User's Guide

Page 14
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Transceiver Rx RF Characteristics
Sensitivity
The transceiver has a sensitivity better than -102dBm for 1x10
-3
Bit
Error Rate (BER) with Reed Solomon Decoding off.
In order to improve co-location performance where maximum
sensitivity cannot be realized due to large unwanted signals, the
transceiver’s sensitivity can be reduced by 6 dB. This is achieved by
switching on the 6 dB RF pre-attenuator from the front panel menu
system.
Channel Spacing
Mode 3 channel spacing is 25 kHz.
IF Selectivity
At ±11 kHz from the centre frequency, the signal is attenuated by less
than 6 dB.
At ±25 kHz from the centre frequency the signal is rejected by more
than 80 dB.
Unwanted Signal Suppression
With the required signal at -92 dBm, a BER of better than 1x10
-3
with
Reed Solomon Decoding switched off is achieved under the following
conditions:
❑ An interfering signal at -32 dBm on an adjacent channel
❑ One or more out-of-band interfering signals having a total level of
-33 dBm
❑ One or more VHF FM broadcast signals having a total level of
-5 dBm
❑ Co-channel rejection better than 20 dB.
Synchronisation
For received signals greater than -103 dBm, the probability of
synchronisation is greater than 0.999. The probability of false
synchronisation is 3x10
-3
.
Transceiver Rx Modulation Characteristics
Mode 3 uses Time Division Multiple Access (TDMA) differentially
encoded 8-phase shift keying (D8PSK) using a raised cosine filter with
α = 0.6 (nominal value), emission designator 14K0G7WET.
Wanted Signal Dynamic Range (RF AGC)
A BER better than 1x10
-3
with Reed Solomon decoding off is achieved
for received signals of -102 dBm to +10 dBm. The AGC attack time is
less than 0.5 ms and the decay time is less than 1 ms for a 40 dB step
input.
Frequency Offsets
The transceiver operates with frequency offsets up to 826 Hz.