Installation manual

Installation
Apollo GX50/60/65 Installation Manual
27
d) Repeat for additional frequencies as follows.
121.125 MHz 131.225 MHz
121.175 MHz 131.250 MHz
121.200 MHz 131.275 MHz
121.225 MHz 131.300 MHz
121.250 MHz 131.325 MHz
131.200 MHz 131.350 MHz
e) Repeat for each comm transmitter.
f) If the GX50/60/65 is susceptible to VHF comm transmitter interference, then better
isolation, or distance, may be required between the GPS and VHF antennas. With
some comm transmitters, a notch filter may be required in series with the VHF
comm antenna coax at the rear of the comm unit.
Note: Older VHF comm transmitters may emit higher levels of harmonic interference
causing greater problems and may be more difficult to deal with.
Interface Checks
The interfaces to other equipment, such as the SL40 or a moving map display, should be
checked. Refer to the GX50/60/65 user’s manual for this part of the checkout. Make sure the
other equipment is connected and switched on.
To check the serial data output connections, verify that the data from the GX50/60/65 can be
displayed on the other units, such as a moving map display or the SL40.
VHF COMM CHECKOUT (GX60/65)
Receiver / Transmitter Operation
Tune the unit to a local frequency and verify the receiver output produces a clear and
understandable audio output. Verify the transmitter functions properly by contacting another
station and getting a report of reliable communications. Check the remote flip/flop.
Antenna Check
The antenna VSWR can be checked using an inline wattmeter in the antenna coax using
frequencies near both ends of the band. The VSWR should be < 2:1, and is not to exceed 3:1.
A VSWR of 2:1 will cause a drop in output power of approximately 12%, and 3:1 causes
approximately a 26% drop.
Sidetone Level Adjustment
The sidetone volume was preset at the factory to a typical audio level. The level can be
adjusted using one of the built-in system functions. To adjust the sidetone level:
1. Press SYS, rotate the LARGE knob to the “COM INFO” page, and press ENT.
2. Rotate the
LARGE knob to the “SIDETONE LEVEL” page.
3. Press SEL, rotate the SMALL knob to adjust the sidetone level, then press ENT when
complete. The sidetone level is displayed in a range of 000 to 255, with 255 the highest
level. The sidetone level can be adjusted during transmit.
Comm Flight Test Check
A flight test is recommended as a final installation verification. The performance may be
verified by contacting a ground station at a range of at least 50nm while maintaining an