wait another 5 years, then revisit this issue. 8.33kHz frequencies will remain exotic for a long time to come.
I suspect you’re right. Let’s hope so!
So, was that earlier 8.33 thread complete rubbish?
Is it really true that 8.33k channels will render the 25k channels unusable?
I don’t think so!
Maybe some very old radios will be affected but anything made in the 1990s or later (basically a KX155 onwards) should have enough selectivity.
And, unless I am missing something massive, every 25k channel pair will have two 8.33k channels between them. So all the 25k channels stay as they are. Tuning say 125.25 on a 25k radio will tune the same centre frequency as tuning 125.25 on an 8.33k radio.
So, was that earlier 8.33 thread complete rubbish?
No why?
Is it really true that 8.33k channels will render the 25k channels unusable?
No, the other way around could be…
And, unless I am missing something massive, every 25k channel pair will have two 8.33k channels between them. So all the 25k channels stay as they are.
Correct
Tuning say 125.25 on a 25k radio will tune the same centre frequency as tuning 125.25 on an 8.33k radio.
125.25 or 125.250 is a “25 kHz frequency” a 8.33 kHz transceiver tuned to this frequency will use 25 kHz specs (selectivity / bandwidth). When an 8,33 kHz radio is tuned to 125.255 it is actually tuned to 125.250 as well, but now uses 8.33 kHz specs (selectivity / bandwidth). 125.25*5* is to indicate that is an 8,33 kHz “frequency” and your transceiver should use filters for that.
The problem with the whole 8.33 kHz transition is that everything will continue to seem to work if you don’t switch switch to an 8.33 kHz radio. In other words, if you use a 25 kHz radio to communicate on an 8.33 kHz channel with a center frequency that falls on a 25 kHz boundary, things will simply work and nobody is going to notice you don’t have an 8.33 kHz radio. (For example, if ATC uses the new 8.33 kHz “channel” 131.005 and an aircraft transmits on the old 131.0 frequency, they are going to be perfectly fine communicating with each other.)
The problem will only arise once the nearby 8.33 kHz frequencies are actually allocated within the same area. Your 25 kHz selectivity may cause interference on that nearby frequency (but you won’t know that) and you may be picking up their transmissions since they transmit on a frequency that falls within your selectivity.
And obviously the second problem will eventually come if you need to tune to an 8.33 kHz frequency, but you can’t input that on the dial because your radio doesn’t do 8.33 kHz. But my gut feeling is that the frequencies that are required for low-level VFR flight will remain on the same frequency for the foreseeable future – they just switch from 25 kHz to 8.33 kHz selectivity.
That’s why the implementation plan is so drawn out. At this moment, any aircraft flying IFR or in class A/B/C airspace, or any new aircraft, or any aircraft getting an avionics upgrade, need to have/get 8.33 kHz radios. Also, no equipment may be sold anymore that doesn’t have 8.33 kHz selectivity. In a few years time, 8.33 kHz capability will be mandatory for all aircraft. For CofA aircraft, my gut feeling is that from that moment onwards a CofA cannot be extended anymore if you don’t have an 8.33 kHz radio.
But that leaves a whole slew of PTF aircraft/microlights and similar untouched. They’re not on a formal maintenance regime that will notice a non-compliance with the 8.33 kHz rules so their owners will not be triggered/forced to upgrade. Combine that with owners that do not follow the regulatory changes all that close, have no subscription to magazines, don’t read internet forums and such, and the result may be lots of interference on 8.33 kHz frequencies.
8.33kHz frequencies will remain exotic for a long time to come.
I beg to differ. Within the EU, ALL frequencies, except 121.5 and a very small number of other frequencies, will be converted to 8.33 channels in the near future. The EU mandated deadline is either the start or the end of 2018 – I can’t look that up just now.
Most of these conversions will be an administrative change, where the center frequency stays the same but the selectivity is switched from 25 kHz to 8.33 kHz. Like EHEH which changed from 131.0 (center frequency 131.000 with 25 kHz selectivity) to ‘channel’ 131.005 (center frequency 131.000 with 8.33 kHz selectivity) on Jan 8th of this year. But my gut feeling is that somewhere during 2018 we will see the appearance of “proper” 8.33 kHz frequencies. Probably initially for frequencies with a select user base, like company frequencies. But later on mainstream frequencies as well – particularly if Ofcom and similar organizations decide to charge less for a “proper” 8.33 kHz than for an 8.33 kHz frequency that coincides with an old 25 kHz frequency.
wait another 5 years, then revisit this issue. I bet nothing much will have changed. 8.33kHz frequencies will remain exotic for a long time to come.
My understanding is that The Netherlands has mandated 2017 as the latest switch over for airfield frequencies – Eindhoven TWR is the leader and is already an 8.33kHz frequency
Your 25 kHz selectivity may cause interference on that nearby frequency (but you won’t know that) and you may be picking up their transmissions since they transmit on a frequency that falls within your selectivity.
Huh? how is receiver selectivity issues going to cause transmitter interference? I’d be very surprised if transmitter spectrum is any different in 8.33kHz mode versus 25kHz mode.
Ok, 25kHz only transceivers might get away with a larger center frequency tolerance, but I doubt this is going to be a big problem, given that the cockpit is a relatively climate controlled environment (at least after a couple of minutes), given that pilots don’t like to freeze or sweat 
In other words, if you use a 25 kHz radio to communicate on an 8.33 kHz channel with a center frequency that falls on a 25 kHz boundary, things will simply work and nobody is going to notice you don’t have an 8.33 kHz radio.
That’s true, if the frequency tolerance on your 25 kHz transmitter is tight enough, but is it? If you can be certain that it is, why would 8.33 kHz radios switch to lower selectivity if you tune a 25 kHz channel?
Agree.
If you have anything resembling a modern radio (built with solid state electronics, and not with vacuum tubes) your transmissions will be exactly on the nominal frequency. So for transmit it will not matter whether you select the old 131.0 frequency or the new 131.005 channel – the center frequency will be exactly on 131.000.
But for backwards compatibility reasons your 25 kHz receiver needs to receive anything that falls within a 25 kHz spectrum around the center frequency. Which includes the two closest 8.33 kHz frequencies. With a proper 8.33 kHz receiver you can filter those out, which means less interference.
And that’s what I meant. If you know what you’re doing (or are conveniently ignorant) you can select the 131.0 frequency (which is now the 131.000 ‘channel’ – with 25 kHz selectivity) and communicate with anyone on the 131.005 ‘channel’ with no difficulty. It will only start causing problems once the 130.990 and 131.010 channels (with nominal frequencies 130.99167 and 131.00833 respectively) are being used in the same area, as they do interfere with 131.000/25 kHz but do not interfere with 131.000/8.33 kHz.
I have no idea how many GA aircraft are flying with modern, solid state electronic radios, and what percentage uses older, or even vintage technology. And I have no idea about the exact frequency tolerance on transmit, for solid state, transistors and vacuum tubes. Peter, do you know? How easy/hard is it to implement 8.33 kHz selectivity vs. 25 kHz, both on transmit and receive, on those kinds of devices?
(Of course what makes things complex is that a modern 8.33 kHz radio doesn’t simply mean upgraded filters. It needs at least three sets of filters: A 100 kHz filter in case 121.5 is selected, a 25 kHz filter for the old-style 25 kHz frequencies, and an 8.33 kHz filter for the new 8.33 kHz channels. In reality that means a radio replacement rather than a radio filter upgrade.)
A recent Europe Air Sports newsletter says that from 1/1/15 all aircraft flying in the Netherlands must have 8.33 kHz radios, including VFR, no mention of exemptions at lower levels.
I was thinking of passing through Dutch airspace shortly. As I have been holding off re-equipping pending better kit becoming available, I wonder whether I would have a practical problem in low-level VFR. Folks here doubtless have the up to date position?
