Our airfield has just been assigned its own frequency 118.275 MHz, with
associated
8.33 Khz channel number 118.280. Club members queried the numerical difference,
so herewith a short list of VHF radio frequencies and their corresponding
channel numbers. This was created by way of explaining why Longside airfield
has been assigned Channel 118.280, yet will operate on frequency 118.275 MHz.
The old 25 KHz separated frequencies are shown in bold and it should be
appreciated
that while a new 8.33 KHz aircraft radio is capable of operating on the old
frequencies, when in 8.33 mode the bandwidth of those oldfrequencies has been
narrowed to enable two new 8.33 frequencies to be inserted betweeneach pair
ofold ones. There is a penalty for narrow bandwidth, which is that speech
quality
is a bit poorer.
If someone were to transmit using the old 25 KHz frequencies, communication
would
still work but the wider bandwidth would spill over and interfere on adjacent
8.33 KHz channels.
To discriminate between the old 25 KHz frequencies and their corresponding new
8.33 channel numbers, radio manufacturers have added a '5' or a '0' in the third
decimal position on the aircraft radio display. This is why, as an example,
it is possible to mistakenly select channel 134.105 and yet still be able to
communicate with Aberdeen Offshore which continues to operate on frequency 134.1
MHz. The result is a slight "mismatch" with poorer comms for both parties,
which someone more knowledgeable would be able to explain.
So when ATC gives you an instruction to change to Radar 119.055, you probably
won't
hear the word 'frequency' mentioned. On the other hand it would be correct
to say "Change to frequency 134.1" because that isn't an 8.33 channel number.
But in practice nobody's likely to be shot down in flames for misusing such
terminology.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=490464#490464
Attachments:
http://forums.matronics.com//files/frequency_and_channel_115.pdf
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