It's a remarkable, and largely unappreciated, instrument. I passed them up for years, thinking they were only useful for analog multiplex telephony. It was not until I bought one, almost by accident, at the tail end of a flea and started to play with it, did its utility became apparent. Thje ability to lock onto a received carrier and count it is a delight, IMO.
A note on the data you get out. If you digitally high pass filter it, you should be able to get a measure of the path stability. I've done this with both an HP 117A on WWVB and WWV but not yet with the 3586C. The day-to-day variation is dramatic. Best, -John ============ > I like the 3586 a lot, it's amazing what you can do with it. However, if > you send the audio (beat note) to a computer or other instrument, keep in > mind that the BFOs are not phase locked to the reference, they are just > free standing crystal oscillators, and they may be off by a few Hz. If you > want to use the beat note for high accuracy frequency measurement, it > would be a good idea to phase lock the BFOs to the reference (at least the > one you are going to use, you don't need to do both). > > The carrier frequency measurement system is independant of the BFOs. > > Didier KO4BB > ------------------------ > Sent from my BlackBerry Wireless thingy while I do other things... > > -----Original Message----- > From: "J. Forster" <j...@quik.com> > Sender: time-nuts-boun...@febo.com > Date: Mon, 26 Jul 2010 14:23:02 > To: Discussion of precise time and frequency > measurement<time-nuts@febo.com> > Reply-To: j...@quik.com, Discussion of precise time and frequency > measurement > <time-nuts@febo.com> > Subject: Re: [time-nuts] Basic question regarding comparing two > frequencies > > What about using an HP 3586 B or C, locked to a local standard, and GPIB > interface and averaging the data? It goes to 0.1 Hz right out of the box > as I remember. > > FWIW, > > -John > > ============= > > >> Hi >> >> Rather than having the 940 in there, why not just build a (simple) >> direct >> conversion receiver? >> >> Feed something like the 3335 or 6061 into one port of a suitable mixer. >> Feed >> the band pass filtered signal from the antenna into another port. Run >> the >> IF >> output into a preamp / filter and then into the sound card. >> >> You'll get DSB down to the audio chain, but that can be fixed with more >> hardware. Often it's a non-issue. It all depends on what sort of signal >> you >> are after. >> >> Another idea: >> >> Butcher the sound card and feed it a synthesized clock that's locked to >> the >> z3816. One less step in the data reduction / one less thing to worry >> about. >> The sound card *might* even run off of one of the outputs the z3816 >> already >> generates. You'd have an odd sample rate, but that's not a big deal. >> >> A comment: >> >> Cleaner is always going to be better on the RF generator that is your >> ultimate reference. Anything you can do to improve close in phase noise >> will >> likely help things out. >> >> Lots of possibilities. >> >> Bob >> >> >> >> -----Original Message----- >> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On >> Behalf Of Guy Lewis >> Sent: Monday, July 26, 2010 4:51 PM >> To: 'Discussion of precise time and frequency measurement' >> Subject: Re: [time-nuts] Basic question regarding comparing two >> frequencies >> >> >> >> -----Original Message----- >>>> There is another way to compare two frequencies, relevant when they >>>> are >>>> very close together................... >> ------------------------------------- >> I am trying to measure the frequency of a distant on-air signal, with >> path >> fading, Doppler shift, and maybe even AM modulation and would appreciate >> comments that might improve accuracy to better than .01Hz. The idea is >> to >> measure the frequency of an audio beat between a disciplined synthesized >> generator and the on-air signal, the subtract out the difference. Here >> is >> what I am doing: >> >> Equipment: >> GPS Disciplined Oscillator (HP 3816A with antenna) >> Synthesized generator with .001Hz resolution (HP3335A locked to GPS 10 >> MHz >> reference) >> PC running Spectrum Lab sound card audio spectrum analyzer software >> Second locked synthesizer (Fluke 6061A) to determine Spectrum Lab >> frequency >> error >> AM receiver (TS940 for 30kHz to 30 MHz) and antenna covering unknown >> frequency to be measured >> Input signal combiner (Merrimac 50 ohm combiner) or leak into receiver >> across Ext Rx switch >> >> Setup: >> 1a. Disable TS940 transmit mode (power set to minimum, PTT disabled, >> don't >> touch SEND) >> Install power splitter at Rx input to mix unknown and synthesized >> generator >> signals >> --or:-- >> 1b. (preferred alternative, to avoid accidently transmitting into the >> generator), leak generator signal into TS940 across Rx antenna switch at >> a >> higher level >> 2. Lock generator to external GPSDO. All OCXOs run full time >> 3. Connect audio out to PC running Spectrum Lab >> 4. Allow PC to warm up for at least 30 minutes and measure second locked >> synthesized generator near the expected unknown frequency to determine >> Spectrum Lab measurement error >> >> Measurement of unknown signal frequency: >> 1. Set Rx to approximate frequency of unknown signal, AM mode >> 2. Adjust generator to create a clean audio beat note (power, freq + 600 >> Hz >> audio freq, narrow AM filter) >> 3. Be sure clockwise rotation of generator frequency knob increases >> audio >> beat note frequency. Tune generator to upper side of signal if necessary >> 4. Read peak audio frequency from Spectrum Lab display >> 5. Subtract audio frequency (Spectrum Lab reading -measured .046 Hz >> error) >> from generator dial reading for result. >> >> Example measuring WWV @ 10 MHz: >> >> Rx tuned to 10 MHz, AM mode, Narrow Filter >> Antenna signal mixed with -70 dbm (-30dbm if leaked across Rx switch) >> generator signal. Adjust level for cleanest audio tone. >> Generator frequency tuned to generate 600 Hz beat note reading in >> Spectrum >> Lab >> Generator frequency reads 10.000599954 >> Audio frequency increases as generator frequency is increased >> Spectrum Lab reads audio frequency 600.00 Hz >> Spectrum Lab frequency readout error known to be .046 Hz high (actual >> audio >> frequency is 599.954Hz) >> >> Calculation: >> Unknown freq = Fgen-(Fspeclab-Fspeclaberr) >> WWV freq = 10,000,599.954Hz-(600-.046Hz) = 10,000,000.000Hz +/-.01Hz >> >> Any suggestions appreciated. >> >> Guy >> N2GL > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.