[time-nuts] Frequency counter questions

[jerry]

I can measure to .001hz using my scope.  I thought I mentioned that the other day?  It depends on frequency and how much time you want to wait, I think the low frequencies take a lot longer to stabilize.




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-------- Original message --------
From: Bruce Griffiths <bruce.griffiths at xtra.co.nz> 
Date: 4/26/2017  2:19 PM  (GMT-08:00) 
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>, al wolfe <alw.k9si at gmail.com> 
Subject: Re: [time-nuts] Frequency counter questions 

Use a USB or LSB mixer, it only requires a few more parts and a little ingenuity.

Bruce

> 
>     On 27 April 2017 at 06:52 al wolfe <alw.k9si at gmail.com> wrote:
> 
>     I am surprised that no one has mentioned the idea of heterodyning a
>     known frequency with the unknown to measure the unknown. I use a
>     Minicircuits doubly balanced mixer fed on one port from a PTS160
>     synthesizer that is locked to 10 mhz. from a TrueTime xl-ak GPS locked
>     receiver. The second port is fed by the unknown though an attenuator.
>     The third port of the mixer gives me the sum and difference. If the
>     difference is an audio note then a cheep but frequency locked counter
>     will read out the difference or measure the period of the beat note
>     which can be added to the frequency of the synthesizer. A program such
>     as Lady Heather can also be used to determine the audio frequency to
>     much less then sub-cycle accuracy. The only fly in the ointment is
>     figuring out which side of the unknown the synthesizer is set to.
> 
>     Alternatively, the PTS160 with 0.1 cycle control can be set to nearly
>     zero beat with the unknown. Then watching either lissajous or dual
>     trace scope patterns and timing the beat notes one can get the unknown
>     frequency very close.
> 
>     Al, retired, mostly
>     AKA k9si
> 
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