Hallo Dan, could be a very interesting information about Your 2 VFOs with PLLs.
I think the problem - generally in radio-circuits - is the more or less fact, that everything seems to be very simpel and straightforward. By exactly experimenting a lot of receivers are not so strong as they should be. But they are very cheap to produce and to distribute and have some advantages, which are really new, as showing precise digital frequencies at the receiver. On the other hand: All of this so called modern and little and most handy stuff, is not so nice as it could be - I think. To a certain extent it is an advantage. If You hear the first time a disturbing signal coming from Your just newly bought receiver, You are somewhat alarmed. And sometimes a lot of more factors, You will find. On the other hand. Nobody is really able to hear by a Barlow Wadley XCR30 receiver, which I like much. They are based on a quartz-oszialltor, which is stable. It is working on 1 Mhz and mixes the first VFO with its mixed mulitples of its own basis. Because of that, this receiver is extremly stable in its first oscillator. Mainly they seem to be torn out and should be in some parts reconstructed. 2 months ago, I heard a superhet-receiver from the late 30s, a german before war design. It was reconstructed by Ulf Schneider and its perfromance is extremly well. Knowing this, one is asking, what did all these constructors for decades in designing radios. Except installing transistors and ics instead of valves and miniaturisation. They only thing missing is a digital frequency display. Never the less: What one has not experimented would not be a fruitfull information. I think all these warnings about unreliable VFOs with PLL could be a fundamental problem of these modern very smart and cheap receivers. And especially in HF-design, one has not so much competitors. My picture of working in receiver design offices is choosing the right chips to the right prices. The result should be investigated by freaks, which could just be normal people - to a certain extent-. I have the overall experience, that modern technique could even bring a qualified success even for AM, SSB and other modulation-types. This for the moment Wolfgang --- In [email protected], "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > > 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/
