Wolfgang: Earlier In the emails I mentioned dual pll locked vfo's I have in a 1972 era receiver here and I have the circuit diagrams I want to draw up on the PC here and give to the group.
I will explain the idea here a little. Both vfo's are all transitorized and both are pll locked, the pll circuit is transistor also and there really aren't allot of parts to the them. Two crystals, a vco coil, three transistors or so to the loop, a varicap diode, etc. One vfo is the main bandspread tuning vfo and it locks every 100 kHz and the fine tuning vfo only tunes 100 khz of the band portion selected by the main tuning vfo. The fine tuning dial is graduated to a resolution of 250 Hz but tuning is way finer than that even. (There is a bfo that helps to locate the signals edge when tuned in usb or lsb mode.) I do not seem to have trouble with the stability on DRM or when I use it to tune to BPSK signals. When using something like Spectran or other spectrum display software such a Ham Scope (for digital modes such as BPSK) I do not notice any drift whatsoever on the water fall displays at high resolution during reception of digital modes. All of the circuits are individually contained in their own sheilded box. It is sort of the ultimate receiver like you would see in the ARRL publications all sheilded, etc. Things I have noticed about the construction of the vfo's is that both use tuning capacitors with large spacing between the plates and the plates are fairly thick and rigged. I feel that this allows more dissipation and makes it also mechnically strong and much harder to expand when made warm. The main tuning coils are on ceramic cores with ferrite slugs. Being simple in construction is also an advantage cost wise and the tuning of the vco's or the loop isn't hard. The circuit diagrams I have also have the expected oscilloscope waveform photos also. All of the tuning and alignment data is in the text also. Anyways, I believe that from the numerous pll controled vfo circuits I have seen that the best one I can recommend is the one in my receiver and I will draw it up when I can and give the text to anyone how might like to check it out. When I get the time I will draw up both circuits and put them in a single PDF file and make them available to anyone interested in such circuits. Dan _____________________________________________________________________ Call Anyone, Anytime, Anywhere in the World - FREE! Free Internet calling from NetZero Voice Visit http://www.netzerovoice.com today! Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
