[Elecraft] using P3 and Skimmer

[Larry Phipps]

Correct Jack. Just a couple additional comments...

LP-PAN has more than enough isolation, but we recommend the optional 
preamp (mounts inside LP-PAN) to overcome the total losses of the K3 
buffer and the hybrid splitter in the P3.

FWIW, I have measured the isolation of the P3 splitter, and it is 
considerably lower than 30dB. If using a SoftRock, I would consider it 
imperative to use a Z10000 or similar buffer. It would also make sense 
to use one of your low noise preamps ahead of the Z10000 if weak signal 
decoding in CW Skimmer is important. I would set the gain of the preamp 
at about 10dB, and the buffer at about 0dB.

73,
Larry N8LP


On 8/29/2011 12:00 PM, elecraft-request at mailman.qth.net wrote:
> Date: Sun, 28 Aug 2011 20:42:04 -0400
> From: Jack Smith<jack.smith at cliftonlaboratories.com>
> Subject: Re: [Elecraft] using P3 and Skimmer
> To:elecraft at mailman.qth.net
> Message-ID:<4E5AE05C.1020004 at cliftonlaboratories.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> 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
>