Re: using P3 and Skimmer

Posted by Don Wilhelm-4 on Aug 29, 2011; 1:05am
URL: http://elecraft.85.s1.nabble.com/using-P3-and-Skimmer-tp6735739p6736072.html

Jack,

Thanks for that information.
I was not thinking about the P3 display.  Harmful injection into the K3
would be no problem because it has a buffered output IF output, but you
are correct, the Softrock LO will produce a spur on the P3 display even
if it does not get into the K3 IF.

73,
Don W3FPR

On 8/28/2011 8:42 PM, Jack Smith wrote:

> Don:
>
> I recently had a question from a prospective customer for a Z10000B
> buffer amplifier about the need for additional isolation if a Softrock
> is used with the P3's splitter IF output.
>
> I can't find a spec for the P3's isolation between the IF output port
> and the IF Input, but 30 dB isn't a bad estimate for a 3 dB  hybrid
> splitter.
>
> Typical local oscillator leakage out of a Softrock is -40 dBm, so a -70
> dBm signal (approximately) will be injected into the P3's input if a
> Softrock is connected to the P3's IF out port. This will appear as a
> spurious pip on the P3's display at around -70 dBm.
>
> The LPPan has isolation and it's leakage is not a problem when used in
> this fashion.  But, I believe a Softrock will require additional
> isolation, on the order of 60 dB or so, in order to be useful without
> injecting a spurious pip into the P3.
>
> Jack K8ZOA
>
>
>

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