[600MRG] Power Supply Discussion

[Larry Molitor]

Any "clicks" caused by the rather slow decay of the power supply voltage are lost in the noise created by the junk created by the crappy class D/E amps.
The only reason they are tolerated (so far) is that
#1 The population density on these bands is so low nobody is bothered.
#2 Nobody uses high speed CW. The relatively infrequent transitions occurring in WSPR/JT9 and QRSS transmissions are lost in the overall QRN.
And BTW, all the waveforms generated by any K1JT software is well shaped and causes little or no spectrum disturbances. Any clicks observed are the result of crappy TX and amps.

If you or anyone else was truly worried about clicks and other crap, you wouldn't be messing around with non-linear amps. If these bands ever get populated as much as, for instance 40m, class D/E amp users will be run outa town on a rail (so to speak).
In any case, the worst issue with class D/E is the spurs caused by poor power supply filtering.
Larry - W7IUV / WH2XGP      From: Frank Lotito <k3dz at live.com>
 To: 600 / 630 Meter Group <600mrg at w7ekb.com> 
 Sent: Monday, February 27, 2017 10:01 AM
 Subject: [600MRG] Power Supply Discussion
   
A recent post regarding power supply designs for nonlinear MF and LF power amplifiers suggested a brute force unregulated design.  Most definitely, I agree, for continuous carrier type emissions.  What about key clicks when the carrier has to be keyed, such as regular old fashion CW?  Or for that matter QRSS keying, if you would, the start / stop of a WSPR or JT9 transmission, the start / stop of a dit or dah in QRSS transmission?  I submit that if the brute force supply's internal resistance is not "very-very low," there will be a substantial click on make / break.  How would you sufficiently suppress the key clicks for such a power supply approach if there might be a power supply droop of 20 percent or more?  How do you get a very-very low power supply droop?  It might be a little more involved than using "large bore" components for modest power delivery.


I think the key question is "Does power supply droop instigate spurious oscillations?"  If yes, can the power supply droop be combatted with driver keying?  As a means to minimize keying clicks my gut feeling says driver keying may not do it.  As I understand, if the driver keying spends to much time making the transition from hard turn on to hard turn off (and visa versa) there is an increased risk of spurious oscillations while the amplifier is making this transition.


I use a regulated DC power supply, but key the Vcc line going to the my non-linear RF power amplifier using a series P-channel power mosfet.  It took a while for me to work out a means to key the mosfet's gate to get an acceptable rise / fall time of my KB5NJD / WG2XIQ designed amplifier.  I am still not 100% sure that in the on / off keying transition I am not generating spurious oscillations.


Suggestions?  Comments?


73 Frank K3DZ / WH2XHA
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