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Why 8.33 KHz[edit]

How was the figure of 8.33 KHz for the new channel spacing arrived at ? Why wasnt a round number like 5, 6, 9, 10, or 12.5 KHz used ?

A good question! In Europe they decided to take the 25 kHz channel spacing and cut it into thirds, rather than halves to make optimal use of the band. In North America the plan was to go to digital radio with 4 or 8 channels sharing each frequency instead. Of course since airplanes fly all over the world this really makes it difficult since the same system needs to be used everywhere or else aircraft need two different radios to fly in the North America and Europe. The US digital plan seems to be on hold lately. It is likely that the airband frequency congestion will solve itself due to the current shrinkage in air traffic anyway. This probably all needs to be included in the article, I will see if I can find a reference for it all. - Ahunt (talk) 15:35, 30 November 2008 (UTC)
I am not a radio engineer but ;) I think it's because 4kHz is an acceptable bandwidth for a human voice (we can hear frequencies ~20Hz -> 20kHz but most information in the voice is in the lower 4kHz) and in AM transmission this 4kHz is mirrored around the carrier frequency giving 8kHz bandwidth (see Baseband#Modulation). If you divide the existing channels by a whole number the existing 25kHz channels won't change and can be used by existing radios (i.e. no expensive, mandatory replacement). Dividing by 3 gives the most additional channels with 8kHz bandwidth for voice plus a bit left over for a Guard band. Of your proposed divisions, only 5 and 12.5kHz would leave the existing channels intact and 5kHz is enough bandwidth for voice only if you use SSB. Dividing by 12.5 would work but isn't the most efficient - you can get a third one in.
AM is used (presumably) because it's simpler and therefore safer. If Airband switched to SSB you could go to 4.166kHz spacing and have 6 times as many channels as now but at a cost of more expensive equipment and less reliability and again you'd need to replace ALL radios at the same time. (and is 0.166kHz enough for a guard band?)
I don't know why 25kHz spacing was chosen in the first place but I'd guess it's so there are large guard bands to reduce the chance of interference and improve safety.
My 2c worth of wild guesses :) Johnnie Rico (talk) 04:06, 5 February 2009 (UTC)

Does anyone know if the 8.33 kHz channels are listed anywhere? I have looked, but all the on-line lists seem to have only the old 25 kHz channels. —Preceding unsigned comment added by (talk) 13:15, 1 July 2010 (UTC)

Adding references instead of tags[edit]

If one has a reference for a fact in one's back pocket, one would be better advised to add the citation to the article, rather than tag it with "citation needed" in the hopes that someone else will find the citation one is sitting on. --Wtshymanski (talk) 14:50, 14 February 2011 (UTC)

...and if one doesn't, one should refrain from adding unsourced content to Wikipedia. (talk) 05:05, 19 February 2011 (UTC)

citation nazi warning[edit]

Look, here's the deal: this website may be a reliable source for the radio frequencies used by some airports in the UK, but it certainly doesn't back up the sweeping generalizations that have been attributed to it recently. I'm assuming that someone confused the nicknames of the sources or something, so I've gone ahead and replaced most citations to that article with {{fact}} tags in the hope that those people actively seeking out sources will correct their mistakes swiftly.

That said, I feel compelled to warn those involved with editing this article that an editor less inclined to assume good faith might very well think that these incorrect attributions were intentionally misleading, which is a severe violation of Wikipolicy. So for the good of everyone involved in the editing of this article, and of Wikipedia as a whole, I intend to make regular practice of removing new assertions that are unsourced or incorrectly sourced, and bringing the behavior of any editor who persists in adding unsourced/poorly sourced content to this article up for review.

IOW, please edit mindfully. (talk) 05:25, 19 February 2011 (UTC)

Thank you for your comtributions to Wikipedia and your good faith edits to this article. It would appear that I attributed the name "freq" to the wrong reference (U.K. frequencies). I have now removed this confusing reference, and the correct reference has now been used instead. I hope this clears up the mistake and and helps those editors that previously caused the article to need a reference at the end of every line. Had the article not been sprinkled with [citation needed] in the first place there would have been no need to have inserted so may reference points. Francis E Williams (talk) 11:18, 19 February 2011 (UTC)
I have to agree with User talk: that some refs being added here are not properly sourced or are sourced to refs that do not support the text, he or she fixed some of that, but it has largely been reverted. The article is also now badly organized, choppy and in need of a re-write. I have just been waiting for User:Francis E Williams to get done with it so I can do a complete ref check and copy edit. So please do leave a note here when you are done. - Ahunt (talk) 13:11, 19 February 2011 (UTC)
Thank you for your patience, but I have no futher edits to add to this article. I note the above comments regarding the "choppy" nature of the layout, I would suggest using sub-sections rather than page breaks for different topics. Every time a new subsection was added, it was reverted by the above editor to a page break. Pehaps he or she could decide on a better approach to layout that would still allow the reader to choose points of interest. As this is a world wide subject according to the lead section, there should be no reason to countrify it at all. Unfortunatly many American references that could have been used are attached to pages containing adverts and as such do not comply with WP:RS. Perhaps a list of the references required could be made, or at least those that are there be read in full to see if they actually do support the section to which they apply. It is good to see such determination to strip out much of what was originally added by various contributors to articles. Perhaps if this procedure could be adopted to all Wikipedia articles we would have so much less to edit and less references to find for every sentence added. Francis E Williams (talk) 13:45, 19 February 2011 (UTC)
No one has suggested making the information country specific. The layout and section levels are set out in WP:MOS and my section level adjustments were in accordance with the MOS. In a preliminary check of the references there is a much bigger problem as User talk: outlined above, even since his or her fixes you have peppered the article with refs that don't support the text. Fortunatley we have some refs available already in the text, it is just a matter of putting them back in place and adjusting the text to conform to the refs, which I will do. - Ahunt (talk) 15:10, 19 February 2011 (UTC)
Are you now saying you didn`t pepper the article with [citation needed] every time text was added in the past? I have to leave you to it as my time here is limited. Francis E Williams (talk) 16:07, 19 February 2011 (UTC)
I have only added tags where uncited text was added. Regardless I have checked all the refs, removed the ones that do not support the text, added refs, re-organized the text, added text and refs, fixed the headings and heading levels. The article is now generally cited and there are no outstanding tags at this point in time. - Ahunt (talk) 17:01, 19 February 2011 (UTC)

──────────────────────────────────────────────────────────────────────────────────────────────────── I note there are now only 13 refs, all original and placed more sensibly at the end of the paragraphs. A much better solution than previously. The text sections look good, as it is basically as it was before your last copyedit. I take it you are now pleased with the end result. The sourced refs and content I included weren`t wasted after all. We seem to have improved the article between us, don`t you think? Francis E Williams (talk) 18:52, 19 February 2011 (UTC)

I have supplied the needed reference for the statement thatonly 121.5 retains 100 kHz channel spacing, added some clarification about licensing and deleted the [citation needed] regarding heterodynes. The supplied references to capture effect and heterodyne explain the principle without the need of further references. Altaphon (talk) 07:41, 1 November 2013 (UTC)

Thanks for adding those citations, that helps immensely. I have restored the tag you deleted. That para contains technical claims that must be either cited or removed as per WP:V. If you can supply refs then please do add them otherwise this para should be removed. - Ahunt (talk) 11:44, 1 November 2013 (UTC)

Channel numbers[edit]

We have lost the fact that there were changes in the allocation to voice channels. In 1992 760 were proposed. 720 are actually assigned from 118.00 up to 135.95Mhz. The extra 40 extend to 136.995 Mhz, some for future use. Two seperate refs were found to support this change in the voice band plan. Should the sitaution be clarified to the reader to maintain accuracy of the article, and could this fact be the cause of the apparently conflicting references?.Francis E Williams (talk) 19:12, 19 February 2011 (UTC)

According to the ref you added from 1992 the extra 40 channels between 136 and 137 mHz were added on 01 Jan 90 and are in use by ATC for air traffic use. This is backed up by the current TC ref. I couldn't find the ref that said that these were being held for future use, and I had two refs that said they are in current use, so I deleted that text. Which other ref contradicts these? - Ahunt (talk) 19:30, 19 February 2011 (UTC)
O.K., I can see the problem, this ref [1] "freq" has both data in it. **The air canada ref just covers the whole band in one go** . If you look at the top of the VHF band you'll see the 720 channels between 118 -135.95. Look under this section to "other frequencies", you`ll see the other 40 channels 136 - 136.975. I just include this data because the article says Airband is 118 -137mhz at the outset. I didn't say that any ref does contradict, just that the text had two sentences, one referring to the "overall 760 ch. allocation", and another mentioning "720 ch. between 118 - 135.975". If we just change the statement "As of 2011 there were 760 channels available for amplitude modulation voice transmissions, in the 118 - 136 Mhz section of the band." to - 137 mhz, and include the future use eentence about the 40 other channels that should do it, what do you think? Francis E Williams (talk) 19:46, 19 February 2011 (UTC)
Ah, I see the error, that was my mistake. I have fixed that. My understanding from the FAA and TC refs is that the 40 channels above 136 mHz have been in use since 1990 and remain so today, even though this other ref says "Air Control/Unicom/Future Use" I see no indication that is correct. In fact this 1993 Industry Canada agreement allocates most of these freqs to ATC back then. - Ahunt (talk) 20:13, 19 February 2011 (UTC)


Any reason why we dont have a reference to the UHF airband as used by military aircraft? MilborneOne (talk) 20:12, 19 February 2011 (UTC)

Just lack of refs. I may have one on paper, let me check. - Ahunt (talk) 20:14, 19 February 2011 (UTC)
Found, added. - Ahunt (talk) 20:24, 19 February 2011 (UTC)
Thanks. MilborneOne (talk) 20:28, 19 February 2011 (UTC)
(Edit conflicts):::I would tend to agree, but might I suggest the retitle / move page to "Aircraft bands", then the article could include all H.F., V.H.F., and U.H.F. etc. At present we are saying it is a VHF band 108 - 137 mhz. What do you think, most of the refs are here already for the general lower frequencies.HF. - VHF,VHF. - UHF.,-UHF - 1.2ghz I took out the Military bit in the lead because it was all about the civil avaiation frequencies. What do others think?.Francis E Williams (talk) 20:41, 19 February 2011 (UTC)

CLIMAX multi-carrier system[edit]

The CLIMAX multi (i.e. offset) carrier system is referred to in the article as if it is a new happening ('under discussion'). I am not sure where the author is located but, as an ex-telecomms apprentice with the old National Air Traffic Control Services (UK), I recall that this system (to achieve greater geographical coverage but using apparently just one VHF/UHF frequency) was in use within the UK at least during the early 1970s. Indeed, the situation has come around full circle as there are now moves to possibly revert to just one ground transmitter on a frequency (Single Carrier Mode - see to get around technical and other problems associated with carrier-offset systems such as CLIMAX. Not really related to CLIMAX, it might be worth mentioning the use of this frequency band allocation for ACARS and the like. Mentioning ATIS is valid but one should not forget VOLMET. Longfinal (talk) 18:40, 9 September 2012 (UTC)


OFCOM link which is used as a citation for 'listening to airband in UK is illegal, without a license' doesn't appear to say this explcitly: it says: "Although it is not illegal to sell, buy or own a scanning or other receiver in the UK, it must only be used to listen to transmissions meant for GENERAL RECEPTION. The services that you can listen to include Amateur and Citizens’ Band transmissions, licensed broadcast radio and weather and navigation broadcasts."

I don't know : but wouldn't 'navigation' and 'GENERAL RECEPTION' criteria apply to airband ? (is is secret/private information, or general navigational information?) — Preceding unsigned comment added by (talk)

General reception is really stuff that is broadcast for the general public to hear, like listening to the BBC radio or amateur operators, discussion between aircraft is a private conversation and not sent with the intent for others to listen so it is illegal. MilborneOne (talk) 12:44, 3 December 2014 (UTC)