[Elecraft] P3 TX Mon: FEATURE REQUEST - Monitoring of

[Joe Subich, W4TV]

 > Plus, the required RF sample and IF frequency data is being
 > delivered by the radio to the P3 for tuning right now, isn't it?

No, the RF sample in transmit is diode demodulated (TX Mon).

> When I want to see my transmitted waveform, I will just rig up a
> serial switch to disconnect the serial port to P3 and view them that
 > way at a reduced level via IF bleed through.

The IF sample in transmit is potentially distorted transmit IF
signal *leakage* through other circuits that does not reflect
any contribution from the driver or KPA3.

> I shouldn't have assumed that the SDR functionality within P3 would
> have allowed both time and frequency domain displays of transmitted
> waveforms, even though I can see time domain waveforms on receive in
> both SSB andRTTY today.

The P3 specifications make it clear that one should not have expected
that.  Even if one were to add input switching to select between a
directional coupler sample in transmit and the IF in receive, the
frequency range of the P3 is limited to 21.7 MHz.  It could not cover
the entire 100 KHz to 54 MHz of the base K3 much less the 2 meter
transverter.

> Or just use my WinRadio SDR receiver as a SA.

Yes, with a directional coupler and appropriate attenuator.  I have
done that with my SDR/IQ for MF and HF but the SDR/IQ does not cover
six meters.

> Just seems silly to have to do all of that when I have a P3 just
> sitting there...

It would be possible if the P3 had the frequency range but it doesn't.

73,

   ... Joe, W4TV


On 9/15/2015 10:58 AM, Luis V. Romero wrote:
> Joe:
>
>
>
> I fully understand the distinction. However, I see the very same waveform on
> receive in the P3 today.  Why can't I see that waveform from my transmitter
> on the P3?  Plus, the required RF sample and IF frequency data is being
> delivered by the radio to the P3 for tuning right now, isn't it?
>
>
>
> I had the desired functionality on my Heath station 35 years ago. When I saw
> the "probe" hole in the P3 5 years ago I certainly expected similar
> capability to what I was accustomed in the analog SB610 to be delivered in
> the digital P3. However, expectation and reality of product features are
> only my personal opinion and nothing more.
>
>
>
> As it is, I waited five years and spent $200 to replace a 17 inch piece of
> wire.  I also cleared 12 inches of shelf space at my operating position by
> removing the O'scope from it and returning it to the bench.  Theoretically,
> I could even reclaim another three and a quarter inches by removing my Autek
> WM1 and simply use TX-MON's built in wattmeter feature, sell the Autek and
> recover more than half of the cost of TX-MON.
>
>
>
> I shouldn't have assumed that the SDR functionality within P3 would have
> allowed both time and frequency domain displays of transmitted waveforms,
> even though I can see time domain waveforms on receive in both SSB and RTTY
> today.  When I want to see my transmitted waveform, I will just rig up a
> serial switch to disconnect the serial port to P3 and view them that way at
> a reduced level via IF bleed through.  Or just use my WinRadio SDR receiver
> as a SA.
>
>
>
> Just seems silly to have to do all of that when I have a P3 just sitting
> there...
>
>
>
> -lu - W4LT
>
>
>
> PS:  I will just move on now with this thread.  No sense in beating a dead
> horse.
>
>
>
> You Wrote:
>
> The displays generated by K0SM are frequency domain ... TX MON is
>
> strictly a time domain (amplitude) display.  TX Mon uses a amplitude
>
> detector driven by a directional coupler.  To do what you desire would
>
> require an SDR tuned by frequency data (TX frequency) from the K3.
>
>
>
> The difference between an envelope (diode) detector and a tracking SDR
>
> is a couple of orders of magnitude in both cost and complexity.
>
>
>
>
>
>
>
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