Northern Airborne Technology NTX - Manual (Page 23)

SM28 Rev. 4.10 NTX VHF-FM Series Remote Mount Transceivers Manual
Avoid sharp bends in the coax cables (minimum 3" radius) to prevent severe reflections.
If sharp bends are required use 90
° elbow adapters.
Fabrication and installation of wiring harness should be in accordance with the original
aircraft manufacturer’s maintenance instructions or AC43.13-1B Change 1, chapter 11,
sections 5 to 13, 16 and 17.
Grounding and bonding should be in accordance with the original aircraft manufacturer’s
maintenance instructions or AC43.13-1B Change 1, chapter 11, section 15.
2.3.5 Antennas
Correct antenna placement and mounting is critical in order to achieve the best possible
performance. In general, keep all antennas as widely separated as possible and clear of
any large airframe obstructions. Avoid any placement that puts antennas of like
frequencies close together.
Installation of the antenna should be in accordance with the aircraft manufacturer’s
instructions for continued airworthiness or AC43.13-1B Change 1, chapter 11, section
15 and AC 43.13-2A chapter 3. If possible, the antenna should be located a minimum of
12 ft from aircraft navigation receiver antennas and a minimum of 4 ft from aircraft
communications and ELT antennas. Be careful not to choose separations that closely
approximate ¼, ½ or whole number multiples of the navigation or communication
system wavelengths.
Bottom mounted antennas will perform best in flight, but poorest on the ground during
testing. Antennas may be severely degraded by 'masking' effects of the fuselage or
stabilizers, and generally give best performance when bottom mounted.
Surround any blade or whip antenna with a ground plane surface (metallic, grounded
material) having a radius equal to or greater than the height of the antenna. Poor
grounding will result in severe reflected power and high levels of RFI throughout the
airframe.
Any antenna will be less prone to interference from rotor modulation and other undesirable
stimuli if installed correctly and surrounded by a large metallic ground plane. Under the
same conditions, it is also much less likely to cause interference to other aircraft systems
(e.g., coupling into audio system, fluctuations in instrumentation, etc.). Poor grounding will
result in severe reflected power and high levels of RFI throughout the airframe.
Avoid antenna locations that will become fouled with oil, water, fuel or dirt as this will
degrade performance. Roof mounts (in close proximity to rotor blades) are permissible.
2.3.6
Mechanical Mounting
Installation of the transceiver should be in accordance with the aircraft manufacturer’s
instructions for continued airworthiness or AC 43.13-1B Change 1, chapter 7, sections 2
to 7, and AC 43.13-2A chapter 2.
Jun 1, 2004 Page 2-3
ENG-FORM: 805-0108.DOT
Amendment # 3 Jan 14, 2008
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.