AM = amplitude modulation (as opposed to frequency modulation). It has nothing to do with a specific frequency range.
In the United States for example, AM is commonly used from ~150khz all the way up into the low hundreds of megahertz.
As an example, all aircraft transmissions in the US are AM and are in the ~120-130Mhz range.
Thanks for explaining that to me, a licensed amateur radio operator for more than 20 years. :p
I meant the AM radio broadcast band as an example of a popular use case of radio in the early days when the "high frequency" designation was made.
They are extremely low frequency compared to where most radio communication occurs today, orders of magnitude higher. Not literally ELF, which isn't used apart from extreme niches.
> a licensed amateur radio operator for more than 20 years
Every HAM I know would ridicule me if I used such wording as you did, which I feel I didn’t do, maybe your experience is different.
My reply was less in explaining it to you though, but more as being informative to others who might’ve not had the experience and thus could learn misleading information from your post.
(I’m also a licensed operator, but not for as long as you)
AM radio stations in the US are from 530Khz to 1700Khz, so possible. If so, then calling them “extremely low frequency” is a bit of a misnomer, as that band is called “medium frequency” or MF for short. The actual ELF band is 3-30hz, 4+ orders of magnitude lower frequency, and is mostly only used for submarine communication as most higher frequency signals are filtered by water.
My point is that the basis for the designations were made in a period where AM radio was the primary use case for radio and so frequencies higher than the AM radio band are called "high frequency," whereas today those frequencies are actually much, much lower frequency than nearly all forms of radio communication.
The name MF/HF/VHF etc were defined by ITU v.431 originally in 1953. Amateur radio operators in the 1950s commonly were using “shortwave” frequencies (now referenced as HF commonly). As it’s been told to me from multiple operators in that era, the naming scheme used by ITU for each group is based on the amount of bandwidth available in each group, not based on any presumption of AM radio broadcasts being used as a baseline.
In the United States for example, AM is commonly used from ~150khz all the way up into the low hundreds of megahertz. As an example, all aircraft transmissions in the US are AM and are in the ~120-130Mhz range.