Hello Wolfgang: OK on the very fast spectal analyzers. I will see what I have in the fast department. I do have a medium wave vfo I built here recently for a low powered 100 miliwatt transmitter and I need to run some test on it. I have it down to a drift of only 50 Hz so far, which seems to stop after 45 minutes. But it will give me a chance to see what the spectrum analyzers I have will reveal to me like you were saying. I have found a new circuit idea in the ARRL Handbood for a thermally controled heater to go in vfo's which is an idea I have been studying myself and someone has already come up with a good yet simple design.
The divider chips are basically the J-K Flip Flop circuits (like in frequency counters) and those ones they call "Divide by N types" which are very popular circuits inside the CB phase lock loops. I suppose some are called "binary dividers" and who knows how many names these chips have. I do not know what sort of gates they are; AND, OR, NOT, NAND, etc, its been awhile since I studied them internally wise. And some are simply "clock circuits" which is perhaps the best thing to call them. The Soft Rock 40 uses a frequency divider chip scheme and I am not sure what the chips are that are used, but I could look them up. I did look them up once, and so must look them up again. One thing I realize that concerns me about using a chip that has a TTL square wave signal output from a local clock oscillator is the square wave output itself; which can introduce ripple on the wave form and harmonics as well as phase noise. So your comment on unwanted products from chip ideas is one I share myself. I am not sure if such a signal as this will be ultimately desirable as a local oscillator source to a mixer? I could be wrong about it but it seems like something to investigate or perhaps look up information on. I do want to be able to use DRM as well as other software, so your ideas seem very much what I must look up in the text books. I know that such square wave signals are already being used in the quad circuits I have seen to date and do seem to work very much. Question then is how well do they work and to what degree? I am leaning towards a sine wave input from a local oscillator or vfo to a quad mixer board as the best possible mixing signal. And it seems to me that the purer the sine wave as you seem to indicate with your comments on the lack of noise and jitter, perhaps the better. I mean this seems reasonable but I could be thinking as one said "old analog think." Some single package block type oscillators for fixed frequencies are sold as low phase noise and low jitter types so use of them right off could be the way to go. I would have to look in the manufactures text I have; to see whats what in that regard. That idea may solve folk a lot of problems in some designs they may wish to try. And reduce the need for them to have to build an oscillator since it is all in a single package to plug into the board. (Some of those may also now have crystal ovens built into them, I will check it out and see.) Your reference to multiplying up a 1 Mhz source signal is something I am familiar with. It can give you a lot of frequencies with just one crystal and makes sense in terms of economy. Here is where the source could come from such a pre-manufactured single package oscillator for 1 MHz, rated low on noise and jitter. Anyways I will check out what my spectrum analyzer software can do for me and see if it tells me things about phase noise and jitter. I can see noise from a vfo on the sine wave with my oscilloscope, it adds either ripple or a ghost outline on the sine wave itself. The ghosting effect spells jitter mostly, especially if the sine wave trace itself is wider and appears less focused at the zero axis than near the upper portions of the trace. A sharply defined and clean looking sine wave trace from 0 to 360 degrees spells low noise and very low jitter I believe. You can see jitter when the sweep rate is increased by watching where the trace crosses the zero axis. It will actually jitter back and forth there, or appear less focused than the rest of the wave form. Jitter is in the horizontal plane and does not appear in the upper and lower parts of the wave crest. Only on the most vertical areas of the sine wave. I think I have enough ideas now to crack open the books and start a search of things with. So thanks for the input and I think I have some things now to go on in regard to digital recievers. No doubt you all will give me more info as time goes by. 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/
