[time-nuts] Basic question regarding comparing two frequencies

Didier Juges didier at cox.net
Sat Jul 24 21:54:57 EDT 2010


Check
http://www.ko4bb.com/Test_Equipment/GPIB.php

Didier KO4BB

------------------------ 
Sent from my BlackBerry Wireless thingy while I do other things...

-----Original Message-----
From: Mark Spencer <mspencer12345 at yahoo.ca>
Sender: time-nuts-bounces at febo.com
Date: Sat, 24 Jul 2010 18:15:20 
To: <time-nuts at febo.com>; <jfor at quik.com>
Reply-To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] Basic question regarding comparing two frequencies

Thanks for the insight re the GPIB interface.  I'm curious if any has any insight as to a suitable usb or pci to GPIB interface module or card ?  It sounds as though other surplus test gear is likely to have a GPIB interface.  Regards

Mark Spencer

On Sat Jul 24th, 2010 6:40 PM EDT J. L. Trantham wrote:

>I would agree. GPIB (aka HPIB) is ubiquitous and is a great place to start.
>Unfortunately, I haven't gotten that up to the top of my 'to-do' list yet.
>I have a computer, HP and National interface cards, cables, but no time to
>find the software to make everything communicate yet.  I think it has a lot
>to do with the fact that I have relatively old HP equipment that is
>relatively 'tongue-tied' but I think I will be able to figure it out once I
>get the time.
>
>Certainly the right place to start though, IMO.
>
>Joe
>
>-----Original Message-----
>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>Behalf Of J. Forster
>Sent: Saturday, July 24, 2010 5:24 PM
>To: Discussion of precise time and frequency measurement
>Subject: Re: [time-nuts] Basic question regarding comparing two frequencies
>
>"..  more generic interface." ??
>
>The vast majority of professional test equipment has GPIB. Virtually
>anything else is an "also ran".
>
>FWIW,
>
>-John
>
>============
>
>
>> Thanks, I'm glad to hear I am on the right track.   At some point it would
>> be
>> nice to obtain a counter that can measure the drift of the time base in
>> the
>> 5328A.  The 5328A has a GPIB interface but as the display only varies by a
>> few
>> counts I'm not inclined to track down a GPIB adapter just to plot this.)  
>> Hopefully a newer counter would have a more generic interface.
>>
>> Best regards
>> Mark Spencer
>>
>>
>> ----- Original Message ----
>> From: J. L. Trantham <jltran at att.net>
>> To: Discussion of precise time and frequency measurement
>> <time-nuts at febo.com>
>> Sent: Sat, July 24, 2010 1:49:51 PM
>> Subject: Re: [time-nuts] Basic question regarding comparing two
>> frequencies
>>
>> 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.
>>
>> Joe
>>
>> -----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
>>
>> Hello:
>>
>> Just for grins I decided to compare the frquency from my GPSDO to the time
>> base
>> 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
>> adaptor
>> also fed this signal into the input of the counter.    I scope to trigger
>> from
>> Channel B.  
>>
>>
>> The drift betwen the two signals on the scope seems to match the error in
>> the
>> displayed frquency on the counter.  (ie. if the counter shows 9999.9998 it
>> takes
>> 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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>
>
>
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