[time-nuts] Tait reference

GandalfG8 at aol.com GandalfG8 at aol.com
Mon Jan 11 15:41:22 UTC 2016

Are these the references with a rubidium oscillator ? They seem to  have
similar models with OCXOs etc.
Hi Adrian,
The T801 first seems to have hit the UK surplus market around  2005/2006, I 
was told a batch of a couple of hundred, and units from that  release were 
still trickling through until around 2011 at least.
These were released by West Yorkshire Police when updating their UHF  
mobile network and did contain rubidium standards.
The T801 contains dual nominal 12.8MHz  synthesisers with very fine 
switched preset adjustment for base  station synchronisation. These are locked to 
an  external reference and can accept selected integer frequencies  from 1 to 
10Mhz and also 12.8MHz.
If the internal 10MHz rubidium module is fitted and used as the  reference 
then a short BNC link is required to couple the internal  reference output 
to the external reference input.
These were originally sold on Ebay with particular reference to the  
rubidium module, for most purchasers the 12.8MHz synthesiser board would  probably 
have been of little interest, so I'm surprised to see no reference to  the 
rubidium module with the several recent auctions. This may be due to  lack 
of familiarity on the part of the seller but I certainly wouldn't want to  
take anything for granted without asking.
I'm not sure either if the recent Ebay offerings are tail end leftovers  
from that first batch or represent a more recent release, but I have seen a  
number of failures with the rubidium modules in those bought between 2005  
and 2011.
One at least was physically faulty with others refusing to lock,  either at 
time of purchase or subsequently, I have some of the latter still  on the 
ever growing "to do" pile. 
According to the manual the rubidium module, where fitted,  was originally 
a Quartzlock TF4010A, but all units I've seen have been  fitted with FEI 
FE5660A modules. This required a degree of modification to  the chassis and to 
the heatsink and the quality of that work is often poor, so  quite likely a 
field "upgrade". 
The unit also contains a DC-DC convertor to derive the 24 Volt  supply for 
the rubidium module from the 13.8 Volt input.
The lock on the front panel is just an ON/OFF keyswitch, if the key is  
missing all those I've seen have been left in the ON position but it's easily  
bypassed anyway.
I've tried uploading my scan of the manual to Didier's site but gave  up 
after repeated page reset errors, it is now available  here......

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