Re: [K2] Spurious emission in SSB
Posted by
Elecraft mailing list on
Aug 31, 2020; 12:31pm
URL: http://elecraft.85.s1.nabble.com/K2-Spurious-emission-in-SSB-tp7664521p7664533.html
Chris
Is the frequency separation exactly 900 kHz? If a bit more, perhaps the oscillator in the KSB2 MCU (U1/Z1) at (nominally) 4 MHz is coupling into the IF (nominally 4.915 MHz) path on the same board, on the output side of the crystal filter). Problems with grounding, bypass capacitors and long leads might do this. I have a vague recollection that the instructions for early KSB2 board assembly did not involve grounding the filter crystal cases and later instructions did. That shouldn't directly affect that coupling but it might generally help provide a generally more solid ground.
There are other 4 MHz oscillators in the K2 that might couple in, too, but since the problem only exists on SSB, it seems this one would be a more likely culprit.
Could re-aligning the 10 metre bandpass filter (K2 RF Board) help?
Generic ITU Radio Regulations require -43 dB dBc or better spurious levels at 1 watt output, so one hopes it could meet that. Of course if you are running a couple of hundred watts for 23 cm EME, you are required to do better! Of course, you could get 3 dB better signal-to-spurious level just by going up to 2 watts.
I use a K2 (with an internally mounted 2 m transverter) in my 10 GHz setup....I suppose I ought to check for that issue, if I can borrow a spectrum analyzer. But then...who would actually hear me, or have a problem with, a mW level signal at 10.3672 GHz and a beamwidth of 3 degrees?
73,
Steve VE3SMA
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