Re: Dirty Transmitters

Rob Sherwood

Yes it makes a difference as to the voltage, and voltage drop in some long cables, plus the fuses and holders, can exacerbate the issue.  I set my Astrons at 14.3 volts to compensate for a typical voltage drop of 0.5 volts.  I haven’t seen a night and day difference between 13.8 at the radio and a half to a full volt higher (within the +/- 15% typical spec), but as one goes much lower than 13.8 IMD can measurably degrade.  


I guess the question is what is significant, and would anyone on the receive end notice?  13.8 to 14.3 volts, I doubt it.  At 12.0 volts, maybe so since the degradation might be several dB. (5 dB?) Who knows without an actual measurement on an individual rig.  Of course the IMD varies band by band, and tests in the lab are done into a resistive power attenuator, not an real antenna.


Rob, NC0B 


From: [] On Behalf Of Bob Novas via Groups.Io
Sent: Monday, November 04, 2019 10:54 AM
Subject: Re: [Elecraft-K3] Dirty Transmitters


Is there any difference between 12V and 13.8V or 14.1V, e.g., does it matter if you’re running off a run down battery?  Should you run the voltage up to the max if you’re running on AC?  Just curious if a volt or two makes a significant difference. If it does, maybe it’d be worth running as high a voltage as you can safely. Bob - W3DK


From: [] On Behalf Of Drew Vonada-Smith K3PA
Sent: Monday, November 04, 2019 12:07 PM
Subject: Re: [Elecraft-K3] Dirty Transmitters


The K3 has nice low phase noise, but no SS transmitter running at 12 V has great IMD.  So no, the K3 is not an especially clean TX on SSB.  By no means the worst either, of course.


Drew K3PA

Join to automatically receive all group messages.