What's a question you have that Google can't answer but maybe somebody on reddit can ?

Yes. It's due to how use of the electromagnetic spectrum is assigned in the US.

In traditional over-the-air television broadcasting, all the low channels were in a band region called VHF. There were originally only 13 channels. (This is the origin of the Pink Floyd line, "I got thirteen channels of shit on the T.V. to choose from" -- "Nobody Home", The Wall). FM was assigned right above that -- and I might right above, with nothing else in between. If you had a full- or wide-spectrum receiver, and worked your way up the dial, you'd pick up the audio from those 13 channels (later called "VHF Low" after more VHF channels were added later) and then you'd reach the bottom of the FM band.

In older analogue FM tuners, if you go all the way to the bottom of the FM dial, you used to be able to pick up the audio from the highest VHF-Low TV station, Ch. 13. I used to listen to all kinds of TV while doing delivery. Nearly all the Seinfeld I've ever "seen" I actually only heard, and a testament to how well it was written was that it works fine as a radio show. (Though there's plenty of visual humour, most of the gags are in the dialogue, and there's no problem following the plot.) I also heard several episodes of a TV show I've still never actually seen, called Grace Under Pressure.

This doesn't happen any more, even with older analogue FM tuners, following the DTV conversion in February 2009, when nearly all analogue television in the US converted to digitally encoded modulation with somewhat different spectrum allocation: VHF-Low no longer 'bleeds' as high as it used to, so you can no longer pick it up. (The only exception would be some remaining LPTV (Low-Power Television) assignments which were not forced to convert, though I don't know if any are assigned or even allowed in the top end of VHF-Low. (This has mostly to do with my general ignorance about television. My background is in FM, which is the only reason I know about this.)

That's the answer to your question, but I'm going to go further.

When more VHF stations were allocated, they couldn't be assigned next to VHF-Low, because the spectrum below and above it had already been assigned. (The latter, explained above, to FM.) They were instead added above FM. The entire FM band sits between VHF Channels 13 and 14.

So you might be wondering, could you have picked up Ch. 14 at the top of the FM band? The answer is no. The reason is that although VHF-High is above the FM band, it's not right next to it, and never was. The present allocation scheme has FM topping out at 108 MHz and VHF-High starting at 174 MHz. In between are several other services. Most notably, aircraft radio, which is allocated in the range 108-136 MHz.

So, were you ever able to pick up aircraft radio at the top of the FM band? Sort of, but not really. Though there was nothing stopping your old analogue FM receiver from picking up those transmissions, they were usually too weak for you to hear. Aircraft radio is typically much lower power, and so range is much more limited.

What's specifically relevant to both FM and aircraft radio, though, is that US Air Traffic Control bands are right above the FM band. And that fact has gotten a lot of careless radio pirates in a lot of trouble.

There are different kinds of radio pirates. Those who know what they're doing, who understand the spectrum and the FCC and the technical principles of radio, will probably never get caught, and if they do, they are not likely to get in serious trouble. Despite stereotypes, the FCC doesn't really care about most radio pirates, especially these guys.

They don't even necessarily care much about the sloppy ones. But ATC sure as hell does. Basically, if you're a radio pirate and you get caught by another radio broadcaster, and the FCC checks it out and finds you, you can expect a stern talking-to, maybe even a strongly-worded letter or two. But unless you're a total dick to them, you're not likely to face forfeiture (fines) or other penalties, because it's not worth their while unless you're really making it hard for licensed use of the spectrum, or you just won't quit and keep making trouble, or you give them some good reason (such as being a dick). But if you get caught by a pilot or Air Traffic Controller, you can expect to have your door kicked down, and get cuffed and stuffed and hauled off to federal court. The difference, of course, is between irritating broadcasters trying to sell soap, and posing a threat to public air safety.

The sloppy ones fail to use something called a high-pass filter. As you may know, especially if you play an instrument, every primary tone also creates harmonics, all the way up the scale to infinity (or at least to the Planck Length). The power of the tone drops on its way up, but it's still there, and at some point simply falls below detectable limits. The 'noise' you hear on the airwaves is made up of lots of things, but the disorganized harmonics of every signal out there crashing into each other is part of it. Most of that's not a problem. But in the range not too high above the primary, harmonics can be strong enough to cause unacceptable interference. A high-pass filter chops off all frequencies coming out of your rig above a pre-determined limit -- say, maybe 108 MHz. Without that, there's nothing to stop your sooper-seekrit pirate station at 107 MHz from blasting your favourite shitty music or hilarious conspiracy theories to whatever pilot happens to be going overhead at that moment, assuming you're also not smart enough to use low power. (The stronger the signal, the easier it is to find.) When you hear about radio pirates getting frog-marched to jail, they're almost always one of those fools.

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