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Circuit Description
Low Current Base Tech 3.5
DESCRIPTION OF CIRCUITS TO STABILIZE TX AND RX FREQUENCY
The transmitter and receiver each use a TCVXO (Temperature Compensated Voltage-Controlled Crystal
Oscillator) to generate the 12.00 MHz reference frequency used within their respective PLL and VCO
circuits. The accuracy of the TCVXO is better than +/- 0.00015% over the range of –30 degree C to +60
degree C.
DESCRIPTION OF CIRCUIT TO SUPPRESS SPURIOUS EMMISSIONS AND MODULATION LIMITING
A multiple pole Low Pass Filter is used after the final power amplifier stage. It is designed to sharply
attenuate spurious and harmonics frequencies above the highest frequency in the sub-band of the radio.
Modulation limiting is performed by TX audio processor, CMX7041L4, located on the Analog Logic Unit.
Internal limiting/compression amplifier provides excellent limiting with minimum distortion.
In addition to modulation limiting, this device contains all circuitry to perform pre-emphasis, band pass
shaping and CTCSS/ DCS encoder.
ANALOG LOGIC UNIT
1) Microcomputer (CPU) Section
CPU IC1, H8S2239 is the 16-bit processor contained 320kb flash memory 6k RAM inside. The CPU
controls all functions of Base Tech III. A flash memory permits on-board-up-grade when new firmware
is released.
2) EEROM Section
IC6 is the 64k bit EEROM. This memory contains all the channel data
3) Audio Processor Section
IC2 is for TX and IC3 is for RX audio processors. CTCSS and DCS are processed within these audio
processors. In previous releases the CTCSS and DCS were processed within separate processors.
This also improves current consumption and simplifies the sub-signaling routines.
4) Low
Current
Improvements
A DC-DC converter (IC 43) has been added to replace the analog 12 volt to 5 volt regulator (IC5).
The DC to Dc converter runs at 170kHz and directly regulates 5.5 volts with no losses to heat
dissipation. This significantly reduces overall current consumption.
DIGITAL LOGIC UNIT (DSP)
IC1 acts as the DSP control for both incoming digital signal converting it to analog and analog
signal to C4FM digital signal. External flash memory within IC2, has 4Mb capacity, contains all
data. Program data is stored in 256 k-bytes of memory integrated within IC1.
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© 2012 Midland Radio Corporation
Содержание 91-1060-91-1110
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Страница 25: ...Block Diagram UHF 50 Watt Low Current Base Tech 3 5 21 2012 Midland Radio Corporation ...
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Страница 27: ...Front Panel Unit Schematic Low Current Base Tech 3 5 23 2012 Midland Radio Corporation ...
Страница 28: ...Analog Logic Unit Schematic Low Current Base Tech 3 5 2012 Midland Radio Corporation 24 ...
Страница 29: ...VHF RX Main Unit Schematic Low Current Base Tech 3 5 25 2012 Midland Radio Corporation ...
Страница 30: ...VHF RX VCO Unit Schematic Low Current Base Tech 3 5 2012 Midland Radio Corporation 26 ...
Страница 31: ...VHF TX Main Unit Schematic Low Current Base Tech 3 5 27 2012 Midland Radio Corporation ...
Страница 32: ...UHF RX Main Unit Schematic Low Current Base Tech 3 5 2012 Midland Radio Corporation 28 ...
Страница 33: ...UHF RX VCO Unit Schematic Low Current Base Tech 3 5 29 2012 Midland Radio Corporation ...
Страница 34: ...UHF TX Main Unit Schematic Low Current Base Tech 3 5 2012 Midland Radio Corporation 30 ...
Страница 35: ...Front Panel Unit Layouts Low Current Base Tech 3 5 31 2012 Midland Radio Corporation ...
Страница 36: ...Analog Logic Unit Layouts Low Current Base Tech 3 5 2012 Midland Radio Corporation 32 ...
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Страница 43: ...Palm Microphone Schematic Low Current Base Tech 3 5 39 2012 Midland Radio Corporation ...
Страница 62: ...5900 PARRETTA DRIVE KANSAS CITY MISSOURI 64120 PHONE 816 241 8500 FAX 816 241 5713 www midlandradio com ...