I read the digests, so I won't quote all of the helpful responses I've received
on this topic but will add on here.
Let me restate, the K3 was operated without an antenna and just a 50-ohm
termination on the antenna connector. The only other piece of equipment
operating in the shack was the Astron RS35A power supply. I do not have a
second receiver installed. I have only the 2.8 KHz filter installed and all of
these tests were with the default DSP BW. Noise reduction and noise blanking
were off. The preamp was on and does make a difference in strength of the
spurs, although many are heard without the preamp.
Per a suggestion from Tony, K2ZLS, I did a recalibration, which may have
reduced the number of birdies, but certainly did not eliminate them. I have
checked all of the internal cable connections and they are fully engaged.
To be sure, most of these are very low level, but as on old EME op, they are Q5.
Someone wanted some frequencies listed. Here are some, but by no means all of
them, listed by mode in sets that seem to be related and slightly rounded:
F_lsb F_usb F_cw
50.0000 50.0000 50.0000
50.0270 50.0270
50.0313 50.0342 50.0310
50.0400 50.0453 50.0395
50.0473 50.0476 50.0470
50.0750 50.0747 50.0755
50.0793 50.0773
50.0953 50.0933 50.0950
50.0982 50.0988 50.0986
50.1108 50.1108 50.1116
50.1228 50.1228 50.1228
50.1363 50.1303 50.1356
50.1589 50.1588 50.1586
Years ago I built a high-performance HB receiver for 10-meters and i-f for
transverters. For evaluation I also built a test oscillator, like the XG-1
that used a 28.700 MHz crystal. One of my first tests of the K3 was to use
this oscillator to measure sensitivity. By serendipity, the first birdie I
discovered was at 28.700 +/- MHz. Go figure.
Wes N7WS
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