Primarily for general aviation discussion, but other aviation topics are also welcome.
  • 1
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
#1573978
The discounting period started several years ago and has now finished, so, depending on DOC - effectively the volume of space the service covers - 25kHz stations are paying between £2000 and £9000 PA already. 8.33kHz channels are one third of the price for the same DOC. This is nothing to do with the CAA, it is an OfCom thing, supposedly to encourage users to be more efficient in their spectrum use so that spectrum can be freed up for other users. The fact that this is not possible in the international air band didn't seem to bother them - they went ahead anyway.

It is wrong to conflate licensing costs with the arrival of 8.33kHz. Licensing is an OfCom thing and they, uniquely in the entire world, have decided to impose these high charges on the aviation spectrum. Europe has decided, again uniquely in the entire world, to go for 8.33kHz. The two things are completely unrelated but happen to have come together at more or less the same time to create the perfect storm for us here in the UK.
johnm liked this
User avatar
By Paul_Sengupta
FLYER Club Member  FLYER Club Member
#1574021
The Westmorland Flyer wrote:The two things are completely unrelated


Maybe, but I was told (I won't say who by) that the tripling of charges for 25kHz frequencies was done deliberately to "encourage" the uptake of 8.33. I know not much in government is joined up, but it seems plausible.
#1574033
Yes. I'm aware of several airfields that have significantly reduced their license costs by reducing DOC. This applies especially to air/ground stations, which can go for as little as 10nm/2000ft. Not an option for airfields with any sort of approach procedure.

Of course radio waves, aka little wiggles know nothing about such niceties as DOC and carry on regardless, making something of a mockery of the whole thing.
#1574034
Paul_Sengupta wrote:...I was told (I won't say who by) that the tripling of charges for 25kHz frequencies was done deliberately to "encourage" the uptake of 8.33. I know not much in government is joined up, but it seems plausible.

I'm not sure that there was any collusion but there is no doubt whatsoever that spectrum pricing came along at a very convenient time for the CAA vis a vis 8.33kHz. It is interesting to note that initially the CAA was vociferously against spectrum pricing for the air band but soon acquiesced. Quite why, I couldn't possibly say...
User avatar
By flybymike
FLYER Club Member  FLYER Club Member
#1574036
The Westmorland Flyer wrote:Yes. I'm aware of several airfields that have significantly reduced their license costs by reducing DOC. This applies especially to air/ground stations, which can go for as little as 10nm/2000ft. Not an option for airfields with any sort of approach procedure.

Of course radio waves, aka little wiggles know nothing about such niceties as DOC and carry on regardless, making something of a mockery of the whole thing.


Isn’t the distance the little wiggles will travel determined at least in part by the output power of the transmitter?
#1574071
flybymike wrote:Isn’t the distance the little wiggles will travel determined at least in part by the output power of the transmitter?

Yes, very much so in fact. But there are other equally important parameters, notably terrain, antenna gain and feeder loss at both ends of the link, etc. This all makes DOC something of an imprecise art form, especially in hilly terrain like we have up here in tWF-land.
By GlynneRees
#1574888
The Westmorland Flyer wrote:Sorry I'm a bit late to this - been away.
GlynneRees wrote:I need to check if my understanding is right here...

Broadly correct. There is considerable confusion with 8.33kHz because, as you rightly say, the channel "frequency" is not the same as the actual frequency. Most people, when confronted with, say, 123.205 will think "Ahha! That's a frequency." It certainly looks like a frequency but it is really a channel description that is an approximation of the actual frequency. A massive opportunity to move to the use of proper channel nomenclature, e.g. "change to channel 41" was missed, despite this being a commonplace solution for virtually all other radio users.
...When I called for radio check I got a 4, with comment that we are a bit distorted.
So what could be actually going on?

Difficult to say. It could be that your transmitter is well off frequency but if it's a modern (say last 25 years) radio that is exceedingly unlikely. More likely is the reduction in audio bandwidth that 8.33kHz imposes. This will tend to make 8.33kHz channel audio sound muffled, with fewer higher frequency components. There is a common misconception that 8.33kHz will make radio communications quality better. It most certainly will not: at best people will notice no change, otherwise it can only make the audio sound worse.


Thanks for the helpful reply. We just got our aircraft back with new Garmin 833 radios (255A and GTN650), our 23+ yr old Narcos retired. We are getting 5's every time set 123.2 (25kHz spacing). Not planning to switch to 833 channel selection on the new radios until there are stations we need to talk to. It looks like 833 mode actually lets you select both 25khz and 8.33 KHz spacing so there are many many more clicks to get where you want to be. I still believe the OS Notam is worded incorrectly. That is something we can do without as everyone tries to get their head around the change over.
By riverrock
FLYER Club Member  FLYER Club Member
#1574969
GlynneRees wrote:It looks like 833 mode actually lets you select both 25khz and 8.33 KHz spacing so there are many many more clicks to get where you want to be.

This is something that should have been better communicated from the start - as many people don't seem to "get it". This confusion has come round time and time and time and time again on here and in person (the one exception is one ICOM model which needs a firmware update to do this).
By GAFlyer4Fun
#1574973
Reading the manual of all radios under consideration before making a purchasing decision would avoid a lot of confusion and also reveal which radios are more practical/user-friendly than others at that price point.
By PaulB
#1575126
Sorry, but this may be a silly Q, but everyone seems to think that 8.33 is a bad idea, but I guess that it's been internationally decided and that all countries are switching?

We surely couldn't have a situation where United 123 (for example) was given a frequency that it couldn't speak to in its 25kHz COM box?

Second silly question.... 8.33 doesn't really divide into 100 or 1000 very easily so we have a silly situation where some frequencies "electronically" won't be changing, but we'll call them something different. Why was 10kHz spacing not a better idea.... 10 divides into 100 and 1000 really easily?
User avatar
By Marvin
#1575128
It’s changing at a European level not Internationally. So USA, Australia etc continue on 25khz spacing.

As for 8.33 as opposed to 10.0 KHz. The 8.33 is about the minimum spacing to provide a guard band between the 6khz bandwidth use by the modulation by 3Khz of the voice. If your going to do it then go for max capacity in one step.
By PaulB
#1575361
So is it conceivable that a US or Australian aircraft could come to EASA land and be asked to contact a frequency that their avionics can't do, or are they all 8.33 anyway?

Second silly question......

If a ground station has a frequency of (say) 118.025 and it changes to 8.33, this will be displayed and spoken as 118.030 (according to this http://publicapps.caa.co.uk/docs/33/CAP ... tation.pdf) but will remain operating on 118.025.

How will the radio in the aircraft know to display the new "frequency" (which I believe is called a channel, but we won't be using that word)

We have a 430 but it's so long since I've even seen the aeroplane, never mind flown it that I've forgotten what it displays!
By johnm
FLYER Club Member  FLYER Club Member
#1575363
We have a 430 but it's so long since I've even seen the aeroplane, never mind flown it that I've forgotten what it displays!


I hope that you get to see it soon :-)

The 430, when configured for 8.33 in the settings will display the frequency that you are required to dial in. The firmware sorts out the fiddly bits.
User avatar
By Rob P
#1575368
GAFlyer4Fun wrote:Reading the manual of all radios under consideration before making a purchasing decision would avoid a lot of confusion and also reveal which radios are more practical/user-friendly than others at that price point.


Other suggestions for really gripping ways to spend your leisure hours will be welcomed.

Rob P
  • 1
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11