Multitone RPR 563GS, Техническое руководство

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RPR 563GS/KGS
TM1187A Issue C Page 3 - 7
24. The sub-audio tone derived from IC303 and IC304 (see paragraph 21) is applied to
IC306 via potential divider R435/R444. When DTMF tones are generated by the
Decoder Board, they are applied to IC306a via R419, R420 and R445. The tones are
also applied to IC306b for amplification, rectified by D303 and C451, and applied to
TR341, which mutes the speech circuits from the microphone. This allows DTMF tones
to be transmitted without speech superimposed.
25. IC306 acts as an amplifier and combiner for the speech, sub-audio tone and DTMF
signals to be transmitted. Modulation is taken from RV303 wiper and applied to the
transmitter modulator.
26. The transmitter oscillator is formed by TR301 using a series resonant crystal XL301.
Frequency adjustment is provided by C349. Audio for transmission is applied to varicap
diode D301 which modulates the crystal oscillator frequency. XL301 frequency is
determined by the following formula:
fx = carrier frequency (MHz)
18
where fx is the crystal frequency in MHz.
27. The second harmonic is selected at TR301 collector via C350 and is tripled by multiplier
TR302. The output of this stage has a low `Q' un-tuned output and is coupled to
another tripler TR303 which boosts the level to 0dBm. This signal is applied to SAW
filter FL301 to remove unwanted components before further amplification by TR305 and
TR307. Bias for TR305 is provided by TXDEL and TR304. Interstage matching is
carried out by balun type matching transformers.
28. Power output from the PA is approximately 50mW. Harmonics are removed by low-
pass filter L320, C347, and C348. Inductor L322 maintains adequate matching for the
telescopic antenna even when stowed.
29. At the end of each transmission the Decoder takes the /TxKEY line high.