[600MRG] Power Supply Discussion

[Frank Lotito]

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