[time-nuts] Frequency counter questions

EWKehren at aol.com EWKehren at aol.com
Wed Apr 26 19:10:36 EDT 2017


We do it and get at 1 sec 1 E-13 resolution and 1 E-12 accuracy for the  
work we do. 
Bert Kehren
 
 
In a message dated 4/26/2017 3:00:54 P.M. Eastern Daylight Time,  
alw.k9si at gmail.com writes:

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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