On Sep 30, 7:37*pm, "Joel Koltner"
wrote:
I'm thinking it'd be a rather poor idea to make a reference oscillator for a
DDS (or PLL) equal in frequency to an IF somewhere in your radio... right?
Since you're just asking for it to get into the IF itself?

In the ideal world, would one choose reference oscillator frequencies that
weren't harmonically related to IFs? *I've seen those "IF planning"
spreadsheets (that calculator where mixer spurs are going to fall), and such a
choice seems like a good start.

Thanks,
---Joel Koltner

Joel -
In fact the BFO for your radio is already in the IF bandwidth, and
there probably is some leakage into the IF amp.

For most applications, you don't notice that leakage unless you
wonder why your AGC is kicking in but you aren't hearing anything.

I have found that keeping the BFO out of the IF, especially for a
diode-mixer-level BFO (+7dBm) requires putting the BFO in a box.

I would expect that putting your DDS in a box will help in general.

Tim.