Circuit Description; Receiver; Circuit Diagrams - Motorola MR 11 Service Manual

Transmitter power
Current consumption
Standby
Receive
Transmit
6 W
10 W
12 W
25 W
3

Circuit Description

The circuit description and its component references refers directly to individual components in
part which can only be found in the design circuit diagrams.

3.1 Receiver

The complete receiver module consists of the VHF/UHF pre-stage (RX), a ring mixer, the IF unit
(IF) and a power supply (PS).
Pre-stage (RX)
The pre-stage is responsible for far-off selectivity, attenuation of the image frequency and the total
sensitivity. The circuit consists of two band pass filters and one amplifier in emitter circuit. The pass
range is divided into four reception ranges by two varicaps in the first band filter. The analog signal
VRXTUNE controls the respective reception range.
The second band pass filter could be omitted from the MR radio on account of the good selection
of the harmonic filter.
Double Balanced Mixer
In the double balanced mixer, the reception signal is mixed down to the 1st IF level by the applied
oscillator signal.
Motorola GmbH • Geschäftsbereich Funksysteme
I
MR 1116
0.1 W fixed
1 - 6 W
6 - 12 W
12 - 25 W
Channel-dependently programmable Channel-dependently programmable
< 0.3 A
< 0.5 A
< 2.3 A
—-
< 3.5 A
< 6.8 A
.. - 1 << >>
MR 1142
MR 1145
0.1 W fixed
1 - 6 W
1 - 10 W
10 - 25 W
< 0.3 A
< 0.5 A
< 3 A
< 3.5 A
—-
< 7 A
MR 11
2 - 3