[Elecraft] Re: FM Broadcast Station Interference

[Sverre Holm - LA3ZA]

Could there be some undesired mixer products in the K2? 

Say that the BC signal enters the K2 by radiation after the input LP/BP
filters, and that there is a small 5. harmonic in the oscillator. This
will mix almost perfectly with the broadcast signal. The following
calculation could indicate what goes on based on the K2's IF of 4915
kHz.

Displayed frequency                  14082 kHz
Oscillator frequency: 14082 + 4915 = 18997 kHz
5. harmonic of oscillator            94985 kHz
Mixes with 99.9 MHz to give an IF of  4915 kHz

A bandwidth of +/- 50 KHz for the interference translates to 1/5 in the
setting of the K2 dial, i.e. 14082 +/- 10 kHz which almost takes us down
to your observed worst frequency of 14068 kHz.

A similar calculation near the 40 m band and the 8. harmonic gives 6958
kHz as the worst frequency, and in the 80 m band 3720 kHz and the 11.
harmonic could give this effect. If this is the cause, most likely the
even harmonic effect (40 m) would be weaker than the odd harmonic effect
in the 20 and 80 m bands.


Does this make sense and correspond to anything observed?


73 and good hunt, 
Sverre


Sverre Holm, LA3ZA
Asker, Norway (59.8N, 10.4E)
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www.qsl.net/la3za