User's Manual
Table Of Contents
- 1. General Description
- 2. Installation and Operation
- 3. Options
- 3.1 T01 Programmable Channel Spacing
- 3.2 T02 Programmable CTCSS encoder/decoder
- 3.3 T03 Programmable DCS/CTCSS encoder/decoder
- 3.4 T05 Balanced and Isolated VF plus E&M
- 3.5 T06 Simplex Changeover Relay
- 3.6 T08 VF Delay
- 3.7 T09 300Hz Upgrade HPF Filter
- 3.8 T10 Power Save Mode
- 3.9 T11 Combined Options
- 3.10 T12 External Reference Oscillator Input
- 3.11 T13 Local Speaker, Mic Socket and Front Panel Mute
- 3.12 T14 Local Channel Change
- 3.13 T16 1PPM Frequency Stability
- 3.14 U69 Extended Temperature Range Verification
- 3.15 T19/26 Line Interface Board.
- 3.16 T29 Balanced and Isolated VF plus E&M
- 3.17 T31 Network Adapter
- 3.18 T34 Ethernet option
- 3.19 T36 Option - TX Ref Oscillator input and Modulator
- 6. MX800 Base Station Fault Finding Procedure
- 7. Appendices
- 7.1 MX800 Interface Connections
- 7.2 CN2 DB9 Female Monitor Connector
- 7.3 CN3 DB25 Female Digital I/O Connector
- 7.4 MX800 Specifications
- 7.5 Channel Select DIP Switch Settings
- 7.6 MX800 Model Number Configuration Guide
- 7.7 MX800 System Applications
- 7.7.1 Conventional base station/repeater
- 7.7.2 Link transceiver
- 7.7.3 Data transceiver
- 7.7.4 Paging transmitter
- 7.7.5 Trunking Base Station
- 7.7.6 Systems base
- 7.7.7 Repeater with Morse ID
- 7.7.8 Simplex base station
- 7.7.9 Duplicated base station
- 7.7.10 Power Save base station
- 7.7.11 Tone key base station
- 7.7.12 Voting base station
- 7.7.13 Simulcast base station
- 8. Superseded Technical Information
- 9. Drawings
Technical Manual
8. Superseded Technical
Information
8.1 Power Amplifier Module
8.1.1 Technical Description
RF from the Exciter on CN1 is first attenuated by a 50-ohm pad, which is
used to provide good 50-ohm source impedance for the high power hybrid
amplifier IC1. The RF is amplified to between 5 and 13 watts at the hybrid
50-ohm output. The signal from the hybrid is then matched by a broadband
network to drive the low input impedance associated with the final transmit
power amplifier transistor TR1. The transistor's low collector impedance is
then also matched back to 50 ohms by a broadband matching network.
Trimmer capacitors enable adjustment of the power amplifier over a wide
bandwidth so as to maintain good conversion efficiency. Prior to transmission
a low loss 13 element elliptical low pass filter, filters out the unwanted
harmonics to less than -90dBc.
A dual directional coupler consists of coupled microstrip transmission lines
S5, S6 and S7 fabricated on the PCB artwork. The sampled RF energy is
rectified to provide a proportional DC voltage output on CN4-8 (FWD) and
CN4-5 (REFL).
TR2 serves to switch the DC supply to the Hybrid under control of the PTT
line from the Micro Controller on CN4-2. A thermistor TS1, physically
located on the PA heatsink to monitor the heatsink temperature, is connected
to the Micro Controller via CN4-4/6
8.1.2 PA Module Test Procedure
Test Equipment:
Tested MX800 with PA removed
PC with MXTOOLS software
RF Power Meter
RF Signal Generator
Multimeter
+13.8VDC 15A power supply
Preliminaries:
Program upper, middle and lower frequencies of band into 3 channels in
MXTOOLS channel screen. Although the PA will function over a wider
bandwidth, the nominal switching bandwidth of the PA is 10MHz. The
recommended procedure is to centre this 10MHz around the centre of the user
© SPECTRA ENGINEERING 2008 Revision 4.3.1B
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