MicroAir Avionics M760 - Noise Suppression Techniques; Power Filter for Noise Reduction; Ferrite Chokes for RFI Reduction

Microair Avionics M760 Transceiver Installation & User Manual
M760Q Install & User Manual 01R12.doc Page 17 of 36 30
th
March 2010
3.14 NOISE SUPPRESSION
After installation there may be unwanted noise present in the radio’s audio system. There a variety of
sources for this noise, but they usually fall into one of two categories:
 Electro-Magnetic Induction (EMI)
 Radio Frequency Induction (RFI)
3.14.1 POWER FILTER
EMI typically affects radio equipment by inducing noise on to the
power supply. Microair recommends the installation of a power
filter on the power wire to the M760. A simple line filter is
sufficient to ensure that the voltage is smooth, and causes no
interference to the radio. If engine noise can be heard, and it rises
and falls with the RPM, install a power filter.
Refer to the Microair Avionics website www.microair.com.au
for
more information on aircraft electrical systems.
3.14.2 FERRITE CHOKES
RFI typically affect radio equipment by radiating RF noise into
the wiring. The most vulnerable are the microphone, headphone,
speaker, and power lines. The instance of RFI can be reduced by
installing ferrite chokes on the wiring harness.
Locations for best effect are on the wiring
harness immediately behind the DB15
connector at the radio, and on the
microphone/headphone lines just behind the
headset jacks.
Another form of RFI is the impulse noise from equipment like strobe lighting. This
equipment can create large impulses on the power supply which have RF
components.
These signals can radiate to adjacent wiring to create noise. The best defence here
is a filter capacitor on the power input to this type of equipment. A 0.01uF ceramic
capacitor with a 3KV voltage rating is most suitable for this task.
Refer to the Microair Avionics website www.microair.com.au
for more information on aircraft electrical
systems.