Avionics News January 2023 - 56

THEORY & PRACTICE
Continued from page 55
ocean may be equipped with an HF
communication system.
In contrast to VHF
communication, HF systems are
not channelized. Instead, most can
receive and transmit on the entire
HF spectrum. The flight crew is
responsible to choose the appropriate
frequency, for example, 4.675 MHz
for the North Atlantic. Although
many HF systems have the ability
to transmit and receive AM, the
normal mode of operation is single
side band, specifically upper side
band. Refer to the October 2022
issue of this publication for a
description of SSB.
AVX-10K
COMMUNICATIONS,
NAVIGATION &
SURVEILLANCE
FLIGHT LINE TEST SET
From a simple system auto-test, to in-depth
troubleshooting, quickly perform testing
around the aircraft or in the cockpit using
your mobile device.
viavisolutions.com/avx-10k
56 avionics news * january 2023
HF communication presents a
challenge to aviation due to antenna
size requirements. A Marconi-style
antenna for 4.675 MHz would be
52 feet in length. Another aviation
HF channel is on 13.282 MHz,
and an appropriate antenna for
this channel would be about 18.5
feet in length. Thus, two problems
comprise the challenge. First, the
antennas required are too long to be
practical, and second, the antenna
length requirements vary greatly.
To overcome the antenna
challenge, engineers design
couplers, which will add
inductance and capacitance as
necessary to allow power transfer
to the antenna, which is too short
for the frequency being used by the
flight crew. A brief transmission
(clicking the push-to-talk button)
will start a tuning cycle. Once
the tuning cycle is complete, the
flight crew will be able to use the
transmitter. The coupler may be a
remotely mounted unit or be part
of the antenna itself.
HF antennas for aircraft vary
widely. They may be of the long
wire type, stretching from the
forward fuselage to the tail, or
they may be of the probe type,
which looks like a long horizontal
mast. Popular on many jets is a
short wire, which makes the entire
airframe into an HF antenna.
One may wonder why owners
use an HF system when several
satellite systems are available.
Mainly, this is a cost consideration.

http://viavisolutions.com/avx-10k

Avionics News January 2023

Table of Contents for the Digital Edition of Avionics News January 2023

Avionics News January 2023 - Intro
Avionics News January 2023 - Cover1
Avionics News January 2023 - Cover2
Avionics News January 2023 - 1
Avionics News January 2023 - 2
Avionics News January 2023 - 3
Avionics News January 2023 - 4
Avionics News January 2023 - 5
Avionics News January 2023 - 6
Avionics News January 2023 - 7
Avionics News January 2023 - 8
Avionics News January 2023 - 9
Avionics News January 2023 - 10
Avionics News January 2023 - 11
Avionics News January 2023 - 12
Avionics News January 2023 - 13
Avionics News January 2023 - 14
Avionics News January 2023 - 15
Avionics News January 2023 - 16
Avionics News January 2023 - 17
Avionics News January 2023 - 18
Avionics News January 2023 - 19
Avionics News January 2023 - 20
Avionics News January 2023 - 21
Avionics News January 2023 - 22
Avionics News January 2023 - 23
Avionics News January 2023 - 24
Avionics News January 2023 - 25
Avionics News January 2023 - 26
Avionics News January 2023 - 27
Avionics News January 2023 - 28
Avionics News January 2023 - 29
Avionics News January 2023 - 30
Avionics News January 2023 - 31
Avionics News January 2023 - 32
Avionics News January 2023 - 33
Avionics News January 2023 - 34
Avionics News January 2023 - 35
Avionics News January 2023 - 36
Avionics News January 2023 - 37
Avionics News January 2023 - 38
Avionics News January 2023 - 39
Avionics News January 2023 - 40
Avionics News January 2023 - 41
Avionics News January 2023 - 42
Avionics News January 2023 - 43
Avionics News January 2023 - 44
Avionics News January 2023 - 45
Avionics News January 2023 - 46
Avionics News January 2023 - 47
Avionics News January 2023 - 48
Avionics News January 2023 - 49
Avionics News January 2023 - 50
Avionics News January 2023 - 51
Avionics News January 2023 - 52
Avionics News January 2023 - 53
Avionics News January 2023 - 54
Avionics News January 2023 - 55
Avionics News January 2023 - 56
Avionics News January 2023 - 57
Avionics News January 2023 - 58
Avionics News January 2023 - 59
Avionics News January 2023 - 60
Avionics News January 2023 - 61
Avionics News January 2023 - 62
Avionics News January 2023 - 63
Avionics News January 2023 - 64
Avionics News January 2023 - Cover3
Avionics News January 2023 - Cover4
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