DANIELS
ELECTRONICS LTD.
TM
VHF Enhanced Extra Wideband Receiver Instruction Manual IM10-VR3H040-AB
2-1
2
SYSTEM OVERVIEW
2.1
Receiver Operation
A VR-3H040 Receiver family is constructed using three primary modules; the FE3H Front-End
module, the MT-3 Receiver FM IF/Audio Main Board and the OSR-3H061 local oscillator
synthesizer (refer to section 3.3, VR-3H040 Family Enhanced Receiver Block Diagram).
Two Front-End modules, FE3H035 and FE3H045 provide frequency coverage from 29 - 38
MHz and 38 - 50 MHz respectively. Tuning within each frequency band is provided through
five ferrite core slug adjustment points. The FE3H Front-End (FE3H035, FE3H045) combines a
low noise BJT amplifier with a cascaded, multiple pole, high selectivity coupled resonator filter
structure. A high intercept point active mixer is also located within this module. The module
has inputs for the RF signal (Front Panel N connector), local oscillator input signal, and an
output for the 21.4 MHz IF signal which connects directly to the FM IF / Audio Main Board.
Interconnections are made using quick connect SMB style connectors.
The MT-3 Receiver FM IF/Audio Main Board accepts the IF signal of 21.4 mHz. The signal
passes through the following stages: selective crystal filtering, amplification, second IF
frequency conversion to 455 kHz, and final audio FM demodulation / amplification. The board
provides a high degree of receiver flexibility by providing a number of different audio paths,
audio levels, and control interconnect options.
The OSR-3H061 Synthesizer Module produces a low noise, high stability RF local oscillator
signal covering the frequency band of 50.4 - 71.4 MHz which translates to a receive frequency
range of 29 - 50 MHz. The internal TXCO is used for frequency stability, but an external
reference signal may also by used.