Acronym not found ...

Foundations of Amateur Radio Our community is full of TLAs, or three letter acronyms. Some of them more useful than others. For example, I can tell you thank you for the QSO, I'm going QRT, QSY to my QTH. Or, thanks for the chat, I'll just shut up and take my bat and ball and go home. Acronyms arise every day and it came as no surprise to spot a new one in the wild the other day, SHF. It was in a serious forum, discussing antennas if I recall, so I didn't blink and looked it up. Super High Frequency. Okay, so, where's that? I'm familiar with VHF and UHF and as radio amateurs we're often found somewhere on HF, that's Very High Frequency, Ultra High Frequency and High Frequency if you're curious. Turns out that the ITU, the International Telecommunications Union has an official list, of course it does. The current ITU "Radio Regulations" is the 2020 edition. It's great bedtime reading. Volume one of four, Chapter one of ten, Article two of three, Section one of three, Provision 2.1 starts off with these words: "The radio spectrum shall be subdivided into nine frequency bands, which shall be designated by progressive whole numbers in accordance with the following table." When you look at this table you'll discover it starts with band number four and ends with band number twelve, between them covering 3 kHz to 3000 GHz. In position ten you'll see the designation "SHF", covering 3 to 30 GHz, centrimetric waves. A couple of things to note. The list starts at band four. There are of course frequencies below 3 kHz. The list ends at twelve, but there are frequencies above 3000 GHz. You'll also note that I'm not saying 3 Terahertz, since the ITU regulations specify that you shall express frequencies up to 3000 GHz using "gigahertz". Interestingly the same document has a provision for reporting interference where you can report using Terahertz frequencies, so I'm not sure how the ITU deals with such reports. Another thing to note is that this table doesn't actually define what SHF means. It's nowhere in the radio regulations either, I looked. I'm not sure where the words Super High Frequency came from. There is an ITU online database for looking up acronyms and terms. That leads to a document called "Nomenclature of the frequency and wavelength bands used in telecommunications", which also doesn't use "Super High Frequency" anywhere. That said, using the ITU band four, where its definition starts, the VLF band, or Very Low Frequency, followed by LF, Low Frequency, MF, Medium Frequency, the familiar HF or High Frequency, VHF, UHF, then SHF and beyond that, EHF, Extremely High Frequency and THF or Tremendously High Frequency, yes, Tremendously High. There's a report called the "Technical and operational characteristics and applications of the point-to-point fixed service applications operating in the frequency band 275-450 GHz". It introduces the term "THF which stands for tremendously high frequency" but adds the disclaimer that "this terminology is used only within this Report." Seems that there are plenty of documents on the ITU website using that same definition, so I'm guessing that the cat is out of the bag. THF by the way is defined as being for 300 to 3000 GHz frequencies. By the way, the ITU TLA finder exposes that THF stands for Topology Hiding Function. Where's a good acronym when you need it? Speaking of definitions, I came across the definition of a "taboo channel" which according to the ITU is "A channel which coincides with the frequency of the local oscillator in the single super heterodyne receiver which is tuned to an analogue channel." Anyway, we still have a way to go. Below band four, less than 3 kHz, we have ULF or Ultra Low Frequency, SLF, Super Low Frequency and ELF, Extremely Low Frequency, which is defined as band one, between 3 and 30 Hz. Below that, some have suggested TLF, or Tremendously Low Frequency which apparently goes between 1 and 3 Hz with a wavelength between 300,000 down to 100,000 km. Others have suggested that this is an internet meme, but so far it seems to me that it has just as much legitimacy as any of the other wordings, since it appears that the ITU explicitly excludes such definitions, even if internal documents introduce terms from time to time. It did make me wonder, what comes after Tremendously High Frequencies, Red? Turns out, yes, well, infra-red pretty much follows on from Tremendously High Frequencies. If you think that's the end of it, think again. The IEEE, the Institute of Electrical and Electronics Engineers has its own definitions, of course it does. Unfortunately they decided that you need to pay for their standard. It was first issued in 1976 "to remove the confusion". There's an xkcd comic called "Standards", number 927 if you're looking. It goes like this: Situation: There are 14 competing standards. 14?! Ridiculous! We need to develop one universal standard that covers everyone's use cases. Yeah! Soon: Situation: There are 15 competing standards. Anyway, the IEEE designates that after UHF comes L or Long wave, followed by S, or Short wave, then comes C, the compromise between Short wave and X or cross or Exotic. Then there's Ku, Kurtz Under, K, Kurtz, and Ka or Kurtz above, Kurtz being the German word for Short. There's the V band and the W band which follows the V band. Had enough yet? NATO, the EU and the US define these using letters of the alphabet. And broadcasters use Band Numbers which link up to nothing in particular. I wonder if the measure of a society is just how many different ways can be used to describe the same thing. Perhaps we should have stopped at Hertz or Hz, which was established in 1930 by the International Electrotechnical Commission, as an expression of the number of times that a repeated event occurs per second, in honour of Heinrich Hertz. One more three letter acronym, the International Electrotechnical Commission is better known as the IEC. I wonder if the ITU is taking suggestions, ginormous, utterly, inordinately, awfully and humongously seem like perfect opportunities for future expansion. I'm Onno VK6FLAB.