[Premium-Rx] Frequency Standards

[Terry O'Laughlin]

I have an HP Z3801 and Trimble Thunderbolt GPS standards running side by 
side in my shop.  After a few weeks, I donated all my other standards to my 
local technical college (where I teach).  Nothing came close to the 
accuracy and ease of the Thunderbolt.  I think of the Z-3801 as my backup now.

I found the Thunderbolt on eBay for $175 and bought two.  I donated the 
other one to the college and it is our shop standard.  They are amazing 
units.  The Thunderbolt is much smaller (about the size of two hard drives) 
and uses 60% less power than the Z3801 (at 24VDC which is easier to 
supply).  It also receives more satellites (12) at lower signal levels and 
appears to be more accurate, although it is beyond the limits of my 
equipment to compare the accuracy with the already excellent Z3801.

Terry O'


At 02:55 PM 7/5/2003 -0400, you wrote:
>GandalfG8 at aol.com wrote:
>
>I used to use an ovened crystal standard with distribution amp, built 
>in-house by Siemens in the UK,  but there was always the niggling doubt as 
>to how well calibrated it actually was.
>
>That's a problem if you operate stand-alone. Hence the need for a receiver.
>>When the Z3801A GPS units became available that seemed like the ideal 
>>answer, and probably still is, but I just couldn't resist the rubidium 
>>unit. I've realised that it's as easy to get hooked on nice test gear as 
>>it is on radios:-)
>Tell me about it !! Just as expensive too.
>>This particular Racal standard is quoted as having an accuracy of plus or 
>>minus 5 parts in 10 to the minus 11 per month, or 5 in 10 to the minus 10 
>>per year, and I doubt that it's even two years old yet.
>That's somewhat better than the specs on crystals, but in my experience 
>crystals are very often 10x better than spec if you let them run for a 
>long time (months or years). My crystals have been running 5 years plus 
>and are about as good as Rbs. BTW, Rbs are really crystals, locked to the 
>Rb cell.
>>Other than having a desire for things being spot on, or as good as 
>>possible anyway, I think it will take quite a while before that degree of 
>>drift is going to matter much for me.
>True. Unless you are doing very special stuff (like physics research), 1 
>in 10 E 10 is just fine.
>>What is the recommended calibration interval for something like this?
>I don't know the 'official' schedule. I just tweak my unit if the freq. 
>goes off more than 1 in 10 E 10. The frequency always increases, so I move 
>it down 2 in 10 E 10. Easy.
>
>Take care,
>John
>>
>>regards
>>Nigel
>
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