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If you have an old VHF radio, and you wouldn’t be alone
considering almost half of the General Aviation fleet in
Australia is more than 31 years old, you may be forced to
upgrade. Soon, in fact.
Airservices Australia is responsible for assigning VHF
aeronautical frequencies in Australia. Due to increasing
number of frequencies being assigned they are struggling to
continue to find interference-free frequencies for use in high
traffic areas. To overcome the problem frequency spacing has
been reduced from 50khz to 25khz.
We have been warned this was coming. In September 2005
Airservices Australia and CASA told us about the pending
changes in AIC H11/05. There was also an article in Flight
Safety Magazine (Channel Squeeze) around the same time.
At the time, the real effect was too far in the future for most
pilots and owners to worry about. The first to be affected was
the high-flying IFR traffic in Class A Airspace (Nov 2005), next
in line in November 2006 was Class C, D and E airspace
users in high density traffic areas. There are relatively few
frequencies at 25khz spacing, so you may not have needed
to use any yet. Is it something you check during flight
CAO 103.25 (receiving) and CAO 103.24 (transmitting) tell us
“The frequency range and number of channels must be
adequate for the intended operational purpose of the
equipment” which means, if you don’t need to use a 25khz
spaced frequency, you don’t need to have a radio capable of
transmitting and receiving at 25khz spacing. That’s a relief.
So, all you need to do is check your charts before you go,
and as long as there are no tricky frequencies (118.02,
134.32, etc) along the way, you can continue to fly with your
This will continue to be the case; however, it is going to
become more difficult to practice. Bruce Bilton, CTAF
frequency assigner at Airservices Australia, has advised that
in high density areas 25khz spacing of CTAF frequencies is a
year away at the most. Anyone flown at Kyneton and heard
aircraft at Geelong and Barwon Heads? It can get busy and
confusing at times with these areas sharing a frequency.
So if you fly at CTAFs around the major east coast cities, it is
highly likely you are going to be affected by the new
frequency spacing in the next year or so.
Let’s get clear on who has to do what.
If your VHF radio displays 3 decimal places, e.g. 118.025 can
be dialled up and displays on your radio, you are not affected;
your radio supports 25khz spacing.
If your VHF radio displays 2 decimal places you need to
check if you can dial up frequencies like 118.02, 118.17. If
you can, that’s great, you are not affected.
If your VHF radio goes straight from 118.00 to 118.05 when
you turn the knob, you have a 50 khz antique and this article
was written for you, read on.
The next thing to do is consider the area you operate in.
Anyone regularly flying in controlled airspace or flying IFR
should already have upgraded, but if your home base is
Broken Hill, and your biggest cross country is to Menindee to
see a mate, you will probably not need to take any action at
all. If you operate in the maze of CTAFs on the outskirts of
Melbourne or Sydney, or in South East Queensland, you
should plan an upgrade soon.
An upgrade shouldn’t be too heart-breaking if you are
constantly having problems with your old radio. They are
expensive to repair these days, and once they start to have
problems it is usually the beginning of the end.
For VFR aircraft, a new, non-TSO’d radio can be bought for
under $2000. For IFR aircraft a TSO’d radio is needed, and
these start at about $5000. In order to install a new radio (or
anything new) in a certified aircraft you will need CAR 35
approval. This is where it starts to add up. You need design
drawings to show how the radio will be mounted, a wiring
diagram, an electrical load analysis and weight and balance
change calculation. Once the CAR 35 approval is received,
the installation begins. Removal of the old radio, manufacture
of mounting brackets, wiring new radio, materials and a
possible new antenna all add up. You would need to budget
at least another $2000 for the installation and associated
approvals and documents. If you are considering upgrading
anything else in your panel, this would be the time to have it
done as the installation cost should only increase slightly for
each new item installed at the same time (of course, the
purchase of the new gear could easily blow the budget).
If you have one of these antique radios and can’t bear to part
with it (it works perfectly – why throw it away?) you could
consider having a more modern radio installed as a second
radio. Two radios are really quite useful, and it won’t matter if
only one of them is capable of the 25khz spacing. You may
have to factor in the additional cost of an audio selector
In the information issued in 2005 regarding changes to
frequency spacing, there was mention of CASA introducing
new frequency stability requirements of 0.003% from
November 2009. That would mean that even if you could get
by with your old radio with 50khz spacing in your operations,
your radio would have to comply with the new requirement
(which stops transmissions from ‘spilling’ over and jamming
adjacent frequencies). Many of the older radios would be
unable to comply, and therefore no longer be approved for
use. No NPRM has been issued by CASA on the proposal
and current information suggests this won’t be happening
now. AIC H03/09 is the latest information on the topic,
issued by Airservices Australia. They have confirmed
upgrade of equipment is not mandatory, and only required if
25khz spacing is needed for your particular area of
Changes to VHF Channel Spacing
More equipment upgrades for flying Friends?
Aerogram December 2009
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