one of the inherent problems with 10 MHz if is that it precludes the 10
MHz band. the IF will fall within the RF passband.
it might work if you used 14.318 MHz crystals for IF and used the 4 MHz
vfo to mix down to 10MHz IF.
You have to keep the IF, RF and VFO frequencies away from each other as
well as see to it their various (and particularly odd) multiples don't
match up.
For instance, you used a 9Mhz IF for an 18 MHz design. The second harmonic
of the BFO will appear as a tunable signal in the receiver. The VFO will
also appear as a quickly tuned spur.
W7ZOI has a program called spurtune.exe that is ideal to work these spur
resposnes out.
i am not sure about the copyrights on these programs. if they are
distributable, then i can upload them to our folders for everybody to use
them. they are very useful, all of them.
- farhan
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On Sat, 3 Jul 2004, MILAREPA wrote:
Dear Forum,
Suppose I plan to have some band selection in future, after 'original' 14 MHz has been set up.
I just need confirmation about my frequency 'plan' table below,
is this correct in the meaning of 'practical' especially for 10 MHz,
that the VFO need to tune 0 ~ 0.4 MHz ?
Thanks.
