Here is roughly what you find in the US on VHF:
VHF starts at 30 MHZ and extends up to 300MHZ or ten
meters down to 1 meter.
In all the Americas, 30-50 MHZ is public mobile radio of
all types. This includes lots of commercial two-way radio and
paging applications, emergency services, marine and even
military frequencies.
50-54 MHZ is the 6-meter amateure band. 54-72 MHZ is TV
Channels 2-4. Here is where it gets kind of odd.
72-76 MHZ is what is called point-to-point radio. It is
an amateur band in Europe or at least some parts and maybe
Gordon Smith has been on that band, but we do not have it as an
amateur band here. What we have, here in 72-76 MHZ is a lot of
unusual uses. Radio controlled models use a number of channels
in that band. Broadcast operations use frequencies for cuing
systems.
These are low-powered transmitters that a broadcaster
might set up at some public event or at the site of a remote
broadcast so that they can coordinate their crew. Frequently,
the transmitter is a narrow-band FM transmitter in which you
hear the broadcast audio plus directors and producers speaking
to the crew to alert them on being ready for whatever is
upcoming in the broadcast. It's interesting listening especially
when something goes wrong and folks get snappy.
Also 72-76 MHZ is used for hearing augmentation systems
such as are found in classrooms and auditoriums.
Hearing-impaired people can listen on a special FM radio to
whatever presentation is going on without all the echo and
background noise you normally hear in a large auditorium.
Churches may also own these augmentation systems so it
is not uncommon to hear them in this band.
The 72-76 MHZ band is also used for multi-point
distribution systems by some paging networks. They have one
transmitter on a frequency in this band and then deploy what are
essentially repeaters all over town which listen to that one
frequency and retransmit that signal on frequencies that are
authorized for paging. It keeps designers of such systems from
having to run telephone lines all over town to carry the same
signal. In short, there are a lot of low-powered signals in this
band for special purposes. Also, 75 MHZ is used by instrument
landing systems at airports all over the country as a beacon
frequency to assist planes when doing instrument landings.
Back to the rest of VHF, 76-88 MHZ are TV channels 5 and
6 which is why you don't hear anything any more. You used to
hear the buzz of video and the FM sound carriers which sounded
just like FM broadcast stations when one tuned across them.
There are almost no television transmitters in the United States
on 54-88 MHZ since we went digital but the few hearty television
operations that did stay there are all digital so you will just
hear hiss.
Starting with 88 MHZ, there is the FM broadcast band
which is pretty much the same all over the world except that
some countries like the UK and many others in Europe use
frequencies ending in even numbers like 90.0 MHZ or 102.2 while
others like the US and Canada end in odd numbers such as 88.3 or
99.5.
The FM Broadcast band ends at 108 MHZ and we go to
aviation between 108-136 MHZ. All those signals are AM.
Above 136, there are a number of frequencies used by
satellites such as weather facsimile and telemetry.
There are military frequencies between 138 and 144 MHZ
and then the two-meter amateur band up to 148 MHZ.
Above that are more military frequencies and some more
satellite down-link telemetry up to 150 MHZ.
Our VHF high public mobile frequencies start from 150 to
174 MHZ and that band is full of everything you can imagine plus
a lot more from emergency services to hearing augmentation
systems, broadcast cuing and weather broadcasts.
Finally, 174-215 MHZ are TV channels 7-13and those
frequencies used to be analog TV but are now all digital.
Above that are some more military frequencies, special
public mobile allocations and then the 222-225-MHZ amateur radio
band.
Everything above that and extending up to 400 MHZ is all
military air activity.
Personal observations: The 30-50 MHZ band is rapidly
becoming a dynosaur. Nobody in their right mind wants to have an
allocation especially between 30 and 40 MHZ because of Sporadic
E skip and F2 ionospheric propagation which means you might not
be able to contact your delivery vehicle 20 blocks away but some
taxi cab service in Argentina or Bogata, Columbia is blowing out
your speakers and probably cursing you in Spanish because this
English voice keeps calling Unit 5 asking if they have delivered
that load of gravel yet.
Emergency services by the boatload are moving out of
that band and going to UHF where conditions are somewhat more stable.
There are still things to hear there, but not nearly as
much as there used to be.
Martin
Travis Siegel writes:
> Oh, one more question.
>
> Does anyone know what's just under the fm band (88-108 on the fm band in
> the us)
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