Park Air Systems T6T, User Documentation

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T6T VHF 100 W Transmitter Page 8 Specification
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Mode 3
This section gives the transmitter specification applicable to Mode 3 operation. Mode 3 parameters are
identical to AM-Voice mode parameters with the following exceptions:
RF Power Rise Time
The transmitter produces more than 90% of full power output within the first 2 symbols of the power
stabilization segment, which is the first segment of the training sequence and consists of 4 symbols each
representing 000.
RF Power Decay Time
The output power decays by more than 20 dB within 2.5 symbols of the middle of the final symbol.
Channel Spacing
25 kHz channel spacing only.
Transmitter 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. Information is
differentially encoded with 3 bits per symbol transmitted as changes in phase rather than absolute phase.
The data stream is divided into groups of 3 consecutive data bits, least significant bit first. Zeros are
padded to the end of transmissions if needed for the final channel symbol.
Modulation Rate
The symbol rate is 10,500 symbols/second (±0.005%), resulting in a nominal bit rate of 31,500 bits/s.
RMS Phase Error
The RMS phase error is less than 3°. The error vector magnitude is less than 6%.
Phase Acceleration
The total frequency change during the transmission of the unique word is less than 10 Hz. After this, the
phase acceleration is less than 500 Hz/s.