120 20110-003 PRELIMINARY
Gemini/PD Technical Manual
4
3. Adjustments and
Maintenance
1.1 Overview
This chapter outlines the basic adjustment pro-
cedures required upon initial installation and
thereafter at prescribed maintenance intervals.
Units are delivered from the factory properly
aligned and tested on the frequencies specified
at time of order. Adjustment beyond that de-
scribed in this chapter is not required unless ra-
dio modules have been tampered with or re-
paired. In such cases we recommend complete
factory re-alignment as special test jigs are re-
quired.
3.1 Intended
Audience
This chapter is intended for use by installation
and maintenance personnel.
3.2 Equipment
Required
The adjustments described below require the
following equipment:
•
13.6 VDC (nominal), 20A regulated power
supply.
•
Radio service monitor (IFR or equivalent).
•
Cable with mini-UHF male connector to
connect Gemini/PD to the service monitor.
•
Gemini Radio Service Software,
•
A 486 PC (or better) to run the RSS.
•
Normal radio shop tools.
3.3 Maintenance
Intervals
The adjustments described below should be
done at annual intervals or whenever a deterio-
ration in performance indicates that adjustment
may be required.
3.4 Tests
&
Adjustments
3.4.1 Preliminary
Verification
Before performing any adjustment, verify the per-
formance of the unit as shown in the Table 1
.
Important note: Before proceeding make sure that
the service monitor has been calibrated recently and
has warmed up for at least the time specified by its
manufacturer.
Some reported frequency and deviation problems
have actually been erroneous indications from serv-
ice monitors that have not adequately warmed up.
This is particularly likely when field service is done
during winter months.
3.4.2 Basic Tests & adjustments
Recommended Tests:
1.
TX power output
2.
Carrier frequency error
3.
Frequency deviation
Note: Only if a loss in system performance has
been detected, RX SINAD and RX audio
distortion should be verified.
Adjustments:
1.
Transmitter power output
2.
Frequency error
3.
Transmitter deviation
3.4.3 Tests & adjustments Proce-
dure
Refer to the RSS help file for details &
parameter information.
1.
Connect the Gemini/PD main antenna con-
nector (or the auxiliary receiver) to the
TX/RX input of the service monitor using a
suitable length of 50 ohm cable.
2.
Connect the Gemini/PD to a suitable power
supply and adjust the supply voltage to 13.6
volts.
3.
Using a suitable 9 conductor straight RS-
232 cable, connect the Gemini port 1 to the
RS-232 port of a PC and run the Gemini
RSS program.
4.
Press
GET
to get the configuration of the
unit.
5.
Refer to “
Tests and Adjustments
” table.