I'm puzzled by this claim. I wouldn't call it a myth, but all the same...
I grew up on a vineyard. Each harvest time the grapes would hang down heavily and almost touch the ground. Our pet dogs would park themselves beneath and greedily consume a whole bunch.
They would also scoff any dried grapes they found on the ground.
The worst effect seemed that they all would get noticeably pudgy during the season.
Transmitters need only be re-certified if they are to be sold in quantity.
Once-off Broadcast Transmitters need only demonstrate that they meet the relevant standards.
Many of the existing LF and MF BC transmitters were effectively custom built to meet the requirements of their transmit license (for example, the radiation pattern of the antenna were often unique for each station).
The "Woolyness" of AM broadcast (at least in America) is due to the stations purposefully tailoring their audio processing to suit typical cheap AM receivers. And this in turn is because designers of cheap AM receivers fit narrow filters instead of using noise reduction techniques, eg a good outside antenna.
There was a period (in the rest of the world) where high quality AM receivers had a narrow/wide switch to give better audio response to stronger signals.
The good news is that modern SDR receivers usually have selectable bandwidth on AM so as to derive the full transmitted audio. And many of these have AM stereo decoders as well.
If you listen to a good quality AM broadcast (eg Gov AM stations in Australia) you will hear audio which are very hard to tell from FM audio.
Go back and read the many high-quality AM tuner articles in the electronic hobby magazines from the past.
This is a myth. There is no reason that channel spacing need limit the modulation bandwidth. The only downside is that listeners to adjacent stations will hear a slight "monkey chatter" from the overlapping sidebands. In reality stations are never allocated adjacent frequencies within the same coverage area so this usually doesn't happen.
There were a number of successful AM stereo broadcasting methods proposed and trialed. These were completely compatible with conventional AM transmissions.
The conceptually simplest of course whas where the LSB and USB are used as separate channels.
Although most of the systems did work, they were not ultimately successful simply because insufficient stereo receivers reached the market.
There is no reason that the channel spacing need limit the sideband bandwidth.
The only downside to this is that listeners on adjacent stations hear a slight "monkey chatter" from the overlapping sidebands.
This is one of many reasons why station frequencies are never allocated close to stations which are physically close.
You only need glance at the waterfall display on a good SDR receiver to see that the actual audio bandwidth is often much wider than the channel spacing implies.
Fessenden is famous for developing a electomechanical RF generator which put out a clean sinewave (eg a coherent wave), which helped replace the earlier Spark-Gap systems (which generated wide-band hash).
There are simple exercises that you can do while seated to avoid DVT. Just wriggling your toes help a lot, or flexing the muscles in your legs.
I fly a lot on routes over the tropics and have experienced serious turbulence multiple times. There's no way I will be wandering around the cabin unnecessarily.
I grew up on a vineyard. Each harvest time the grapes would hang down heavily and almost touch the ground. Our pet dogs would park themselves beneath and greedily consume a whole bunch.
They would also scoff any dried grapes they found on the ground.
The worst effect seemed that they all would get noticeably pudgy during the season.