DANIELS
ELECTRONICS LTD.
TM
3-8
IM10-VR3H040-AB VHF Enhanced Extra Wideband Receiver Instruction Manual
3.2
Enhanced Front End
3.2.1
General
The Enhanced Front End amplifies and down converts the RF signal to the IF frequency of
21.4 MHz. The FE3H035 and FE3H045 Front Ends use high side injection. The Enhanced
Front End consists of the following:
• Five Section L-C coupled Bandpass Filter
• Single Stage Low Noise RF Amplifier
• Image Rejection Filter
• Local Oscillator Low Pass Filter
• Double Balanced Active Mixer
3.2.2
Power and Interconnection
The FE3H Enhanced Front End operates from +9.5 Vdc applied via a short red wire connected
to supply point J6-2 on the receiver main IF/audio board. Ground return is supplied via direct
mounting to the receiver chassis and coaxial cable interconnections. The FE3H Front End draws
approximately 160 mA from the IF/audio board’s +9.5 Vdc supply.
The RF input signal connected to the receiver front panel type N connector is fed to the front end
SMB input connector (J1) by a short coaxial cable. The FE3H Front End’s local oscillator input
and IF output are respectively routed by coaxial cable from the local oscillator module and to
SMB connector J7 on the main IF/audio board.
3.2.3
Preselector Filter
The received RF signal is filtered by a five section L-C coupled band pass filter. This filter
provides front end selectivity and attenuates any potential antenna conducted spurious signals.
The filter has an operational bandwidth of 5 MHz and a typical insertion loss of 2 dB. The filter
is tunable (L1 through L5) in the following ranges :
• FE3H035
29.0 MHz - 38.5 MHz
• FE3H045
37.5 MHz - 50.0 MHz
Every Enhanced Front End has an identification label indicating one of two operating frequency
bands.