[time-nuts] means of calibrating/verifying Ru with GPS
not.again at btinternet.com
Mon Dec 24 03:35:19 EST 2007
On Sat, 22 Dec 2007 22:02:49 +1300, you wrote:
>> Hi everybody,
>> I mentioned some time ago that I had an Ru 10MHz source and I would like
>> to calibrate it. I have an hp 5335 counter and a Jupiter GPS with 10kHz
>> output. I was wondering if I could use the Ru 10MHz as and external
>> clock for the 5335 and then measure the frequency of the 10kHz gps
>> locked signal and adjust the Ru to read exactly 10kHz? If I let the
>> 5335 average the frequency input it will display 12 digits - how many of
>> those are reliable I'm not sure but it seems that this may be an easy
>> way for me to check the Ru.
>> Is this a viable method or am I missing something - I haven't done a lot
>> of research into the time keeping world yet.
>> Also, the model Ru I have is the Efratrom frk-h with external frequency
>> control. I have had a quick read of the manual but can't find any
>> information on how this works. I was thinking this might enable me to
>> discipline the Ru to GPS - does anyone know how this works?
>> Thanks for your help
>> Happy holidays
>The biggest problem with your proposed measurement scheme is that the
>10kHz signal is no more stable than the PPS output.
>The 10kHz output is phase jerked every second to realign it with the UTC
>This behaviour is clearly documented in the receiver datasheet.
All the docs I've seen are rather functional in their description, and
short of detail. I was curious how exactly the 10KHz is generated, how
it's "aligned", and the precision/position of each rising edge -
anyone got any info on this?
>Thus to reduce the measurement error due to this instability to better
>than 1E-10 or less the counter gate time will need to be around 1000
>seconds or more.
>Adjustment to better than 1E-10 will be somewhat problematic not to say
>Fortunately the 5335A maximum gate time is 1E7 seconds or about 4
>months, so this may actually be possible.
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