___________________________________________________________
Page 4-20
GNS 400W Series Maintenance Manual
Rev. A
190-00356-05
4.5
COMM BOARD TESTS
This section lists the test procedures for the comm board. The transmitter tests are described first
followed by the receiver tests.
Test Equipment
Standard shop avionics test equipment can be use to test the unit.
Test Setup
The test setup is designed and supplied by the avionics shop.
4.5.1 Standard
Loads
Antenna
The comm radio operates with a conventional 50 ohm vertically polarized comm radio antenna.
The comm transmitter is terminated into a 50 ohm resistive load capable of dissipating a
minimum of 50 watts and with a VSWR of no greater than 1.2:1.
Audio
The standard audio load is 500 ohms between COMM AUDIO HI J2-7 and COMM AUDIO LO
J2-19.
4.5.2 Standard
Signals
RF Level Units
All specifications given for the comm radio are in HARD units. To arrive at these units
adjust the RF generator to the level specified and insert a 6 dB pad at the output of the RF
generator.
Standard Microphone Input Signal
A 1000 Hz tone with 275 mVrms into a 500 ohm load.
Manufacturer’s Rated Audio
Manufacturer’s rated audio is the rated output power that the receiver is capable of delivering to
one standard comm radio audio output load. This is defined as 100 mW delivered to a 500 ohm
load (which corresponds to 7.07 Vrms across that load).
Closed Squelch
The condition of the squelch in which audio is suppressed.
Open Squelch
The condition of the squelch in which audio is not suppressed.