I often consult tables to determine where a station I'm hearing is located. I use them to answer questions like "TF, that's Iceland, right?" or "4X, where is that?".

In every table I've found, the prefixes are upper case, except some of them contain a lower-case 'o'. For instance, FOo belongs to Austral Islands and HBo belongs to Liechtenstein.

From how they are positioned, it would make sense to read them as zeroes, but then again some other prefixes are printed with zeroes. For instance, both this and this table say KH0 belongs to Mariana Isl., though they also list the o-prefixes.

What's going on? And why?

Is it a simple matter of someone using the convention of 'o' for zeroes once, everyone copying that table without checking it, and then adding prefixes with zeroes without realising there's a conflict?

Or have I completely misunderstood, and the lower-case o's mean something completely different?


1 Answer 1


From what I can find, it appears those lowercase o characters are indeed supposed to represent zeros. Aland Island, as one example, is indeed OH0, and is listed as OHo.

My guess is they came from some source material where there was no obvious distinction between zeroes and the uppercase letter O. Back in the days of typewriters that could be a problem. Some typewriters even expected you to use lowercase L for the number one, and uppercase letter O for zero and didn't even have separate keys for them.

Today with computers where you can use a font that makes an explicit difference, it isn't as much of a problem.

  • $\begingroup$ In some fonts, the numbers are designed to appear like lowercase letters: see en.wikipedia.org/wiki/Text_figures or fonts.com/content/learning/fontology/level-3/numbers/…. My guess would be that the original source material used that typesetting style, where a 0 as part of a longer number would be clear but on its own when mixed in with capital letters ends up looking like a lower-case o instead. $\endgroup$ Oct 24, 2022 at 19:14
  • $\begingroup$ "In some fonts, the numbers are designed to appear like lowercase letters" That is not the case here, as the table referenced has both zero and lowercase O characters in it. These are indeed lowercase letter O's. I'm fairly sure this data originated in a typewritten table in the days predating personal computers. $\endgroup$
    – John
    Nov 18, 2022 at 0:10

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