[time-nuts] Frequency counter questions

Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Apr 26 17:19:20 EDT 2017

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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