[Elecraft] Phase noise suggestions

[Stewart Baker]

This topic runs and runs with no obvious solution. It should be possible to 
bread board the affected area of the K2, make measurements, and work out 
corrective action. It may be easier to analyse the results of any mods by using 
a received signal than a transmitted one. Here is a post 'that I made earlier'

73
Stewart G3RXQ
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The problem of a power transformer close to a K2 such as to cause problems on 
SSB has oft been reported. What I have not seen so far, is, that because it is 
the PLL  that is affected the problem can also be observed on receive.

Instead of transmitting a "gungy" signal, asking for reports,  moving the PSU 
or K2 around and repeating the process, I used the following procedure on 
receive:-

I ran SpectroGram with my soundcard connected to the K2 loudspeaker socket.
A strong unmodulated carrier (XG1 set to 50uV) was applied to the ANT input.

It is necessary to get the smallest  frequency resolution (5.4Hz) on 
SpectroGram so set the Scan Input (F3) to these settings :-

Sample Rate 11kHz
Resolution 16bits
Scale 60dB
Freq Scale Linear
FFT Size 2048
Average 70

 Using either the SSB or CW filters tune in the signal until an audio signal of 
800Hz to 1kHz is obtained, and adjust the displayed signal amplitude to around 
0dB. The noise floor in the filter is approx -60dB.

Any modulation of the K2 PLL will now appear as sidebands to the main signal.
They will be spaced at either 50Hz (Europe) or 60Hz. If the problem is intense 
there may be harmonics. Switch PSU's On/Off to confirm (Not the K2 one !)

A small homebrew PSU in a diecast box placed 12in away from my K2 gave 
sidebands of -40dB. I dread to think what the field from a high power linear 
amplifier could produce.
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