[time-nuts] Tait reference

David C. Partridge david.partridge at perdrix.co.uk
Mon Jan 11 10:40:45 EST 2016


Is it possible to tell by looking at the back of the unit to determine if an Rb is fitted?

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Stephen Tompsett
Sent: 11 January 2016 14:13
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Tait reference

The T801 units I have seen in the UK contained a rubidium 10MHz reference (FRS form factor) and a synthesizer that could produce several outputs of a nominal 12,8MHz, but which could be individually offset slightly to allow for precise offsetting of the transmitter frequencies by a few Hz for use in a quasi-synch PMR system.

On 11 January 2016 at 11:18, Charles Steinmetz <csteinmetz at yandex.com>
wrote:

> Adrian wrote:
>
> Are these the references with a rubidium oscillator ? They seem to 
> have
>> similar models with OCXOs etc.
>>
>
> Tait is a manufacturer of mobile communications gear in New Zealand.  
> The
> T801 was part of a discontinued "quasi-synchronous communications system"
> -- a form of simulcasting on the same frequency by transmitters at 
> different locations, to fill in dead spots.  Tait's application was 
> utility and public service mobile radios (not radio broadcasting, 
> where this scheme has also been used).  Here is Tait's basic description:
>
> The Tait Quasi-Synchronous Communication System works by broadcasting
>> simultaneously from several transmitters on the same frequency. The 
>> transmitters then operate as a single transmitter giving superior coverage.
>>
>> A Tait T801 Frequency Referenct Module acurately maintains the 
>> frequency of the transmitters at each site.
>>
>> Where required, the T801 allows small frequency offsets to prevent 
>> the occurrence of static nulls in the overlap area.
>>
>> The T801 module may be driven from one of a number of frequency 
>> references, such as:
>> -- Rubidium frequency standard
>> -- Broadcast frequency standard
>> -- Oven Controlled Crystal Oscillators (OCXOs)
>> -- GPS Caesium Clock
>>
>
> This suggests that the T801 does not have an internal frequency 
> reference, but rather requires a precision external reference to 
> function.  (It has a jack labeled "INTERNAL STD OUTPUT," but that may 
> simply be a reference that is derived from the external standard, or a 
> backup crystal oscillator to keep the transmitter more or less on 
> frequency if the external reference signal is lost.)
>
> Best regards,
>
> Charles
>
>
>
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-- 
Stephen Tompsett
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