[time-nuts] HP 5372A

Magnus Danielson magnus at rubidium.dyndns.org
Fri May 11 15:12:38 EDT 2018


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.

> 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



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