australia:radio
radio for campers
Introduction
there are a variety of radio devices available depending upon needs:
for those going off-grid or for when the internet / mobile phone system goes down such as extreme weather events (strong winds, floods or bushfires knocking out the local electricity grid) it is nice to have other options such as radio which does not rely upon local infrastructures
radio may be the ONLY way of communicating to the outside world in a disaster
effect of solar storms on SW radio:
in general, SW reception is best in periods when solar activity cycle is at its peak due to a longer term strengthening of the F layer in the ionosphere which the SW bounces off EXCEPT when there is an actual solar storm hitting earth.
solar storm activity increases the density of the ionosphere and whilst this will improve reflectivity from the F layer, but it also increases the density of the D layer through which the shortwaves must pass TWICE hence a solar storm hitting earth will generally cause a short-wave fadeout (SWF) or sudden ionospheric disturbance (SID) especially at lower frequencies (especially 5MHz which may be totally blocked, while a moderate effect may be on the 10MHz region where most international broadcasts occur).
These Fadeouts mostly have a rapid onset of a few minutes as solar storm hits and a slower recovery lasting perhaps an hour although this is highly variable. The high frequencies (eg. 20MHz) are the last to be affected and the first to recover.
NOTE: the HF circuit is affected ONLY if there is an ionospheric reflection point for the signal in the sunlit hemisphere - it will not occur if that reflection point is in the dark.
1)
Types of radio transmission
Radio frequency bands
long wave (LW)
100-519kHz
transmitters require a tall radio mast and carrier frequencies are exact multiples of 9 kHz;
used for broadcasting only within ITU Region 1 including Europe, Russia, Nth Africa
long-wave signals can travel very long distances up to 1000s of kms
medium (MF or MW)
300 – 3000 kHz with wavelength of 1000–100m
transmitters require a tall radio mast
in this band the signal to noise ratio is determined by atmospheric noise not receiver antenna size and thus radio receivers can use small ferrite rods for this band
mostly used for AM radio broadcasting (usually 526.5 kHz to 1606.5 kHz), navigational radio beacons, maritime ship-to-shore communication, and transoceanic air traffic control.
high (HF) or "shortwave radio"
3 – 30
MHz with wavelength of 100–10 m
most transmitters use AM mode and all use
UTC time
best listening is usually at night pending path of the radio waves
Single Side Band (SSB) is used by hams and many utility stations and for Morse Code (CW)
radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere – a method known as “skip” or “skywave” propagation – these frequencies are suitable for long-distance communication across intercontinental distances and for mountainous terrains which prevent line-of-sight communications
maximum usable frequency regularly drops below 10
MHz in darkness during the winter months, while in summer during daylight it can easily surpass 30
MHz.
when all factors are at their optimum, worldwide communication is possible on HF.
most common antennas in this band are wire antennas such as wire dipoles and the rhombic antenna, and for receiving, random wire antennas are often used.
used by:
-
very high (VHF)
30 – 300
MHz with wavelength of 10–1 m
VHF is the first band at which wavelengths are small enough that efficient transmitting antennas are short enough to mount on vehicles and handheld devices
VHF signals propagate under normal conditions (excluding mountainous areas) as a near line-of-sight phenomenon:
used for:
Digital Audio Broadcasting (DAB) radio (channel blocks 9A, 9B and 9C)
FM radio broadcasting (88.1-108.1MHz)
television broadcasting (VHF Band I was used for the transmission of analog television)
two-way land mobile radio systems (emergency, business, private use and military)
air traffic control (118-137MHz)
long range data communication up to several tens of kilometers with radio modems
amateur radio (50-54MHz 6m band and 144-146MHz 2m band)
Radionavigation 60: 84–86
MHz
Fixed Maritime Mobile: 130–135.7
MHz
Fixed Aeronautical radio navigation: 160–190
MHz
Broadcasting Aeronautical Radionavigation: 255–283.5
MHz
Aeronautical Radionavigation AUS 49 / Maritime Radionavigation (radiobeacons) 73: 315–325
MHz
ultra high frequency (UHF)
300 – 3000
MHz with wavelength of 100–10 cm
propagate mainly by line of sight
they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception.
atmospheric moisture reduces, or attenuates, the strength of UHF signals over long distances, and the attenuation increases with frequency.
occasionally when conditions are right, UHF radio waves can travel long distances by tropospheric ducting as the atmosphere warms and cools throughout the day.
radio repeaters are used to retransmit UHF signals when a distance greater than the line of sight is required.
antennae can be 2.5-25cm long and the short wavelengths also allow high gain antennas to be conveniently small.
used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, CB radios
UHF radar band are frequencies between 300
MHz and 1
GHz plus the L band between 1 and 2
GHz and the S band between 2 and 4
GHz
in Australia:
UHF citizens band (Land mobile service): 476–477
MHz consisting of 80 channels:
-
fixed point-to-point Link 450.4875 - 451.5125
MHz
land mobile phone service 457.50625 - 459.9875
MHz
mobile satellite service: 406.0000 - 406.1000
MHz
Wi-Fi operates at 2412
MHz-2484
MHz
-
super high frequency / microwave
-
small wavelength allows them to be directed into narrow beams via parabolic dishes hence often used for data links
propagate solely by line of sight;
create strong reflections from metal objects the size of automobiles, aircraft, and ships, and other vehicles hence used in radar
UHF CB Radios
NOT useful for emergency communications due to limited coverage
generally not worth carrying while hiking, except for group management purposes
they are popular with 4WD convoys and for groups of hunters
these generally are rated for line of sight coverage
CB UHF uses frequencies around 27MHz and now has 80 channels available (used to be only 40), in Australia:
channel 8: 27.055MHz highway channel
channel 9: 27.065MHz emergency channel
channel 11: 27.085MHz AM call channel
channel 16: 27.155MHz LSB call local
channel 35: 27.355MHz LSB call DX
5W is the most powerful you can usually buy and generally will get you up to 17km line of sight but they are bigger, heavier (almost 1kg each), use more battery power than 2W versions
you can also get UHF radios with GPS capability such as:
the
Garmin Rino 750 - this can show each party with such a device the location of other party members whilst allowing 5W UHF radio communication up to 32km line of sight, and a longer battery life than most smartphones especially in cold weather, plus it is USB chargeable so a USB power pack will allow extra usage. Note though that topographic maps are an extra cost ($A99-199) and must be purchased separately for EACH device, and map updates are not free!
General Mobile Radio Services (GMRS)
Software Defined Radio (SDR) receivers
NB. HF requires a different antenna (and potentially, attachment to the AirSpy Spyverter to access frequencies < 35MHz) to VHF/UHF and thus you either need a dongle with dual antenna inputs or you need a manual low-loss coaxial switch.
use a USB dongle (with analog-digital converter) to connect to a computer and to a dipole antenna
requires special software such as:
see Youtube articles:
Portable SW radio receivers
may be the only communication options if the internet and satellite comms go down as with a major solar storm, major disaster such as bushfires/floods or IT warfare
for campers out of mobile phone coverage range, in addition to keeping in contact with local and nationwide / global news, you can access weather including weather faxes (wefax) of weather maps (just needs audio cable from radio to your laptop and software to decode the fax)
avoid cheap models
good models are:
-
stereo speakers which can be used via USB as PC speakers
microSD card slot to play music
1kg; two 18650 lithium batteries, with separate charging capability.
$AU490
-
-
one USB chargeable lithium battery
best sound for the era but bettered by Tecsun's 2020 models
covers the entire shortwave range (100-29999KHz), Longwave, FM and AM broadcast bands
1.5kg
$AU275
C Crane CC Skywave Shortwave Portable Travel Radio
Eton Grundig Satellit 750 Ultimate
no battery, needs 6V input
taps into the aircraft band from 118 to 137MHz but unfortunately lacks the weather frequencies, making it unsuitable for an emergency radio that receives NOAA stations.
Sangean ATS-909X World Band Receiver
Feature | Tecsun H-501 | Tecsun PL-990 | Tecsun PL880 |
price | $AU490 | $AU475 | $AU275 |
released | 2021 | 2020 | 2014 |
weight | 1kg | 0.62kg | 1.5kg |
size | 277 x 167 x 44mm | 198 x 120 x 38mm | 240 × 160 × 70 mm |
speakers | 6Ω, 3W x 2 stereo | 4Ω, 3W single | single |
USB PC speaker mode | yes | no | no |
bluetooth | no? | can use radio as BT speaker | no |
microSD slot music | yes | yes | no |
alarm clock | yes | yes | yes |
USB chargeable lithium battery | two (2nd as spare) x 18650 selectable | one 18650 | one 18650 |
DC input power | DC 5V/1A power adapter | | |
SSB | yes, USB/LSB | yes, USB/LSB | yes, USB/LSB |
Amateur Ham radio transceiver equipment
HF transceiver
antenna tuner
antenna
other equipment needed
australia/radio.txt · Last modified: 2021/08/18 18:55 by gary1