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The frequency modulated 146 to 148 MHz signal is amplified by QZ l 0,
2SC741, Q211, 2SC730 and Q212, MRF212 and applied through a two
stage pi-network to the antenna.
A diode D204, 1S188FM rectifies
a small portion of the RF output and applies the resultant DC voltage
to the meter where is provides an indication of relative power output
from the transmitter,
The meter sensitivity is adjusted by VR204
and it is set for indication of 8 on the meter scale at 10 watts on a
50 ohm resistive load.
If the transmitter is keyed without an antenna connected, or if a high
SWR exists in the antenna system, the reflected power is detected
through TZ l 0 and a diode D207, 1S188FM produces DC voltage.
Q215, 2SC372Y conducts with the DC voltage applied through VR209
causing QZ 16, 2SC372Y to decrease its collector current.
Thus,
the emitter voltage of QZ l 7, 2SA49 6( 0) is lowered causing Q
1,
2SD313 to decrease current and the supply voltage to the PA amplifier
Q212 is lowered to prevent damage of the transistor.
The protection
level is set by VR209.
This circuit is also used to switch the output
power down to 1 watt where the HI/LOW switch is set to LOW position.
The amount of power reduction may be adjusted by VR208.
The antenna change -over circuit consists of the switching diodes
D205 and D206, Ml 301.
RECEIVER SECTION
The 146 to 148 MHz input signal from the antenna is amplified by
FET Ql0l, 3SK40Mon RF board, and applied through five hi-Q
slot-coupled resonators to the first mixer, Ql02, 3SK40M.
,-~
~~---
--,
,..,,..,,__
01
02
-
,;c,-;;;;a:--;.;= =
~-=-i
Q
l03
0
104
0
11
3
X
10
1
01
1 ,1
Q
,
05
Q
,
06
a,
07
Figure 8
Top View
14
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