[time-nuts] Basic question regarding comparing two frequencies

J. L. Trantham jltran at att.net
Sat Jul 24 16:49:51 EDT 2010

Sounds about right.  One cycle per 5 seconds or about 0.2 Hz difference.
Therefore, 9,999,999.8 Hz.

I would feed the GPSDO to trigger your scope and look at the output of the
time base on one channel of the scope.  You could also look at the GPSDO on
the other channel.  Then you could adjust your counter time base to 'freeze'
the display.  Probably good to 'align' the counter time base but for long
term comparison, probably better to use a counter and plot the difference.


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Mark Spencer
Sent: Saturday, July 24, 2010 12:29 PM
To: time-nuts at febo.com
Subject: [time-nuts] Basic question regarding comparing two frequencies


Just for grins I decided to compare the frquency from my GPSDO to the time
in my 5328A counter.    

I connected the 10 mhz time base from the counter to channel A of my 100 Mhz

scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T
also fed this signal into the input of the counter.    I scope to trigger
Channel B.   

The drift betwen the two signals on the scope seems to match the error in
displayed frquency on the counter.  (ie. if the counter shows 9999.9998 it
approx 5 seconds for the the wave form on channel A to slip a full cycle 
realitve to channel B.)   

Is this a reasonable approach or is there a better way to compare two 
frequencies using a scope ?

Best regards
Mark Spencer

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