Technical Manual

120 20170-201 Paragon
PD
Technical Manual
36
6.2.3 Exciter Module (T881)
Note 1: Refer to Figure 22 on page 40 for locating tuning controls.
Note 2: When the synthesizer is unlocked, the front panel green LED called "Supply" will be
flashing showing that it needs to be re-tuned.
6.2.3.1 Initial Setup
1. Shut down power to the base station
2. Prepare the multimeter to read DC Volts.
3. Remove the exciter (T881) module from the base station rack frame
4. Remove the exciter top cover (nearest the handle).
5. Connect the Paragon
PD
Extender Rail kit between the exciter module and the empty
chassis exciter slot.
6. Connect a 3 feet long double shielded cable (N-M to BNC-M) between the IFR T/R out-
put and the exciter antenna connector.
7. Apply power to the base station
6.2.3.2 Synthesizer Alignment
Single channel: Connect the multimeter to the long lead of L1 in the VCO (this measures
the synthesizer loop voltage). Tune VCO trimmer C6 for a synthesizer loop voltage of
7VDC.
Multiple channels: Adjust the VCO loop to 7V using the middle frequency channel.
All channels should lie within the upper and lower limits of 10V and 3V respectively.
Note: Normally, the fast TX key option is installed and the synthesizer is always ener-
gized.
Where that option was not fitted, key the transmitter by pressing the front panel
Carrier button to make the above adjustment possible.
6.2.3.3 TX Frequency Error Adjustment
1. Apply the following settings to the IFR:
- Receiver mode
- IFR RX frequency to match the main radio TX frequency
- IF Filter (BW) set to 30KHz
- Zoom the RF Error window: select 10Khz range
2. Key the transmitter by pressing the front panel TX-key button and measure the carrier
output frequency. It should be within ±300 Hz. If it is not, adjust the TCXO to trim to
meet the requirement, preferably within 100Hz.