Ramsey Electronics FX-440 Manual page 28

Stage TX: Transmitter Buffer. Driver and Final
The transmitter section, 010, 09 and 08, is conventional UHF RF
circuitry that has proven quite reliable in Ramsey FM transceivers. Just a
few circuit notes are in order.
Transistor 010, the transmit buffer, amplifies the VCO output from C56 to
about 10 milliwatts, quite sufficient for checking modulation and PLL
alignment in transmit mode as soon as this stage is built. Operating bias
is supplied by the PLL lock detect voltage from USB through R110. If the
PLL. unlocks, 01 O does not operate, preventing the radiation of
out-of-band signals.
The MRF-559 Driver, 09, amplifies the output of 010 to drive 08 to its
full rated output. 08, the popular MRF630 or its equivalent, has package
characteristics which the user should grasp clearly. Through
beryllium-oxide insulating technology, the emitter is common to the case.
There is significantly better gain because there is no emitter lead length
to speak of. The small device can handle large power dissipation IF the
case is properly soldered to the ground plane of the PC board as detailed
in the assembly instructions. So as not to compromise the gain efficiency
of 09, C75A and Bare SMT "chip capacitors" installed on the solder side
of the board.
The PIN T-R diodes 07, D6 and D2 are discussed in section DR. In brief,
D7 passes RF to J3 during transmit while D2 and D6 protect the receiver
RF input. The antenna input is designed for a 50 ohm resonant antenna
C84 and C74 are adjustable to peak RF output (2 to 4 watts).
Ref. 26
FX-440