[time-nuts] Thunderbolt GPS Receivers

[Didier Juges]

Yes, the disparity in holdover specifications is striking, even more so 
considering the HP 53540A was obviously designed as a form, fit, 
function replacement (except for the software interface) for the 
Thunderbolt, based on the mechanical dimensions.

Also consider that the Thunderbolt spec was written when SA was in 
effect. We should expect better performance today with SA turned off. 
Trimble never revised the spec. I asked the question (along with a bunch 
of other questions) from the sales guy a month ago but he did not answer 
that one. I guess they probably have not done comprehensive testing 
since SA was turned off.

Didier KO4BB

David I. Emery wrote:
> On Sat, Jan 27, 2007 at 09:57:30PM -0600, Didier Juges wrote:
>   
>> There is also the HP 58540A that looks a lot like the Thunderbolt, but 
>> the specs are not nearly as good. I have not seen any of those on eBay 
>> in a while either.
>> http://www.realhamradio.com/58540A.htm
>>     
>
> 	I'm curious as to whether anyone has actually MEASURED 58540A
> performance and compared it with a Thunderbolt.   Clearly the standard
> 58540A has MUCH worse specified holdover performance, but unless that is
> important to you the actual 1 PPS jitter statistics (ADEV) and accuracy
> relative to UTC and the related 10 mhz stability in various taus would
> be what would count for most of us as actual holdover operation happens
> less often, at least for significant intervals.  And then of course
> phase noise, close and far... counts for many applications too.
>
> 	The Thunderbolt has lots of tweaks and the 58540A few, but for
> many uses this is not a big issue.   Just curious as to how good or bad
> the relative performance is WHEN LOCKED.
>
>
>