stage.

Maybe I've missed this feature in the past.  Has anyone else come across
the phenomenon?   Certainly a nice feature to have as it does capture
the IF signal.  Changing power levels makes no difference.

And NO , I don't have the TX monitor option.

73

Bob, K4TAX


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[k6dgw]

Mine seems to see a little "bleed through" when I'm transmitting.  That
might be what you see?  Mine is weak from a K3, I don't have the TX Mon
option?

73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 3/15/2020 2:20 PM, Bob McGraw K4TAX wrote:

> While working 6M this afternoon, I used my P3 Utility to capture the
> stations signal that I was working.  While the capture was taking
> place, about 3/4 through the capture screen, of course the P3 display
> had frozen as normal during this time.   The station turned it to me,
> I pressed the TX switch and started talking.  As soon as the P3
> capture completed, and I while was talking, I noticed an active
> waveform on my P3.  After some further tests, I realized this is my
> transmitted waveform being displayed on the P3.  {How do you like them
> apples?}
>
> Normally one does not see their signal on their P3.  But in this case,
> as the P3 Utility completed the capture and reverted the P3 to normal
> operation, it was then capturing my transmitted signal from the IF stage.
>
> Maybe I've missed this feature in the past.  Has anyone else come
> across the phenomenon?   Certainly a nice feature to have as it does
> capture the IF signal.  Changing power levels makes no difference.
>
> And NO , I don't have the TX monitor option.
>
> 73
>
> Bob, K4TAX

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[Brian Hunt]

As I recall, if you disconnect the RS232 thru the P3 to the K3 it the P3 will display your spectrum since it doesn't know to mute during TX. Someone from Elecraft said it was due to "leakage" and is at IF so doesn't represent your transmitted signal. Seems like you found a software way to do this. :-)

73,
Brian, K0DTJ
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[David Box-2]

Don't know what you mean "doesn't represent your transmitted signal"  It is leakage of your signal at the IF, I see it with my SDR that is tied to the P3 IF out and it looks exactly like the signal I see on a spectrum analyzer using a coupler.
de Dave K5MWR


On March 15, 2020 8:11:07 PM CDT, Brian K0DTJ <[hidden email]> wrote:

>As I recall, if you disconnect the RS232 thru the P3 to the K3 it the
>P3 will display your spectrum since it doesn't know to mute during TX.
>Someone from Elecraft said it was due to "leakage" and is at IF so
>doesn't represent your transmitted signal. Seems like you found a
>software way to do this. :-)
>
>73,
>Brian, K0DTJ
>
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[k6dgw]

It doesn't "necessarily" represent your transmitted signal, but in your
case, it seems that it is, or at least very close.  Likewise for me. 
There are amplifier stages following the IF which can [and often do]
introduce distortion which won't show up if monitoring the IF frequency.

73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 3/15/2020 8:09 PM, David Box wrote:
> Don't know what you mean "doesn't represent your transmitted signal"  It is leakage of your signal at the IF, I see it with my SDR that is tied to the P3 IF out and it looks exactly like the signal I see on a spectrum analyzer using a coupler.
> de Dave K5MWR
>

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