Primarily for general aviation discussion, but other aviation topics are also welcome.
#1571785
From CAP1606 these are the frequencies exempted.

Assignment(MHz) Primary Use Secondary Use Further information

118.675 Hang glider Para glider UK Mobile within UK FIR
122.475 Ballooning UK Mobile within UK FIR
122.950 Depcom Refer to UK AIP GEN 3.4
129.825 Micro light Site Specific for busy airfields
129.900 Gliding Parachute(AC) Hang Glider UK Mobile within UK FIR
Refer to BGA RP34 or BPA Radio Station Operators Guide
129.975 Gliding (CGFF) Site Specific for busy airfields
Refer to BGA RP34
130.100 Gliding UK Mobile within UK FIR
Refer to BGA RP34
130.125 Gliding UK Mobile within UK FIR
Refer to BGA RP34
CAP 1606 8.33 kHz voice channel spacing in the UK: Limited time exemptions
130.400 GlidingUK Mobile within UK FIR
Refer to BGA RP34
130.525 Parachute(DZ)UK Mobile within UK FIR
Refer to BPA Radio Station Operators Guide
135.475 Safetycom
Refer to UK AIP GEN 3.4, CAP 413 or AIC Yellow 014/2010
#1571997
I think it would it be fair to summarise that from Jan 1 2018:
No chance of 8.33 being delayed
Some frequencies will still be 25kHz and 8.33kHz accessible
25kHz radios will NOT be compliant
you may fly in a region where you can use a 25kHz radio without problems for you, but at some point, it will interfere with compliant communication
ALL your radios should be 8.33 capable
NORDO has always been an option, if you conform to the restrictions on where you fly

I'm not an expert on this but in the end, if you want to fly using a radio, it has to be compliant with the requirements doesn't it? You COULD use it as a prompt to update your whole audio panel and improve the aircraft (other aircraft may have different issues)...
#1572029
Most of that summary sounds correct, but:

neilmurg wrote: you may fly in a region where you can use a 25kHz radio without problems for you, but at some point, it will interfere with compliant communication
ALL your radios should be 8.33 capable


No, it is highly unlikely any halfway decent 25kHz set will ever interfere with compliant communication, and anyone monitoring your transmission with a spectrum analyser would be hard pressed to tell what you were using to transmit, according to some well qualified commentators in previous threads on here.

And even if you disagreed with that assertion there is no reason not to keep a 25kHz set for 121.5, 135.475, etc.
#1572078
riverrock wrote:Because if you had 2 radios, you can save £1000 by not changing the 2nd one.
OK, but you're saying, 'If you have 2 radio's you can change to having 1 and a bit radios'. It is of course entirely your choice.
User avatar
By T67M
FLYER Club Member  FLYER Club Member
#1572429
All this talk of "what happens when a 25kHz radio transmits" got me thinking of a simple experiment. I have an aircraft with 8.33kHz radios, so how about tuning to an unused "shoulder" channel adjacent to an active frequency and seeing what happens?

I chose Gatwick Director on 126.825MHz as it's a fairly busy frequency (!!!) and I should get lots of transmissions from different aircraft without having to sit around in the cold for too long. So I set my Trig TY96 to 8.33kHz channel 126.835, on the nominal frequency of 126.8333MHz. As predicted, I couldn't hear a single aircraft - presumable all the airliners have 8.33kHz radios fitted, and there were no GA aircraft on frequency at the time. What was surprising, however, was that I could clearly hear every transmission by Gatwick Director! Whilst they're still using a 25kHz channel, there is no compulsion for them to have 8.33kHz radios, but as has been said in these fora many times, "it is highly unlikely any halfway decent 25kHz set will ever interfere with compliant [8.33kHz] communication".

So - is Gatwick Director using a grotty old radio set? Is the theory wrong? Or is Gatwick Director actually a CLIMAX channel using offset carriers, in which case why isn't it listed in CAP1533 or CAP1606?
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User avatar
By Marvin
#1572462
T67M wrote:All this talk of "what happens when a 25kHz radio transmits" got me thinking of a simple experiment. I have an aircraft with 8.33kHz radios, so how about tuning to an unused "shoulder" channel adjacent to an active frequency and seeing what happens?

So - is Gatwick Director using a grotty old radio set? Is the theory wrong? Or is Gatwick Director actually a CLIMAX channel using offset carriers, in which case why isn't it listed in CAP1533 or CAP1606?


CLIMAX frequency. It’s done for area coverage and also to some extent redundancy.

The Tx are maintained to a high standard on a regular basis and all parameters checked. Very little to adjust on modern TX as they are all firmware controlled and rarely drift. Manufactures frequently quote 5 to 10 year maint cycles although they are checked much more frequently.

I think the CAP just states CLIMAX frequencies as a blanket statement with out listing the specific ones. Don’t think it lists the London Info freqncies for the same reason.
#1573144
This statement from the CAA on Pilotweb has massive implications.
‘1. If an aircraft is only communicating to ground services on 25 kHz frequencies, then it is permitted that they continue to use a 25 kHz radio until the end of 2018. However, if their flight means that they communicate to any ground service that has transitioned to an 8.33 kHz channel, then they must also be using an 8.33 kHz capable radio. This applies to all aircraft and also overrides part 2 of this list below.

From the CAA GA web pages I've found this.
Ground station conversions

Ground stations will begin to convert to 8.33 kHz VCS during 2018. The conversion date will depend on the decision taken by each individual ground station. Airspace users are strongly advised to ensure they use up to date and accurate information before flying and follow any instructions given by units.

When your flight needs you to only communicate on 25 kHz frequencies, you will be able to continue to use your 25 kHz radio for a limited time period of 12 months (to 31 December 2018). However, when any ground station or service throughout your flight converts to an 8.33 kHz channel, you must only communicate on an 8.33 kHz capable radio.

There's no date on the CAA pages showing revisions so I don't know when this changed nor is there an alert on Skywise.

Having been trumpeting the party line about the need for change, trying to convince a/c owners, operators and pilots to buy new radio equip this well and truly pulls the carpet from under my feet. :oops:
User avatar
By Rob P
#1573147
I am hopeful that through next year there will be a sticky somewhere on this forum that informs us which stations have gone to 8.33. My bet is that Tim will come up with a helpful mod on SkyDemon*

Supplementary. If Stansted (for example) goes 8.33 are we allowed/forbidden to listen/squawk on 25?

Rob P

*other navigation software is available