UdoR wrote:
Do I understand it right that any submission (TRANSMIT) from a radio is technically the same be it a 25 kHz radio sending on 125.025 or be it an 8.33 kHz radio sending on 125.030?
125.030 is not a frequency, it’s a channel name. The frequency the radio is sending on is actually 125.025 MHz, same as for a 25 kHz-spaced one.
The channel named 125.035 has an actual carrier frequency of 125.03333 MHz, and 125.040 has 125.04167 MHz. I know, it’s confusing.
The exemption for 8.33 for VFR in certain chunks of airspace is running out here in Denmark. From 1/1/2023 8.33 is finally required everywhere. I believe EASA wrote a letter (back in ?2017, I’ll find it in a minute) stating that any extra com sets beyond what is required (usually only one, for NCO ops) can still be an old 25 kHz set. In other words, airplanes with one 8.33 and one 25 kHz set (not at all uncommon) do not have to disable the 25 kHz set. They can still use it for e.g. monitoring (ATIS reception), for 121,5 emg use or for other use authorized by ATS. Whether this is (still) true or not is of some significance since there are voices telling aircraft owners they have to get rid of any 25 kHz sets to maintain airworthiness. Some of you will know the definite answer to that I guess.
French GEN1.5 has IFR requirement for carriage of 8.33khz (except for sate aircraft) and VFR in most cases airspace/aerodrome where radio is mandatory…if radio is not mandatory for VFR in some airspace/aerdrome, why you need it to be 8.33khz? at some point one has to use their brains
Having 25khz in the pannel is not an issue
8_33isg_08_ip04_actionisg4_15_d53915_letter833vcsbelowfl195_easa_pdf
I am not aware of the legality of using 25kh to listen of transmit in 8.33kz frequency/spacing (some ATC have dedicated 25khz frequency/spacing, this is the case for 121.5 which is available in both 8.33 and 25)
Night NVFR require 8.33khz, more interesting at night when 25khz keeps working for talk & listen on COM2 but does not work for runway PCL
huv wrote:
Whether this is (still) true or not is of some significance since there are voices telling aircraft owners they have to get rid of any 25 kHz sets to maintain airworthiness. Some of you will know the definite answer to that I guess.
There has been no change in legislation. Carriage and use of 25 kHz radios is perfectly legal – but of course only for 25 kHz channels. It is not (and has never been) legal to “cheat” and use them for 8.33 kHz channels with the same frequency. But of course when it comes to listening to an 8.33 kHz channel like an ATIS no one would ever notice.
It is not permitted to install a 25 kHz radio, but that’s also not new – it’s been like that since the 8.33 kHz requirement was introduced.
Ibra wrote:
Night NVFR require 8.33khz, more interesting at night when 25khz keeps working for talk & listen on COM2 but does not work for runway PCL
What the regs say is that you must have 8.33 kHz capability when you operate in airspace where radio carriage is required. (Regardless of whether that airspace actually uses 8.33 kHz channels.) There is no general requirement to have a radio when operating night VFR in classes E-G.
Quoting @udoR
Before I try it out myself I don’t want to disturb no one. Do I understand it right that any submission (TRANSMIT) from a radio is technically the same be it a 25 kHz radio sending on 125.025 or be it an 8.33 kHz radio sending on 125.030?
Not sure I understand what you mean.
Source wrote
If you accidentally select 132.005 when you should have selected 132.0 you will be on the right frequency but with a narrower bandwidth, but the chances are that you will be able to communicate. But if you select 132.0 when you should be on 132.005 your radio will be in 25kHz mode and you are likely to cause interference on several 8.33 channels and you may hear transmissions from adjacent frequencies.
The above LAA quote is wrong.
See e.g. here
It is BS. The LAA should know better, but it isn’t surprising… one probably needs to be into electronics to get this easily.
The transmission bandwidth is simply the audio bandwidth. That is a property of AM (amplitude modulation). So any radio, whether 25k or 8.33k, set to 132.000, will transmit the same signal. Read the above link – the proof is there.
All that setting 132.000 versus setting 132.005 on the radio does is to change the receiver selectivity. And in both cases it is centred around 132.000.
The 5kHz add-ons change basically nothing and you can use a 25k radio. The vast majority of “GA usage” ground stations were “converted to 8.33” in this way. It enables 25k radios to be used on 8.33 channels. “Real” 8.33 comms is done on the two intermediate channels which are the 25k multiple plus 8.333333 and 16.666666 and these are published with different numbers, not .005. For example 132.010 would be a “real” 8.33 channel (actually 132.008333333 but they don’t use that because it would complicate both radio user interfaces and peoples’ brains).
All this has been written up in detail in this thread and the above linked one.
the chances are that you will be able to communicate
It is 100% certain you will be able to communicate, when setting a 25k radio to 132.000, talking to a 132.005 unit 
Snoopy wrote:
But if you select 132.0 when you should be on 132.005 your radio will be in 25kHz mode and you are likely to cause interference on several 8.33 channels and you may hear transmissions from adjacent frequencies.
Well, in the exact scenario written there (selecting a 25kHz channel on a 8.33kHz-able radio), in my understanding, no for the transmitting side, and true for the receiving side.
With a very old radio, with very old components (maybe vacuum-tubes era? I’m not sure.) that are not very frequency-precise, when set to 132.00, the radio might actually be emitting at 132.10kHz, or at 132.07kHz, or at 131.98kHz, or at 131.92kHz; I expect these are all within the (old) spec. So in that case, in a 8.33kHz environment, you might indeed transmit on another channel than 132.005.
But in any not truly ancient radio, the frequency precision will be far better than allowed by the (old) spec, and you’ll be transmitting at a frequency very close to 132.00, well within the tolerances of the new 8.33kHz spec, so you will transmit only on the 132.05 channel, not any other.
OTOH, I remember flying through Karlovy Vary TMA shortly after the switch to 8.33kHz spacing, with a G1000 plane, 8.33kHz able, but set to 25kHz spacing (some **** had changed the setting on that club/rental plane…). Quality of communication was bad, but I could communicate with them. It is only at destination that I cottoned on why I couldn’t set the frequencies I was given, I put the plane in a holding pattern on autopilot, and fiddled in the aux page until I found the setting.
If you don’t need to use actual 8.33 channels often, keeping the radio on 25kHz steps saves a lot of knob twisting… I keep the GNS430W on 25kHz most of the time.
