[time-nuts] Buffering the 1pps output from a Z3801A

Jeff Mock jeff at mock.com
Wed Mar 26 13:19:53 EDT 2008


That's a cool box, but I took a more quick and dirty approach that has 
served me well.  There's a TTL level PPS inside the box, if I remember 
correctly the part has quite a lot of drive and is fine for driving a 
50-ohm cable.  I needed a proper UTC PPS signal for a radio astronomy 
project and I made the following mod to my z3801a:

    solder a 50-ohm resistor to the TTL PPS signal inside the Z3801A.

    Use a nibbler tool to widen a cooling hole enough for a piece of
    rg-58.

    Zip tie a short piece of rg-58 coax into the hole in the side
    of the box.  I have a female connector dangling outside the box.

    Wire the coax to ground and the 50-ohm resistor of the TTL drive.

This has served me well for many years and driven a variety
of spectrometers.  The signal looks great on a scope when terminated
to 50-ohms, but it is a bit of a quick and dirty solution that might
not be appealing to some.

I can't tell you which chip/pin is the PPS signal, it was several years
ago. I'll remove the lid and tell you the proper pin if you take this
approach.

jeff


John Franke wrote:
> See;  http://www.realhamradio.com/sidecar.htm
> 
> John WA4WDL
> 
> ----- Original Message ----- 
> From: "Peter Vince" <pvince at theiet.org>
> To: <time-nuts at febo.com>
> Sent: Wednesday, March 26, 2008 9:29 AM
> Subject: [time-nuts] Buffering the 1pps output from a Z3801A
> 
> 
>> Bruce, et al,
>>
>> The 1pps output of an HP Z3801A and Trimble Thunderbolt is
>> only available (as far as I know) as a balanced ECL signal on the
>> 25-pin connector, with dire warnings in the manuals about not
>> earthing either side of the ECL signals.  Would you be able to advise
>> on a simple buffer circuit that would allow me to drive the usual
>> unbalanced 50-ohm coax please?
>>
>> Thanks,
>>
>> Peter Vince  (London, England)
>>




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