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T801-4 Installation and Operation Manual
Description
17
© Tait Electronics Limited September 2007
FREQUENCY
OUTPUT 1 & 2
The frequency reference outputs are available on these BNC connectors.
The T801-4 with one Satsync 7 module has two output frequency channels,
and the T801-4 with two Satsync 7 modules has four output frequency
channels. Each channel has two ports.
The frequency reference outputs have the following characteristics:
These outputs can be used to supply TB8100 and TB9100 reference
frequency inputs (input impedance >1k
Ω
). In this situation the
recommended maximum number of daisy-chained loads for each frequency
output connector is 8. Each daisy chain must end with a 50
Ω
termination.
The accuracy of the frequency reference outputs is as follows.
■
With a valid GPS fix and the master oscillator locked, the accuracy tends
to ±1 part in 3
×
10
9
(depending on the installation).
■
Without a valid GPS fix, but with the master oscillator control voltage
fixed, the accuracy is subject to ±1 part in 5
×
10
7
(±0.02ppm), over the
quoted temperature range.
■
Without a valid GPS fix, and with the master oscillator following an
ageing trend, the accuracy will be determined by the ageing correction
process (refer to
“Ageing Correction Process” on page 30
) or, if there is
insufficient long-term data, by the characteristics of the crystal. The
ageing characteristics of the crystal, as specified by the manufacturer, are:
- first year (after initial 30-day running time)
±0.1ppm
- later years
±0.1ppm/year.
Accuracy is determined by comparing the master oscillator frequency with
the GPS-derived 1PPS signal. The figures given here are typical of systems
examined in a stable environment, and are subject to variation of the GPS
1PPS signal, which will average out over time.
GPS ANT
This connection on the rear panel is a 50
Ω
female SMA connector. It not
only provides the RF input connection for the optional internal GPS
receiver, but also provides the 3.3VDC power to the active antenna. Tait
supplies and recommends the Trimble Bullet III active GPS antenna.
b c
■
impedance
50
Ω
■
signal type
sine wave, levels programmable from
185mVpp to 2Vpp minimum
(approx. –10dBm to +10dBm)
■
frequency range
50Hz to 25MHz
■
frequency resolution
0.025Hz
■
maximum coaxial cable length
30m
d