[time-nuts] Measuring Rubidium frequencies

Bill Hawkins bill at iaxs.net
Fri Jun 6 19:44:26 UTC 2008


It might be even easier than that.

As a long-time user of the 1992, I know I'll get weird results
if I fail to turn on the 50 ohm terminator for the input(s).

Your 1992 will also do phase A-B measurements. This is a great
way to compare standards if you don't have the expensive stuff.
Don't know about the terminator for the external standard since
I don't use it, using phase instead.

Bill Hawkins


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Adrian
Sent: Friday, June 06, 2008 12:10 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Measuring Rubidium frequencies

Jim,

it might be much easier than you're thinking...

Are you sure the GPDSO's are locked?
Are you sure the rubidium oscillators are locked?
What is the reading of your GPDSO's when you measure them with the
internal counter time base?

I would say that neither 0.00001722 nor 0.00000000 can be correct for a
10.000,000 MHz signal.
Something with your figures appears to be dead wrong, IMO.

Adrian


Jim Robbins schrieb:
> Hi all,
>
> I have a problem which I am unable to understand and need some help.
I have two M100 Rubidiums, a Racal 1992 counter, a factory standard
T'Bolt and a Symmetricom Starloc II.  When I set up either GPSDO as the
External Timebase for the 1992 and measure either Rubidium, I get the
same reading of 9.99998278.  When I use the 1992's Internal Timebase, I
get 9.99999995.  All equipment has warmed up.  The antenna is a
Symmetricom HP 58532A on the roof.     On a few occasions I have seen
the frequency drift up to 0.00001722.  I would have expected that both
Rubies would have read 0.00000000.  Any ideas would be much appreciated.
>
> many thanks,
> Jim Robbins






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