[Elecraft] K2 #6593 Transmit Performance

[Don Wilhelm]

Merlin,

Please define "noisy" so we can have a better understanding of what is 
happening.
If you have a selective receiver available you can scan the spectrum on 
each side of the signal for about 1 kHz and gain the same information as 
with a narrow band spectrum analyzer.  Another method is to use a DC 
receiver and look at the audio output of that DC receiver with 
Spectrogram to view up to 6 kHz of the spectrum at the signal frequency.
Are you certain it is not your receiver's response with a short antenna 
attached?
Although the source could be anywhere in the transmit chain (or even 
outside the K2 as you hinted (power supply maybe?) - there are 3 main 
areas I would look first, BFO, VCO and transmit mixer.

73,
Don W3FPR

m0trx wrote:
> Dear All,
>
> I recently finished building K2 #6593 and have been thoroughly impressed
> with the performance of the receiver. However, having done some initial
> tests on transmit into a dummy load, whilst monitoring the signal on another
> receiver, I have noticed that the the signal starts to sound noisy as the
> frequency is increased (i.e. 40m sounds clean but 10m sounds far from
> clean). I do not currently have access to a spectrum analyser in order to
> check this quantitatively.
>
> The K2 is located far from my linear power supply (at least 3-4 feet) so I
> doubt this is due to modulation of the VCO from the 50Hz supply. If this
> were the case then the problem would be prevalent on all bands anyway. I
> wonder whether anyone could shed some light on the likely cause of this. I
> am beginning to wonder whether the frequency components I am hearing are
> actually on the transmitted signal or as a result of some mains coupling.
> The reason I think this is because the level of said frequency components
> relative to the carrier is higher on one receiver than on another (both in
> same room, aerial etc).
>
> Any commnets would be most welcome.
>
> Regards,
>
> Merlin Cooper
> M0TRX
>   
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