It has nothing to do with the transmitter, saying you changed to another low band channel in the transmitter is no different than changing to a high band channel, its illegal and potentially dangerous.

High/Low band only applies to recievers, and then, only Futaba and only certian models. They didn't do if for the longest time, and they have quit doing it.

Hiband Loband effects only some Futaba receivers but not all. Note; effects receivers only, not the transmitters. Reason: the receivers are also tuned by internal components and to get sharp tuning, the optimum effective range is restricted. Futaba tunes some receivers to center 1/4 the way into the band and others to tune 3/4 the way into the band. This gives max sensitivity and noise rejection for the receiver.

thanks for the technical readout on how the tx works. i havnt bought anything from th scratch and dent yet but i need to upgrade my tx. i guess i have to wait a while till i get one on my channel (or just buy one on my ch). im in no rush.
i think why people get confused on this topic is when you change a tx channel to another one it works (not as well but that would be hard to notice if doing a quick test), the crystal on some tx's are removable, and the fact that you can buy tx crystals.

It's legal in OTHER countries to change your own crystals. They have different situations to comply with than we do here. TH sells worldwide and also to authorized shops here. There is no reason not to sell the product, it is up to the purchaser to know what is legal for him to do with it. Much like you can buy a gun from a dealer but it's up to YOU to know that it's illegal to kill someone with it. You can buy a Corvette that will drive at 150 MPH but it's illegal to do so on virtually all roads.

This is the part that confuses me. My first radio was 2.4 ghz so I've got no experience with those 72 mhz radios with replaceable crystals. If swapping crystals is so dangerous, why don't other countries have laws against it? And why are the crystals sold? Are planes constantly being shot down outside the US? Or is it mostly the legal issue that stops people from doing it in the US? I saw the post earlier where someone said a plane was shot down due to a bad crystal swap. Is that common? It just seems odd that something that sounds so dangerous is only forbidden in one country.

In the US there are commercial users sandwhiched between the "channels" we use. You can change 50mhz crystals all you want provided you have a ham ticket to operate there as they are the only ones on the band. Honestly the FCC doesn't care about you shooting airplanes down (though your insurance carrier might), they care about interfering with the commercial (read that: PAYING) users of the band.

That situation is unique here, hence the rules. They sell the crystals because there are plenty of shops with techs trained to check the tuning.