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noelf

Well Known Member
In the US, we have com frequencies spaced 25khz apart, such as 123.000, 123.025, 123.050, 123.075, 124.000, ...,. Some radios display all three digits to the right of the decmal, others show only two digits.

How are the frequencies displayed in the com radios with the 8.33 kHz spacing?
 
The key is there will be 'channels' with 'names', so rather than dialling up the frequency you will communicating on you dial up the 'channel'.

So the 25kHz freq might be 128.0, dialling up this frequency will have the radio working in 25kHz mode.
The same frequency can be used in 8.33 land, except the channel is called 128.005, and that is what you dial up on the radio.
128.00833 MHz is called 128.010
128.0167 MHz is called 128.015 (there is no channel called 128.020)
128.025 MHz is a 25kHz frequency, the paired 8.33 channel is 128.030 - that is the radio is using 128.025 MHz but working in 8.33 kHz mode. And so on.

Clear as mud - it usually takes 3 or 4 reads to understand what is going on!!

Most radios can switch between 25 & 8.33kHz modes, so currently its is not required to skip through all of the un-used channels. Until 2017 8.33 is only supposed to be in used high up. However, airfields have to pay for their frequencies here by the bandwidth they use (completely daft concept), so some are keen to move to an 8.33 frequency and reduce their bill by 2/3.

Pete
 
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