HI > On May 11, 2018, at 3:12 PM, Magnus Danielson <[email protected]> > wrote: > > Hi Don, > > On 05/10/2018 02:59 PM, Don Murray via time-nuts wrote: >> Hi Magnus... >> >> >> Appreciate any help! >> >> I participate in the ARRL Frequency Measuring Test, >> and I would like to automate the measuring process. >> >> I have two frequencies, A and B... >> >> A is a GPS locked HP 3336B set to 455,000.000 Hz >> >> I use the 3336B instead of the 455,000Hz BFO >> signal from my GPS locked Racal receiver so >> that I can measure AM stations without the >> annoying beat note. ;-) >> >> B is an IF signal which should appear between >> 455,000.000Hz and 455,001.000 Hz >> >> I would like the 5372A to calculate the B minus A >> delta, over a manually started and automatically >> stopped measurement period of 110 seconds. >> >> I would like a delta resolution of 0.001Hz to be >> developed by the box. > > There is no point in using two channels and a generator. > You can do that straight out of the box just by locking it to the GPS, > which you should do anyway. > > Just measure the signal. Using the Math you can subtract or add whatever > frequency you want. You can get A-B or B-A measures in Frequency mode, > it's just not necessary. > > Now, you want to use the single-shot run mode. > > It should be relative trivial to setup a large number of samples with a > suitable distance inbetween them. > > Getting 1 mHz resolution isn't too hard that way, considering you have > 110 s of time to do it. > >> Now, there will be doppler. I want the box >> to analyze and give me a best statistical guess >> for the B minus A delta. > > Now, doppler is tricky, as the HP5372A in all its glory does not have > built-in compensation for it, and besides, you need to figure out where > the true zero is. > > What the box will give you is a frequency estimation assuming doppler > free conditions. If you want to do smarter things, you need to pull the > data off the counter in binary form and post-process it yourself. The > programmers manual for the HP5372A is a great teaching tool for how > these beasts process stuff. > >> BTW the B minus A delta will be added to the >> frequency of my Racal receiver to give me the >> best "guess" as to the correct frequency of the >> target signal. > > For sure. This is BTW something you can do in the Math part of the > HP5372A, so you can have it crunch out the right value straight out. > >> The Racal reads out to the Hz, and I am able to >> accurately determine if the Racal is tuned above >> or below the "target" frequency. >> >> I will be tuned below the "target" and within >> 1 Hz of the "target." >> >> I assume I will be in the one frequency mode. >> >> Can the box give me the desired resolution? > > Sure, assuming the doppler limitation. > >> What sampling period would be the best to use? > > Use one short enough to get as many sample points over the 110 s you want.
The 110 seconds is the big gotcha here. What you really want is a unified record of the entire time they are transmitting. If it’s less than 2 minutes, you are fine. If it runs for 5, 10 or 15 minutes that’s not quite so good. Stitching data together gets you back to binary dumps and a lot of post processing. Once you do that, there really is no advantage over a SDR running on the same signal. Bob > >> What statistical result would I use as my delta? > > Mean value on the Statistics display. It's a linear regression result, > which has good processing gain for frequency. > >> Appreciate your help. My head is spinning whenever I >> get into the operating manual! > > It's a beast, for sure. It took some time to master, but it's a lovely > tool when you understand it and accept it's up-front complexity. > > I could maybe take mine for a test-spin somewhat later. > > Cheers, > Magnus > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
