Motorola MR 11** TD-R Manuale di servizio - Pagina 5

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IF Module

The IF module amplifies the 45 MHz signal from the mixer and provides the necessary channel

selection by the available crystal and ceramic filters. It supplies a demodulated AF signal to the

following AF-IC and provides the computer with an RSSI (received signal strength indicator) signal.

Power Supply (PS)

The power supply generates the necessary receiver voltage VRX. VRX is derived from the switched

battery voltage BATSWD and stabilised at 8 V. VRX is switched on and off by the control line

VTXCTRL.

3.2 Transmitter

Four adjustment values for four power stages are stored in the radio for the transmitter output

stages in production. One of these values can be assigned to the "High Power" stage switchable by

the user, another to the "Low Power" stage with the help of WinIPP in the after-sales service. This

can be done uniformly for all channels or separately for each channel. To ensure as constant as

possible an output power over the whole frequency range, four times four setting values for 146

MHz, 155 MHz, 165 MHz and 174 MHz are determined in automatic adjustment.

The switching times for reception-transmission, transmission-reception mode are less than 30

milliseconds. The power supplies for the transmitter are switched on and the T/R switch switched

to transmission mode via the control line VTXCTRL.

Transmitter Ouput Amplifier

The transmitter is available in three power ranges (1-6 W / 6-12 W / 12-25 W). The stored adjustment

values for the transmitter power in the MR radios are:

1-6 W:

1 W

6-12 W:

6 W

12-25 W:

12 W

The transmitter power of the MR 11 is keyed up with the aid of a D/A converter in the form of a

staircase function in two milliseconds. The setting values are passed to the transmitter via the

control line VPWRREF after a linear interpolation.

The antenna filter connects either the receiver pre-stage or the transmitter output to the antenna

socket. Its transmission function has band pass character. Switching is effected by PIN diodes.

The MR 11 harmonic filter is a low pass.

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2 W

6 W

12 W

25 W

.. - 1

6 W

12 W

25 W

MR 11

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