[time-nuts] Tait reference

Clint Jay cjaysharp at gmail.com
Mon Jan 11 18:52:36 UTC 2016

Thank you Nigel, I've also taken a gamble on one of these units and am
keeping my  fingers crossed that it has a Rb standard in it.

The service manual is most interesting, it looks like I could use one of
the two 'loops' to lock a different OCXO,  with a little tinkering it could
be a very useful unit as there's plenty of space inside for additions and
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
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
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
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
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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