[time-nuts] Need help with TrueTime GPS-XL 600-101

[Skip Withrow]

Greetings time-nuts, 

I have a TrueTime XL-AK (model 600-101-1) GPSDO that requires an 
antenna-mounted down-converter (I'm pretty sure).  Of course, it is still on 
the building from the previous owner of this unit and cannot be made 
available.
The manual does not seem to be of any help either - no block diagram or 
description of the conversion scheme. 

So, any help with understanding this unit would be greatly appreciated.  Or, 
if you have a source for one of these down converters I would definitely 
consider purchase.  The receiver module in this unit is a Trimble and the 
board seems to be marked 22880 at several places. 

Thanks in advance for your time. 

Skip Withrow