TN213 VR-3A130-SYF VHF AM Enhanced Receiver
MT-3 Radio Systems
TECHNICAL NOTES
TN213 Rev 8-0-0 May 14
Page 2 of 2
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Squelch Adjustments:
Receiver squelch action is factory set to establish a
squelch hysteresis window of 4 dB, such that the squelch
closes at the 8 dB SINAD point and opens 4 dB above.
Eg. if the receiver 8 dB SINAD point is -108 dBm the
receiver should be set to unsquelch at -104 dBm and
squelch at -108 dBm. Rotate the squelch hysteresis
adjust potentiometer (RV8) and the squelch threshold
potentiometer (RV7) fully counter clockwise. Inject a 1 KHz
tone at 30% modulation at the 8 dB SINAD level. Note
the RF level and then increase it by 4 dB. Slowly adjust
the squelch threshold potentiometer (RV7) clockwise
until the receiver squelches. Change the RF level back
to the 8 dB SINAD level noted earlier. Advance the
squelch hysteresis adjust potentiometer (RV8) clockwise
while momentarily pressing the squelch disable switch
repeatedly, until the squelch gate just stays open. Then
adjust the squelch hysteresis adjust potentiometer (RV8)
counter clockwise without pressing the squelch disable
button until the squelch gate just closes.
Front End Alignment:
No front end alignment is required. The enhanced synthesized receiver uses an elliptical band pass
fi
lter that is
tuned at the factory for the entire frequency band of 118 - 137 MHz.
Synthesizer Alignment:
No synthesizer alignment is required. The synthesizer is factory aligned for use over the entire frequency range.
Frequency Select Handle Operation:
The frequency select handle is used to designate the operating frequency for channel 16 of the AM RF module. To
operate the frequency select handle, set the AM module on channel 16 (using the motherboard jumpers, external
control or rotary switch option) and ensure jumper JU73 on older motherboards (pre-2009) is installed.
1) The display is normally in a low power sleep mode. To display the current frequency, press either the
(decrease
frequency) or the
(increase frequency) buttons. This will display the current channel number (for 2 seconds), then
the current frequency (for 3 seconds). The display will then go back to sleep.
2) Press the * (center) button to display the current lock status (“Locked” or “Unlocked”). To lock the buttons, press
the
button, and to unlock the buttons, press the
button.
3) To change the current operating frequency, ensure the lock status is “unlocked”, press either
or
to wake up
the display, then use the
or
buttons to change the frequency. The
or
buttons have two modes of operation.
Single press the buttons for single channel steps (8.333 KHz). Hold the button in for 6 seconds and the frequency
will change by 66.66 KHz per step, and after 9 seconds of the button being pressed the frequency will change by
166.66 KHz per step. The operating frequency is set to the displayed value once the
or
buttons are released.
Remove the four front panel screws (A) and two side panel screws (B)
to slide the receiver outer cover off and expose the Receiver Main Board
and Synthesizer. Two holes on the side of the case have no screws.
B
B
A
A
A
A
Note: For complete alignment procedures, refer to the instruction manual. These notes are for reference only.
This product has been discontinued and is no longer manufactured by Codan Radio Communications
