Radios and electrical systems (VW)

Every 25 kHz frequency that converts to 8.33 kHz

But, why bother? Why not just use the intermediate ones (the 8.33 ones) for new applicants?

Interference?

If you transmit on a 8.33 frequency (say, 131.00833, aka ‘channel’ 131.010), it interferes with aircraft and ground based sets that are tuned to the nearest 25 kHz frequency (say, 131.000 with a 25 kHz bandwidth, aka ‘channel’ 131.000 – after all, that frequency should be tolerant up to 131.0125).

I recall a thread here some time ago where we discussed this.

Every 8.33k frequency has a 25k frequency right next to it. There should not be interference with existing 25k radios, otherwise any 8.33 usage would render existing 25k radios useless. And they would have to mandate immediate removal of all existing 25k radios and replacement of all of them with 8.33 ones which (you appear to imply) have better selectivity.

I think if you search on KX165A or something like that, you will find it.

As an example of my earlier post, why for example move London Info from 124.60 to the next one along, or Farnborough 125.25 to the next one along? It’s completely pointless.

Unless there is some covert plan to sell the 25k frequencies to Apple for airborne delivery of i-messages

I can’t see the need for the 8.33 thing when eurocontrol is introducing CPDLC into the upper airspace, this cuts down the voice traffic, the first attempt at this was very good news in terms of cutting down the voice communications but they had software issues.

According to Eurocontrol these issues have been fixed however yesterday I tried to log on to The CPDLC, it connected for a few seconds and then kicked me off so may be it has some way to go before becoming fully available.

The cynic in me sees 8.33 for low altitude ATC communications as a job creation for the eurocontrol boys that we have to pick up the tab for !

QuoteThere should not be interference with existing 25k radios, otherwise any 8.33 usage would render existing 25k radios useless. And they would have to mandate immediate removal of all existing 25k radios and replacement of all of them with 8.33 ones which (you appear to imply) have better selectivity.

That’s exactly what’s going on. Within the next two years or so all 25 kHz radios will obsolete and useless, and may no longer be used. In fact, if you get a new aircraft or new radio installation today, it is already mandatory to have 8.33 kHz capability.

8.33 kHz radios have selectable selectivity. If you tune to an “old” frequency, it enables 25 kHz selectivity, whereas if you tune to a “new” channel, it selects 8.33 kHz selectivity. This enables the use of both 25 kHz frequencies and 8.33 kHz channels simultaneously within the spectrum, as long as there’s no overlap. But a “new” 8.33 kHz channel can only be allocated and used once the nearby 25 kHz frequency has been converted to an 8.33 kHz channel too. Otherwise there would be overlap between the 25 kHz frequency and the 8.33 kHz channel. That’s why we’re now seeing the gradual conversion from 25 kHz to 8.33 kHz: To enable the nearby 8.33 khz channels.

QuoteLondon Info from 124.60 to the next one along

Actually that only seems to be the case. Because of the trick that I talked about to distinguish a 25 kHz frequency from an 8.33 kHz channel on the same frequency. So the move from 131.000 to 131.005 (in case of EHEH) is not really a change in center frequency, but only in bandwidth/selectivity.

Backpacker is right here. Most people don’t seem to realise that some channels are the same frequency, but called different (131.000 / 131.005) to indicate the selectivity used.
All new 8,33 kHz radio’s are actually 8,33 / 25 kHz radio’s. On 131.000 they will have a wider selectivity compared to the 131.005.

There a lot of countries which have to convert at least 25% of their frequencies to 8,33 kHz to meet the EU regulations