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@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@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 > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- Stephen Tompsett _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.