.
.
Actually, you can use FM in any band segment that allows 'phone- as long as it stays within the bandwidths specified in Part 97.307.
In essence, that says if its narrowband, it permissible below 29.0 Mhz., but no angle-modulated emission may have a modulation index greater than 1 at the highest modulation frequency. Since no one operates NBFM (at least I've never heard it on amateur HF... although I have used it very sucessfully on non ham frequencies) this standard is quite obscure.
.
FM, as we know it, is semi-popular on the upper end of 10 metre's- 29.6 is the calling channel, and there are a number of simplex and repeater frequencies clutter'd about it. Simplex can be quite useful when the band is quiet- the longer wavelength gets into valleys and around hills and mountains much better than V/UHF.
When I was doing field work, our vehicles used lower-low band FM mobile to mobile, almost exclusively for our simple communications. No repeaters, just 100 watt radios to quarter wave whips- the range was often 80-100+ miles over the deserts of Nevada-
.
But when there is 'skip' this usefulness can go into the toilet. 29.6 will come alive, and with everyone stepping on each other the frequency rapidly becomes a muck. The nearby simplex channels fare better-- but the repeater channels become one cacophonous squabble of noises as signals from multiple continents garble each other on the repeater inputs.
I know there are the 10 metre repeater aficionado's out there, and I don't want to engage in a debate- but today the concept of an HF (Ten should be consider'd HF for all practical purposes) repeater makes no sense to me.
.
One of our work band of frequencies was in the 33Mhz segment. With the mass exodus of everything low band VHF this was perfect- we had the place to ourselves-- that is, except when there was skip. One of our channels we called SPC - the "Somali Pirate Channel." We never could figure out where these guys were coming from, but there was always boat noises and very animated conversations when they came on- we figured they were pirates out chasing a cargo ship, or something.
We couldn't understand a word they said.
Fortunately we'd flip to another frequency.
.
.
While I am on this 10 metre subject- don't overlook 29.000Mhz, the low power AM calling frequency. It goes back many years to the days of 'hacking' CB radios to Ten (do people still do that ?)
I have had some suprising conversations on 29.0 AM from out in the Central Pacific- spanning several thousand miles- back when the Sun Spots smiles.
Clustered about 29.000 at 10Khz intervals are some alternate AM simplex channels.
If 10 opens its worth a listen.
.
.
.
Lauri
.
________________________________________
PS..
I just posted this and realized I mirror'd Token's comments-- proof Great Minds think alike ... lol...
.