I know that the amateur bands are not channelized. I know that anyone can pick an arbitrary frequency and they're not wrong, and you are not obligated to have a calibrated VFO. But if everyone picks frequencies at random during a period of heavy usage, there's likely to be inefficient allocation due to not-quite-wide-enough gaps to fit in.
Do there exist, then, any conventions for what frequencies to use, that are more widespread than each individual operator's idea for best practice?
Thinking about this once, I said to myself: SSB is 3 kHz wide, so we can divide that neatly into XXX0000, XXX3000, XXX6000 Hz with only a little bit of waste.
More recently while I was operating on Field Day this year, I noticed a lot of people using XXXX500 Hz frequencies, and it occurred to me that if we consider the bandwidth as 2.4 or 2.5 kHz (as it apparently typically is as transmitted, even if receive filters aren't that sharp) then four channels fit into 10 kHz that way. Is that something people try do? (Reviewing my logs, some but not all of the 500 Hz frequencies fit this pattern.)
But trying to spot the pattern this way is an exercise in numerology. Are there any deliberately promoted, or somewhat accepted, schemes for SSB frequency selection?