by Peter Parker VK3YE - first appeared in Amateur Radio, December 1998
Introduction
Most articles and handbook chapters on
mobile operation concentrate on operating from private cars and boats. They
normally assume that it is possible to mount a fairly efficient antenna outside
the vehicle. Users of public transport do not usually have this luxury.
Nevertheless, it is possible to enjoy amateur radio while travelling in trains,
trams, buses and ferries. This article tells you how. It's based on personal
experience gained from operation on trains, trams and buses in three states.
Advantages and disadvantages
Operating from public transport has a number
of disadvantages compared to transmitting from a car. These include the need to
carry your own power source (instead of relying on the car battery), the lower
transmit powers possible from hand-carried transceivers and the difficulty of
erecting antennas outside the vehicle. All this means that a portable station
in a bus or train carriage will have a lesser range than a mobile station.
However, this type of operation has
advantages too. Not having to concentrate on the road and having both hands
available means that using and adjusting equipment is easier. The greater
height of coaches (compared to cars) means that in-coach antennas operate
better than might be expected. The risk of being stopped by police for
operating a mobile transceiver is eliminated and the novelty factor of working
a train or bus mobile station increases the number of contacts obtained.
There are some differences between operating
in urban and rural areas. In cities there will often be a choice of repeaters
to use if the signals into one are marginal. In contrast, when travelling
through the country, there will be times when no repeater at all is
triggerable.
Repeaters may be located in a poor position
relative to the railway or coach route, or be at some distance from the route
taken. In such cases, there may be coverage for only a 10 or 15 km stretch of
the road or track before the repeater becomes inaccessible. At other times,
much longer distances are easily covered - for example with 2.5 watts and a
dipole antenna, it was possible to access the 6950 Mt Ginini repeater from
Cootamundra - some 120 kilometres away. Such distances are not common - ranges
of 15 to 30 kilometres are more usual.
Provided that you can access a repeater,
contacts are possible over the repeater's entire coverage area. The longest
distance contact made from a train by the author was a South Australian station
who was worked when the Melbourne-bound XPT train was approaching Wagga. The
contact was possible due to a sporadic-E propagation opening.
Equipment
The author has taken some or all of the
following on trips made:
Any two metre or two metre/seventy
centimetre handheld would be a good choice for the transceiver. A rig with a
wideband VHF/UHF receiver is best for tuning around in areas where no amateur
repeater is within range. Buy the matching headset or plug in your own
earphones to avoid disturbing other passengers.
Some hand-held transceivers come with a
choice of several battery packs to provide for different transmit power
settings. An RF output power level of 5 watts or so is desirable, particularly
in rural areas, to maximise transmitting range. However, a trade off has to be
made between talk time and power output. NiCad battery packs are usually adequate
for short trips. A 12 volt sealed lead acid battery (3 to 7 AH) is better for
longer journeys. See your transceiver's operating manual for advice on
connecting your rig to an external 12 volt battery. When it's not convenient to
carry such batteries and chargers, alkaline dry cells are highly recommended.
These are expensive but can provide hours of reliable operation on long trips.
For best results, use an antenna better than
the standard helical supplied with most hand-helds. A vertical dipole made from
RG58 coaxial cable is compact, flexible, quick to make and delivers good
performance from a coach or train carriage. Suction cups should be used to
attach the antenna to the inside of the window, perhaps concealed behind a
curtain. Constructional details of such an antenna appeared in a previous Novice
Notes and can be found on Novice Notes Online.
Operating
Most contacts will be on FM. This is because
of the greater activity on FM and the existence of repeaters. The vertical
polarisation that FM operators use also helps because vertical antennas are
easier to erect in a coach or train carriage than the horizontal antennas that
SSB operators use. However, having said this, mobile SSB operation is always
interesting and allows greater range than FM simplex. The ability to tune
around for beacons (ranges of 60 - 120 km are typical) is another benefit of
carrying SSB gear. If you do go SSB mobile, tell others about your trip and/or
arrange times for local operators to listen for you to maximise the possibility
of making contacts.
You should know the locations of repeaters
along your route before setting off. A repeater list, such as in the WIA
Callbook 99, and a good map (showing mountains) is useful here. Make a list of
repeaters within 50 or 100 kilometres of your route and try accessing them as
you travel along. Always use the actual location of the repeater (usually a
mountain) rather than the nearest big town by which repeaters are often
referred - the repeater may be some distance from the town and not be easily
accessible from within the town itself. Information on the locations of
repeaters is also important when deciding on which side of the train carriage
or coach to sit - if there's a choice, get a window seat facing the direction
of most repeaters that you wish to use.
Even quite large towns may have repeaters
that are accessible with a 25 watt mobile station, but not with a 2 watt
handheld in the town centre. The author has found that calling on 146.500 MHz
is sometimes successful. Provided the other station has a good antenna, simplex
contacts from a coach lasting 20 or more minutes are possible, especially if
traffic congestion is reducing travel speed. Simplex operation is also
practical in capital cities such as Melbourne, where the terrain is flat.
Receiving
When it is not possible to trigger repeaters
or obtain simplex contacts, its interesting to see what can be received from
inside a bus or train carriage. In such situations, a scanner and/or HF
receiver is useful.
Receiving beacons on the low end of two
metres has already been mentioned. Use an SSB receiver for best reception.
Those without an SSB receiver could try tuning in to the Morse practice beacons
that operate in some cities. Able to be received on a standard FM transceiver,
their range can be considerable.
Below the AM broadcast band operate low
frequency beacons for aircraft navigation. These transmit a Morse Code
identification and, sometimes, weather bulletins. In most areas, several of
these should be audible.
If you can extend the telescopic whip of
your short wave receiver, it may be possible to pick up foreign broadcast
stations, especially if travelling in a coach or bus. The time of day is
important - around noon you may not hear anything, but signals improve by the
early evening. Reception of stronger HF amateur signals may also be possible,
depending on band conditions.
Many VHF/UHF amateur transceivers include
extended coverage VHF/UHF facilities. This allows reception of commercial and
other two-way radio traffic. Either program several known active frequencies
into the memories or use the radio's scan feature.
The main problems encountered when trying to
use a receiver in a train, tram or bus are noise and shielding caused by the
vehicle's metal body. Both trains and coaches can generate noise, but this
usually is not serious, at least on VHF. However, trams can be a noisier
receiving environment. Shielding of signals is not usually a severe problem on
a bus or coach, especially if it has large windows. Trains are significantly
poorer RF environments than buses, and reception of LF, MF and HF signals is
usually non-existent unless the signal is very local. Interestingly, VHF radio
reception is usually quite good on a train. Whatever vehicle you are in, placing
the receiver near the window usually improves signal strength.
Other Activities
This article has concentrated on voice
repeater and simplex operation. However, other modes may be possible whilst bus
or train mobile. Packet (in conjunction with a laptop computer) and CW offer
the advantage of not requiring a microphone (thus drawing less attention to
oneself). However, packet requires stronger signals than FM voice, and is prone
to frequent disconnects. CW operation would allow longer transmitting ranges
than SSB or FM simplex. However, the lack of activity means that you would need
to arrange skeds with operators along your route beforehand.
Contesting is another activity that should
be practical from a bus or train. Those contests that have high local VHF
activity combined with credit for repeat contacts (such as the Remembrance Day)
would be well suited to this type of operation. Travel on the major rail lines
or bus routes would place you within easy simplex range of most operators at
some time during the contest period. Routes that produce the most contacts
could be travelled along every few hours to maximise the number of repeat
contacts. The purchase of a daily or weekly ticket is suggested to keep the
fares incurred by this amount of travel low.
Further reading: VK3JED's amateur radio on
public transport webpage.
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This page was produced by Peter Parker VK3YE parkerp@NOSPAMalphalink.com.au. Material may be copied for personal or non-profit use only.