[Elecraft] Observation on new Synthesizers for K3

[Alan]

On 07/08/2015 06:02 AM, David Cole wrote:
>
> It occurs to me that the the the RX VFO phase noise would be less
> influencing, (on phase noise sidebands), than the transmit VFO phase
> noise...  Is that correct?
>
> If so, then that would explain why the largest change occurred when
> K7OLN got his new synthesizer, as opposed to me getting my new
> synthesizer, as shown in the difference between photos 2 and 3.
>

I believe the TX and RX phase noise have an equal effect on the 
interference.

Let's say the phase noise of the new synthesizer is 10 dB better than 
the old at a particular offset frequency.  That is, 1/10 the power.

If you replace one synthesizer (RX or TX) then the total phase noise is 
reduced by a factor (1 + 1/10) / (1 + 1) = 0.55 or -2.6 dB.

If you replace both synthesizers, then the total phase noise is reduced 
by a factor (1/10 + 1/10) / (1 + 1) = -10 dB.

I don't think it makes any difference which synthesizer is changed first.

Alan N1AL