Jerry,
I would not advise connecting the Softrock without isolation in any case
- I believe the biggest problem is that the Softrock LO signal can be
coupled back into the K3 and can cause spurs on the *transmitted*
signal. This is one you cannot evaluate with the K3 receive. A
spectrum analyzer at the K3 output would be required for a good
investigation of your question. On receive, the normal K3 filters and
the DSP may be quite able to reject the Softrock LO signal.
Take a look at Larry Phipps website www.telepostinc.com for his LP-PAN
project. Larry has measured the LO of the Softrock at -40 dBm which is
an S9+30 signal. I do not think one would want to inject such a strong
signal into the K3 IF - at least 20 dB of isolation is needed.
73,
Don W3FPR
Jerry Flanders wrote:
Hi, Jo
Did you have to get the KXV3 before using it with the K3, or did you
find another way to interface the softrock to the K3?
Since the K3 roofing filters (centered at 8215) do not pass much of
your LO freq of 8204 KHz, I am guessing that you would not have seen
much effect of the moderately weak LO signal at all in the K3 - did
you try it before you added the additional isolation stage?
Jerry W4UK
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