[time-nuts] HP Z3801A Question

ernieperes at aol.com ernieperes at aol.com
Thu Nov 13 17:37:57 EST 2008

Hello Said,

Thanks for the detailed reply, it makes sense.
But both unit , the HP and the FURY board running under the same 
software simultaneously / GPS Con / and I was mentioning the same small 
"windows" TI to GPS, and the FURY displays much better figures then 
HP.....but probably each units gives out / display / different 
Also the graphic display / BLUE / on the FURY board the max ampl 
between +2,2nsec and -2,0nsec sometimes +0,7nsec ,
the HP unit never goes under +15nsec and -20nsec...... almost 10 times 
Anyhow I am happy because it seems to me that the HP is still OK after 
3 years of sleep.....

Rgsa Ernie.

-----Original Message-----
From: SAIDJACK at aol.com
To: time-nuts at febo.com
Sent: Thu, 13 Nov 2008 10:41 pm
Subject: Re: [time-nuts] HP Z3801A Question

Hello Ernie,

as Bjoern mentioned I think the HP is indicating Time Interval between 
and OCXO 1PPS in nanoseconds, while the Fury is indicating estimated 
accuracy, a unitless number.

The Fury is showing estimated average frequency error over the last 
seconds, similar to AVAR 1000s.

You can run GPScon on Fury too, and should be able to compare against 
graphic you did for the HP unit.

Or you could set the LCD of the Fury to show Time Interval to UTC, or 
this time interval to UTC with the command ptim:tint? that will return 
offset in nanoseconds as well.

An offset of +/-50ns to UTC seems to be normal for the HP unit. On the 
I would expect this to be +/-10ns on a good OCXO.

To the benefit of the Z3801A unit: if the HP unit indicates a larger 
it may also be because it's internal GPS is not as good as the Fury 
receiver. It does not necessarily mean the OCXO is causing the error, 
it could
be that the HP GPS is causing the error, and the HP OCXO is still 
because it filters out its higher GPS errors.


In a message dated 11/13/2008 02:45:57 Pacific Standard Time,
ernieperes at aol.com writes:

And running parallel the FURY board with a TEMEX OCXO and displays
+1,6E-10 is the average very often 10E-11 and sometimes for a relative
short time / 4-5 min / 1,4E-12.

Any idea why the Z3801A not displaying better figure?? Something wrong
with the HP unit????

Thanks Ernie.

time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to 
and follow the instructions there.

More information about the time-nuts mailing list