Northern Airborne Technology NT4xx - Manual (Page 16)

UHF Transceiver Manual SM04 Rev. 4.00
Page 2-6 Nov 27, 2003
ENG-FORM: 805-0106.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.
iii) Check pin 6 for PTT action (closure to ground when keyed), and pin 5 for
mic connection. Note that these are commonly reversed by accident, and will
result in transceiver keying, but no modulation.
iv) Check pins 11 and 24 for continuity to the ship's audio system as required
for RX audio.
d)
ENSURE that neither pin 12 or 25 is connected to ground, or immediate failure of
the radio will result. This (optional) speaker line is a bridge output, and must be
floating above the airframe ground.
e)
Ring out the channeling lines to the control head connector, and check for shorts
on all shielded cables. Note that a quick check of these lines will save many
wasted hours later, and possible control head and R/T damage.
f)
Check the RF connector for continuity to the antenna, and open circuit to ground
from the center conductor.
NEVER make a HI-POT test on this RF coax cable, unless the transceiver is KNOWN
TO BE DISCONNECTED. Failure to follow this information will result in a damaged
transceiver which is not covered by warranty!
DO NOT ATTACH THE TAC/COM TRANSCEIVER until the above conditions are met.
2.3.6.2 Performance
Checks
a)
Power up the ship's system with the Tac/Com control head and R/Ts installed,
and turn on all of the radios and other accessories required for this system.
b)
Check for correct radio operation and channeling, both receive and transmit, and
ensure that all status indications are correct (TX and SQ) Do not proceed until
the radios are operating correctly. You may have to set the DISPLAY
CONTRAST pot (on the LCD controls), or use the CONTRAST/BRIGHTNESS
screen (reached after the last radio with the "RADIO" button) to obtain a suitable
display.
c)
Check each antenna feedline at the R/T with a through-line wattmeter and
suitable frequency elements to ensure correct antenna matching. Reflected
power in excess of 25% represents a serious problem, and should be
investigated carefully, or serious RFI and system interference as well as possible
radio damage may result. Check that forward power is to specifications over the
required band, as specified for the radio in use.