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

[Tim O'Rourke]

Tom
I have not seen or heard this in my setup, I am using Gerd's T/R board driving his Hercules Amp. I do not see it in panadaptor display or hear it. I have never had Penny hang in tx either. 
Tim W4YN


-----Original Message-----
>From: Tom Cathey <k1jj at comcast.net>
>Sent: Feb 1, 2011 9:44 PM
>To: hpsdr at lists.openhpsdr.org
>Subject: [hpsdr] Penny PTT unkeying spike - T/R sequencing?
>
>***** 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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Tim O'Rourke 
W4YN at ARRL.Net
Low Power Amateur Radio Rocks 
Member of Flying Pigs,ARCI,GQRP,RSGB,ARRL Life Member
NHRA Life Member

 1296663148.0