Primarily for general aviation discussion, but other aviation topics are also welcome.
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By James Chan
#1657754
to 8.33kHZ channel on the same frequency.


It's not quite the same? You mean to the one nearest to the existing 25Khz frequency? :D
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By xtophe
#1657756
I mean the actual physical frequency at which the electrons wiggle is the same. The width of the channel has changed. Hence the name or numbers the channel is called is also changing. The fact that the name look like a frequency is another matter.
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By riverrock
#1657767
xtophe wrote:Special mention to Prestwick and Glasgow who don't know when they are changing despite having 1 year to prepare.

I understood that airports don't get a choice - its changed at licence renewal. They need to have either applied for an exemption (which seems to be a list of LARS services) or they will be changed.

There are still a fair number of airports missing
including:
Bournemouth
Carlisle
Coventry
Londonderry/Eglinton - EGAE
...
(I got bored at C)
By GAFlyer4Fun
#1657826
Just goes to show that if the authorities cant organise this to be completed in a year, it is no surprise the bigger authorities cant work out Brexit in 2 years :wink:
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By Iceman
#1657832
James Chan wrote:
to 8.33kHZ channel on the same frequency.


It's not quite the same? You mean to the one nearest to the existing 25Khz frequency? :D


Any 8.33 kHz channel that has a channel offset of 0.005 from its previous 25 kHz frequency, e.g., Blackbushe has gone from a frequency of 122.300 MHz to the 8.33 kHz channel 122.305, similarly xzy.a25 to xyz.a30, xzy.a50 to xyz.a55, and xzy.a75 to xyz.a80 has not changed frequency at all. All of these 8.33 kHz channels are using exactly the same frequency as they did before, e.g., Blackbushe is still radiating and receiving on a frequency of 122.300 MHz. The channel offset of 0.005 does not change the frequency by an increment of 8.33 kHz, it merely instructs the transceiver to limits its transmit and receive bandwidths to an 8.33 kHz channel spacing based on the 25 kHz frequency.

To get a genuinely new frequency in 8.33 kHz land, you'd have to be using one of the new 0.010 or 0.015 channel offsets from a 25 kHz frequency designator, the new frequencies then being 8.33 kHz and 16.66 kHz offset from a 25 kHz frequency.

Iceman 8)
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By chevvron
#1657854
Iceman wrote:
Any 8.33 kHz channel that has a channel offset of 0.005 from its previous 25 kHz frequency, e.g., Blackbushe has gone from a frequency of 122.300 MHz to the 8.33 kHz channel 122.305, similarly xzy.a25 to xyz.a30, xzy.a50 to xyz.a55, and xzy.a75 to xyz.a80 has not changed frequency at all. All of these 8.33 kHz channels are using exactly the same frequency as they did before, e.g., Blackbushe is still radiating and receiving on a frequency of 122.300 MHz. The channel offset of 0.005 does not change the frequency by an increment of 8.33 kHz, it merely instructs the transceiver to limits its transmit and receive bandwidths to an 8.33 kHz channel spacing based on the 25 kHz frequency.

To get a genuinely new frequency in 8.33 kHz land, you'd have to be using one of the new 0.010 or 0.015 channel offsets from a 25 kHz frequency designator, the new frequencies then being 8.33 kHz and 16.66 kHz offset from a 25 kHz frequency.

Iceman 8)

My brain hurts. :(
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By lobstaboy
#1657868
The only important bit is to make sure the numbers displayed on the radio are the same as what ATC give you.

But yes, it's silly - it's the only system I know of where the 'frequency' given to you and displayed on the radio is not the actual frequency of the radio signal. Bonkers or what?
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By GrahamB
#1657873
lobstaboy wrote:But yes, it's silly - it's the only system I know of where the 'frequency' given to you and displayed on the radio is not the actual frequency of the radio signal. Bonkers or what?

You’ve never tuned into a DME then?
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By lobstaboy
#1657902
GrahamB wrote:
lobstaboy wrote:But yes, it's silly - it's the only system I know of where the 'frequency' given to you and displayed on the radio is not the actual frequency of the radio signal. Bonkers or what?

You’ve never tuned into a DME then?


Certainly not!

But channel numbers don't count - they clearly aren't masquerading as frequencies in the same way.
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By vintage ATCO
#1657913
Iceman wrote:Any 8.33 kHz channel that has a channel offset of 0.005 from its previous 25 kHz frequency, e.g., Blackbushe has gone from a frequency of 122.300 MHz to the 8.33 kHz channel 122.305, [snip]


What you are describing is not 'channel offset' in the context of the way ATC uses it. As you state further in your post 122.305 is the same frequency as 122.300. It is just called 122.305 to indicate it is using 8.33kHz channel separation (not offset).

In ATC terms, channel offset means the same frequency being transmitted simultaneously from two different sites. Luton Approach is transmitted from both Luton Airport and Stansted, 129.545MHz from one, and 129.555MHz from the other. For a 25kHz radio this does not matter but it will not work with one set to 8.33kHz.

Disclaimer: I think this is still correct but I have been out of things for over 10 years.
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By rikur_
#1657916
lobstaboy wrote:
GrahamB wrote:
lobstaboy wrote:But yes, it's silly - it's the only system I know of where the 'frequency' given to you and displayed on the radio is not the actual frequency of the radio signal. Bonkers or what?

You’ve never tuned into a DME then?


Certainly not!

But channel numbers don't count - they clearly aren't masquerading as frequencies in the same way.

In my time at BA I recall the meetings of various very senior pilots agreeing upon the proposal to do it the way it is now done. They just wanted something that sounded/looked like a frequency, and didn't want to have to additionally select frequency and filter width .... nor have different ways of expressing a 'frequency' in different parts of the world (i.e. moving to a channel number system) ........ this alongside the debate as to whether GPS might be preferable to inertial reference for EGPWS.
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By Dusty_B
#1658233
EMA goes 8.33 on 3 January at 1500Z. No frequencies change - just jumping to channel numbers (ie, add 0.005).
(Exception is fire commander which remains 121.6)
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