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Raj,

Very cool that you found such an easy and cheap solution!
Though not so sure I was a part of it in any way.

So that 2.5mhz thing had nothing to do with the si5351, was caused by feedback from the power amp?
Very curious.? I have no idea how that 2.5mhz factor came about.

The extra 45mhz filter would solve the power amp feedback issue.
That was probably all the low frequency rumble in Warren's plots of a few weeks ago.
This would not be fixed by a LPF.

I had assumed that the 45mhz-DialFreq spur was generated inside the mixer at D1,D2.
But apparently the IF amp at Q20,21,22 was generating enough of a second harmonic?
that the resultant 90mhz energy minus the clk2 VFO was going straight on through
the mixer in the expected manner.? As Henning has stated previously.

I'm sure termination impedances around the new filter could be an issue somehow.
But if it works, I'm ok with that!
Passband ripple might not be much of an issue, as the filter is much wider than what we actually use.
Extra insertion loss may not be much of an issue either, especially with the crystal only in
the TX path since we have gain to burn there.? Less TX signal into the D1,D2 mixer is a good thing.

Good job!

Jerry, KE7ER