[time-nuts] Confusion over Thunderbolt - noob is going crazy

[Bob kb8tq]

Hi

“Thunderbolt” is the name Trimble uses for their line of GPSDO’s. They have used it for 
almost 30 years. They have had at least a dozen different models within their line of GPSDO’s. 

Back about ten to fifteen years ago, a 911 location system started to be scrapped out. It was being
replaced by newer / better / whatever systems. That location system happened to use a slightly
customized version of one of the Trimble GPSDO’s. Like all the rest, it was called a Thunderbolt. 
They hit the market in large volume and prices dropped. Also some nice people actually did some
work on group buys to help sort things out. All of that got a lot of attention focused on them.

Indeed after some poking at them, some turned out to be a bit better than others. Units with date
codes past about 2005 or so have better OCXO’s in them than units before about 2000. In-between 
those dates, the OCXO’s got progressively better. Firmware wise, things got updated over the years. 
At some point the temperature sensor IC’s went a bit sideways and the temperature readout suffered. 

The China reclamation process is not kind to gear. It often sits out in the rain for quite a while. That
does not do the gear any good. The level of “testing” done by any of the sellers is superficial at best. 
Even “back in the good old days” one might find one in five units with a problem. Indeed, it’s quite possible
that after sitting in a dusty corner of the basement, some previously good units now have issues. 
Stuff happens. 

The unit that gets all the press has two BNC connectors and an F connector  out one end and a 9 pin 
serial port. There is a power connector coming out the top of the unit. It is about an inch thick. The 
enclosure is not painted on most units. 

If the cover is on the unit, there is no way to see what’s on the PC board. A “real” unit comes with the
cover / enclosure. The only easily read label on the PC board is the label that shipped on the OCXO
when it went out to Trimble. The red “Piezo” labels are early OCXO’s. The later OCXO’s have slightly
off white labels on them. 

If you get a unit with a problem, there are no schematics. There also are no firmware images. There is
information on replacing the temperature sensor IC and on replacing the RS-232 driver chip. They are
the “original” unit that worked with LH so support there is very good. 

Performance wise they are good units, but hardly unique. There are a lot of devices out there that 
perform worse. A properly designed Rb based unit would beat them in most respects. 

Bob

> On Nov 14, 2019, at 11:02 PM, Taka Kamiya via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> I hope I don't get yelled at for asking this question.  I honestly looked everywhere and still can't get this.
> I have several GPSDO but I don't have a TRUE Thunderbolt.  I want one.  So I started looking.  There seem to be infinite variations of them.  So far (I have been looking for a week), there are no good summary (or even a summary) of various types and how they are different.
> I know there is a thin type that looks to be 1" or so thick, and thick type that is about double that.I know thick type can have blue label with current Tbolt E, or red label (read somewhere this is an earlier one?)
> I know there is a type that contains inferior oven and better one.  (Marked Trimble)I know there is a type with F connector for antenna, and there is one with BNC.I know there is an early type and late type.  (I don't know how to tell)I know the latest one is T-boltE, which is not necessary similar to earlier ones.I know there is a type that requires single voltage and 3 sources.
> What I don't know is:
> How many different types are there.Any particular one to avoid?  I know there were some experiment done with replacing OCXO of earliest type.Why form factor change?  OCXO does not seem to be any taller....Spending $1500 for new one is out of question, but price seems to vary from $150 to $500 for used ones.  Since most of them come from China, I'd think they are reclaimed equipment.  Is this assumption right?
> Any reliable source?  I am a bit skeptical with the market the way it is.Are they all telecom quality?  
> 
> Thank you very much.
> 
> 
> --------------------------------------- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
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