Northern Airborne Technology RA Series - Manual (Page 4)

RA Series Remote Attenuator
SM30 Installation and Operation Manual
Section 1 Rev: 1.00 Issue 4 Page 1-1
ENG-FORM: 800-0114.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.
Section 1 Description
1.1 Introduction
Information in this section consists of product description, design features and specifications for the RA
Series Remote Attenuator. All derivative product information shall be contained in the applicable manual
supplement, which may be obtained from NAT as required.
Review all notes, warnings and cautions.
1.2 Product Description
The RA-series of remote attenuators reduce the RF transmit power from a transceiver under logic control
from a Tac/Com control head or a switch. The attenuator may also be enabled and perform the same
function during receive operations. The attenuator is normally enabled when the control line is unactuated
(not grounded). A ground (<1 Vdc) on the control line will bypass the attenuator and allow RF to pass at
full power. When enabled, the remote attenuator will reduce the incoming signal by a factor of 10
(RA10-xxx) to 1000 (RA30-xxx). There is a remote attenuator model that can handle up to 1 W
continuous power (RAxx-001) and another model that can handle up to 20 W continuous (RAxx-020).
The RA series Remote Attenuators are bulkhead mounted units specifically designed to allow attenuation
of aircraft radio transmissions. This is desirable under some conditions where the radio exceeds output
power limits of altitude. If the radios were simply adjusted to output the lower level, they may become
unstable and difficult to control tightly to the output tolerances. By installing a RA series Remote
Attenuator, radio operation is not impaired and the required output power is achieved.
RA units also normally attenuate the receive signals to reduce some channel interference from nearby
stations when at altitude.
1.3 Design Features
RA series Remote Attenuators are easy to install with an uncomplicated interconnect.
They are powered from a +28 Vdc aircraft supply and available in a variety of configurations.
A ground seeking keying circuit enables RF signals to pass either attenuated or unattenuated.
All interconnect and relay contacts are gold plated. The relays are sealed, high vibration rated (50g
shock), dry nitrogen filled.
The circuit boards are constructed of G10-FR (flame retardant) material, with solder masks reflowed tin
plating and environmentally post-coated.