User Manual

OSMAC BaseOSMAC Base User Manual
Page 41
12 Alignment
12.1 Adjustments
The following table lists the internal adjustments.
Reference
Designator
Function
Rear Panel Squelch/carrier detect threshold level.
Rear Panel LCD Contrast.
R20 Receive audio level.
R16 RX audio bias.
R32 CTCSS encode level.
R34 Paging data level.
R41 Voice limiter.
R60 Microphone gain.
R52 Telco audio to transmitter level.
R69 Telco line driver level.
12.2 Alignment Procedure
12.2.1 General Setup
1. Apply DC power to the unit. Connect the service monitor to the ANT port.
2. Download the Flash code to the unit if it is not already programmed. Hold down the "-" key while
powering up the unit to enter Flash code programming mode. See the section on "Firmware Updating" for
additional information.
3. Adjust the LCD contrast control on the rear panel of the unit.
12.2.2 Radio Interface
This procedure assumes a properly tuned transceiver is installed in the unit. You will need a DC power source,
service monitor, oscilloscope, and DVM. Full System Deviation =5.0 kHz for wide-band versions, and
FSD=2.5 kHz for narrow-band versions. Depending upon the type bandwidth of the transceiver used, you will
have to make slightly different adjustments.
1. Program the unit’s transmit and receive frequencies. Disable sub-audible signaling.
2. Set the TX bandwidth to “wide band” or "narrow band" depending on the bandwidth of the transceiver unit
installed.
3. Generate an RF carrier on the receive frequency, 1 kHz tone, 60% FSD = 3 kHz (wideband units) / 1.5
kHz. (narrowband units), RF level 10 uV.
4. Adjust R16 for a 1.5 V p-p (530 mV RMS) signal on TP8.
5. Adjust the RF generator to .35 uV. Adjust the squelch (located on the rear panel) so that the carrier detect
LED is on, and so that it goes off when the RF level is below .25 uV.
12.2.3 Telco Interface - Receive Mode
1. Generate an RF carrier on the receive frequency, 1 kHz tone, 60% FSD = 3 kHz / 1.5 kHz. RF level 10 uV.
2. Connect the TELCO line to the RX audio by holding the 1 button down on power up to bring-up the test
mode, then enter the password and press 6 F1 and F2.
3. Adjust R69 (telco line level) for a level of –13 dBm on the line.