[hpsdr] Penny PTT unkeying spike - T/R sequencing?

[Phil Harman]

Hi Tom,

I normally run KK in full duplex mode and have not seen this effect.
However, I've not used AM or FM for a while so will check tonight and also
under PowerSDR(TM).

I did add TR switching to KK some time ago but it does not seem to have
made its way into the current release. I'd add it back in.

PowerSDR(TM) did support TR sequencing for the SDR1000 and has a front
button marked 'X2TR'. This was applied to the X2 connector on the SDR1000
boards.

I'm not sure what effect this button has, if any, when using HPSDR boards.

Perhaps one of the PC programmers could look through the PowerSDR(TM)code
and see if it could be included in the PTT function.

TR sequencing is an essential item in any SDR software.

73 Phil...VK6APH



> ***** High Performance Software Defined Radio Discussion List *****
>
> With a lot of email help from Joe/K5SD and Frank/WA1GFZ,  I have the new
> HPSDR rig running!  Thanks much guys!
>
> In the past week I've done a lot of bench testing and find Penny to be a
> very clean exciter. I especially like the IMD and opposite sideband
> suppression figures. With Mercury, what a combination.
>
> Now, I've run across something that may need more refinement. I am out of
> solutions. I am seeing (and hearing) the effects of a spike during PTT
> UNKEY. One symptom is a small spike 2khz above the main carrier frequency.
> To see and hear it, PTT key Penny on AM or FM while watching the Mercury
> panadapter or other scopes - then UNKEY and you will see this pulse ramp
> up
> as the main carrier drop down. It will last maybe 50 ms and be down about
> -30db from main carrier. (At least on my rig)  On the Merc "scope" feature
> you may see the tone oscillation as it cuts off, and faintly hear it in
> the
> headphones.  My S-meter bangs up to about 40-60+ over and I hear a rushing
> pop in the headphones for maybe 500 ms.  (T/R sequencing amiss?)
>
> On a separate receiver I can hear the after-spike as a clean carrier
> pulse,
> weak, but still there.  I could be wrong, but I think my particular spike
> level is somewhat higher than others because I compared it to Frank's
> Penny
> over the telephone and found his pop, S-meter and spike level down lower,
> but still there.
>
> ** This 2kz removed spike may NOT be related to the sequencing timing
> S-meter and headphone pop however.  I mentioned it for reference.
>
> I changed the firmware version and changed the PSDR to different versions
> and saw no difference. I checked supplies for stability and ran many other
> tests but had no luck in smoothing out this T/R sequencing.  If I
> disconnect
> all cables except for the USB and power supply - and key Penny using the
> MOX
> mouse, the spike is still there. Same with external keying.
>
> The problem is a number of times it seemed this T/R sequencing noise
> caused
> Penny to loose its programming and lock into a full dead carrier of 500
> mW.
> I had to reboot and repower the hardware to recover.
>
> The reason I'm bringing it up is that I've had a lot of experience with
> T/R
> sequencing homebrew transmitters and receivers and see the symptoms here.
> Is
> it my particular lash up or do the rigs vary in this area? Maybe there is
> something that can be done in firmware or software to lengthen or better
> sequence  the T/R transition to smooth things out so that Penny  drops out
> more quietly and the pulse is lower in the headphones, Smeter bang lower
> and
> on the panadapter.  I checked with two others - one said he had the
> s-meter
> bang and the other did not.
>
> Other than that, I dearly love the overall performance of the transceiver
> and look to add on an MRI (-50db IMD) linear amplifier and go from there.
>
> Thanks again for all who have helped.
>
> BTW, Phil is working on that .bat file to permit audio line input to
> Penny.
> Will post it when tested.
>
> 73,
>
> Tom Cathey, K1JJ
>
>
>
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