1-2
1.2 DESCRIPTION (continued)
To improve the rejection of interfering signals, dual conversion receiver technology has been incorporated
on the Receiver (Module A1) board used in Technisonic VHF/AM base stations. The second IF is 455kHz
using a ceramic filter, which is immune to high energy ringing. The dual conversion module also has a
second local oscillator, second mixer and ceramic filter. The first local oscillator is the original VCO.
The dual conversion receiver board, P/N 003494-3 was implemented into TSR series base stations starting in
January 2001. An option label on the chassis will indicate OPTION 94 if the dual conversion board is installed. It is
possible to retro-fit the dual conversion receiver board into older TSR series base station employing the single
conversion board. Please contact Technisonic for availability of an exchange board. Note: If a new A1 Module
has been retrofitted the squelch circuit must be aligned for the receiver squelch to operate correctly.
The dual conversion receiver’s squelch knob must be rotated significantly more clockwise (4 o’clock
position) to obtain the same squelch setting (3uV) as a single conversion receiver’s squelch knob set to the
12 o’clock (straight up) position.
If the dual conversion receiver’s squelch knob is set to the 12 o’clock position, signals with a level greater
than 0.5uV will open the squelch. At most airports this will not be an adequate level of squelch. Please be
aware of this squelch knob adjustment variance when setting and/or comparing squelch levels of dual
conversion vs. single conversion base stations.
1.2.1 Receiver Module
The Single Channel Receiver is based on Transceiver Model 90-6R. The transceiver module is modified for receive
only, on one pre-programmable synthesized frequency, with 25kHz channel spacing in the frequency range
117.975 MHz to 138.000 MHz. The single channel memory set board, module A5A1 is mounted external to the
receiver internal module to facilitate ease of frequency programming. Refer to above paragraph for details on new
dual conversion receiver A1module.
1.2.2 Power Supply Modules - Model SPG-007
The Power Supply Module, Model SPG-007 provides the DC supply voltage to the receiver and houses a battery
charger which can provide charging and trickle charging to an external rechargeable 12 Vdc battery, if utilized.
1.2.3 Mother Board
The Mother Board provides all interconnection between the two external remote control connectors, Power Supply,
Remote Audio Board, and Receiver module. The Remote Audio Board, Optional Crystal Filter and all internal fuses
are mounted on the Mother Board.
1.2.4 Remote Audio Board
1. Line Interface Board P/N 923060-1
NOTE This board is supplied modified for the 92-SC, Receiver without transmitter keying functions
Provides remote receiver audio monitoring over 2 wire 600 ohm audio lines.
