niteviser wrote: > OK Ed, > > I have 2 files showing the PCB details with -26 variant info. They frequency > reference is still kept totally internal. If higher stability or external > reference is available, the internal is removed and a mini coax socket fitted > to have a cable connected to have an input on the rear panel. I will put the > pdf files in the files section. Look for T857 220-01398-02_-04.zip. > > Al (niteviser) >
Al, Thanks for the PDFs. Can you tell me where/how the "FM" (tuning voltage) is brought out on the -26? I looked and both the -02 and -04 variants show the FM pin on the VCXO tied to 2.5V and AC coupled to REF-MOD. For the life of me, I cannot find a DC path that would allow for external frequency shifting. If the -26 still has the resistive divider and nothing else loading the FM pin, just ignoring the tuning voltage path should work fine (as a -20). Other than that, it appears only a few resistor and capacitors are different from a -25 to comply with frequency mask compliance and these would need to be changed anyway to make it a -20. Ed Yoho W6YJ
