[time-nuts] Frequency counter questions
jerry at hanler.com
Wed Apr 26 19:17:29 EDT 2017
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.
> 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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