
Why Do FM Frequencies End in an Odd Decimal? (2015) - pizza
https://www.fcc.gov/media/radio/fm-frequencies-end-odd-decimal
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cbanek
Another interesting note about the FM frequencies is stations from 88 MHz to
92 MHz are the non-commercial part. That's why you'll find a lot of NPR and
religious stations at that part of the dial rather than the other end.

(Looked up after many hours of road tripping through states with very few
radio stations)

[https://en.wikipedia.org/wiki/Non-
commercial_educational_sta...](https://en.wikipedia.org/wiki/Non-
commercial_educational_station)

~~~
anyfoo
Worth noting that that's not a thing in Europe, at least in Germany I don't
remember any differences across the entire band (87.5 to 108 MHz there).

Where exactly the band is and its channel spacing generally differs a lot
between countries.

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closeparen
This article is on the website of the US telecommunications regulator. I'm
don't think all the comments need to be qualified with "in the US."

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seszett
I think the parent was still an interesting comment. What it said was indeed
worth noting.

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unixhero
Norway killed its FM transmission, a perfectly functioning technology. Pure
one to many distribution perfected over time, deprecated.

DAB+ radio has much lower range and the signal is unstable.

To make matters maybe even worse, HAM radio operators at work inform me the
DAB+ standard isn't going anywhere and that the development has mostly
stopped. Maybe somehow 5G can do some marvels for the technology, time will
tell.

~~~
LeoPanthera
I'm normally pro-digital over anything analogue, but broadcast radio is one
medium, possibly the only medium, where analogue is better.

Digital compression simply doesn't cope with packet loss well enough to be
practical. Even with a very weak FM signal, in emergencies you can still hear
through the noise.

~~~
RandomBacon
In rural places in the US, it's terrible for television. Several years ago, it
was mandated that TV stations switch from analogue to digital.

Now instead of getting a little static and being able to understand 100% of
what is said and shown over the air; it's now 10% recognizable video 90%
visual blocks, and 0% audio.

~~~
jdofaz
If the digital transition hadn't happened I think over the air television
might have died by now. Analog broadcast used significantly more electricity
and fewer and fewer people would be interested in the low quality signal.
Stations might have decided the remaining viewers weren't worth the power
cost.

That said I think streaming might kill it anyway.

~~~
toast0
What's the difference in power for analog vs digital TV broadcast?? Is that
mostly because ATSC broadcasts moved towards UHF, and NTSC broadcasters
preferred VHF when available? Or is there some other property of ATSC
broadcasts that require lower energy?

~~~
LeoPanthera
Analogue video has to have a very high SNR at the receiver, because any noise
is directly visible in the picture.

But with a digital signal, as long as you can distinguish individual bits, the
picture is always perfect, so you can get away with a much lower signal
strength.

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Neil44
Here in the UK you get stations ending in any decimal. Other countries have
different schemes. It’s a thing when you import a car from Japan for example,
the FM bands are different so you have to swap the radio or buy a little band
expander box to fudge it.

[https://en.m.wikipedia.org/wiki/FM_broadcasting](https://en.m.wikipedia.org/wiki/FM_broadcasting)

~~~
RachelF
In the US, you only get 200kHz between stations, while other countries
allocate 300kHz spacing, giving them slightly more bandwidth.

~~~
anticensor
100kHz signal bandwidth+100kHz guardband actually.

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phire
I once had a car radio which enforced this rule. Wouldn't tune to anything
except odd decimals.

And it worked fine in my home city, every single radio station was on an odd
frequency.

But I don't live in the US. One day I went on holiday to another city, and in
that city and 90% of radio stations were on even frequencies. The poor radio
refused to tune into them. You could set it to the neighbouring frequency and
get it half tuned in, but it would never lock.

~~~
lokedhs
In all the car radios that I've had, I can tune it to a 20'th of a MHz. So
it'll go from 102.0 to 102.05 and then 102.1.

I've never had anything lock up on those .05 frequencies though. I wonder if
it's every used anywhere.

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el_isma
You're just not going fast enough.

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crymer11
If anyone is interested in amateur radio in the US, don't let the current
situation dissuade you. There is at least one VEC now offering completely
remote exams - I just took both my Technician and General exams with GLAARG
completely remote.

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nullc
Any idea if GLAARG is in need of more VEs to conduct remote tests? I'm an
extra in the bay area and know a couple others who would be willing.

~~~
crymer11
No clue - I barely got the chance to speak with any of the VEs; I joined the
call, showed them my testing environment, took the exams, then they quickly
reviewed results and next steps before leaving to start the next candidate's
process. They had a day full of reservations to take exams and a pretty large
waitlist of people waiting to squeeze in when they had extra time.

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SamReidHughes
The article doesn’t say it explicitly, but it’s because the FM band is bounded
by round numbers, 88 MHz and 108 MHz, as opposed to 87.9 and 107.9.

~~~
ac29
Er, that's in the first sentence. What could be said a little more clearly is
that the frequency 90.1 is actually the channel 90.0-90.2 since the convention
is to tune to the center frequency. A convention of tuning to the lowest or
highest frequency of the channel would be equally valid - its just not how its
done.

~~~
jeffdavis
If you tune to the lowest frequency in the channel, wouldn't that be bad
because it's on the border with the channel just below it? Tuning to the
center of the channel seems like the only sensible thing to do, it's not just
a convention. Or am I way off here?

~~~
ac29
All I mean is that in the modern digital world, there is no difference between
a channel being defined as 90.0 + 200kHz, 90.2 - 200kHz, or 90.1 +- 100kHz.
"Tuning" isn't even really a thing in modern SDR receivers that can receive a
huge band all at once (it is, but more as a UI convention than an analog
necessity).

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jeffdavis
The article doesn't really answer why. It basically says that FM is
channelized first and then the center frequencies are determined; while AM is
assigned center frequencies first.

But why are AM and FM different here?

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wl
Mediumwave AM broadcast uses the center frequency as the channel identifier,
same as FM.

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gpvos
FM channel numbers didn't really catch on, but I do remember that they were a
small thing.

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Aloha
its more interesting that FM stations have channel numbers, which are
basically not used by anyone except the FCC.

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taneq
Same with analog TV stations, I never understood why they use specific ones.
Why channel 7, 9 and 10 but not 8 or 6?

~~~
anyfoo
By the way, in Europe, even for analog TV the channel numbers have been
relatively hidden since at least the 80s. TVs would instead be "programmed" to
have sequential program numbers, which behind the scenes pointed to actual
channel numbers. The channel a station was on could differ widely between
regions, so the channel number was just a local implementation detail. There
is/was also usually some more or less common order of stations, e.g. in
Germany you'd always put ARD on 1, ZDF on 2, the regional "third" station on
3...

~~~
kd5bjo
For a long time in the US (maybe still?), the vast majority of the schedule
was set by the local station. Being a member of one of the national networks
brought access to a catalog of shows, and a few requirements about the
scheduling of shows that the network really cared about. In almost every
nationally-produced promo you got the phrase “check your local listings” in
addition to the advertised time because the local station might air the show
sometime other than when the network recommended.

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drmpeg
FM stations broadcasting HD Radio are 400 kHz wide.

[http://www.w6rz.net/fmbandzoom.png](http://www.w6rz.net/fmbandzoom.png)

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Venkatesh10
Not in India atleast, we have fm stations at 93.8, 106.4 and so on.

~~~
kiwijamo
Same as in New Zealand (NZ). Plenty of even frequencies here.

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reaperducer
It haas nothing to do with quantity or scarcity of frequencies.

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jedberg
When I was a kid we replaced our radio and got a fancy one that could go in .1
increments, which let us hit the even numbers.

It was nice to be able to get far away stations by hitting the even numbers as
long as there wasn’t a neighbor station.

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delecti
I suppose "frequency modulation" (FM) _would_ mean that you'd need to separate
frequencies so each station can "modulate" without running into the neighbors.
That's quite a satisfying thing to learn.

~~~
deepspace
Well, that is an intuitive way of looking at things, but ANY signal carrying
information has non-zero bandwidth. Even an AM (amplitude modulation) signal
occupies a band of frequencies.

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_bxg1
Something I've always wondered is where the channel "names" come from. The
ones that are usually 4-6 characters, seemingly random, often starting with K
or W for some reason. Like KVUE or W2XMN or KLTY.

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pansa2
These seem to be commonly used in the USA - are they used elsewhere?

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anyfoo
Personally haven't seen them anywhere else at least. While the stations might
or might not have call signs on paper, they are certainly not used in any way
a listener would notice. (Of course I can only speak for the countries I've
been to.)

~~~
reaperducer
In Canada, you hear them all the time. Like CFOX/Vancouver, or VOCM/Saint
John.

In Japan, as well. JODW/Tokyo, and others. The only exception I've heard in
Japan is Eagle 810, which operates from a U.S. military base.

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jhallenworld
Why are the AM channels spaced 9 KHz in Europe? You need to be careful when
you buy a low cost car radio due to this..

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fortran77
Not in Europe.

