27-05-2011, 10:18 PM
Conceptually, yes, it is possible. I did just that many, many years ago during the early, formative years of A.M. of 2m; 'tuning high to low', etc. I may well have the cct. of what I used somewhere, buried in the archive of archives! 
Anyway, the leading initial question I have to ask is:
Does this Tx. use a scheme of frequency multipliers from the crystal osc. freq. up to the RFPA?
For example, with an 8 MHz crystal in a 144 MHz Tx., it was customary to use a series of freq. multipliers to produce an overall multiplication of 18, since 8 MHz X 18 = 144 MHz. So 8.111 MHz produced 146 MHz. Hence, a VFO tuning 8.000 to 8.111 MHz was all that was required.
Of course, issues of stability & drive level are relevant at this point - but that's another issue - for now, anyway.
Al.
Anyway, the leading initial question I have to ask is:
Does this Tx. use a scheme of frequency multipliers from the crystal osc. freq. up to the RFPA?
For example, with an 8 MHz crystal in a 144 MHz Tx., it was customary to use a series of freq. multipliers to produce an overall multiplication of 18, since 8 MHz X 18 = 144 MHz. So 8.111 MHz produced 146 MHz. Hence, a VFO tuning 8.000 to 8.111 MHz was all that was required.
Of course, issues of stability & drive level are relevant at this point - but that's another issue - for now, anyway.
Al.
