[Elecraft] RTTY Operations

[Bob Lewis (AA4PB)]

> The tone must switch at the zero crossing point or it will
> introduce more harmonics than you can measure.

In the ham community it wasn't until the advent of solid-state digital
components that even AFSK generators began shifting at the zero
crossings. Prior to that most AFSK generators simply used two
free-running oscillators and switched between them. As I recall it
wasn't until somewhere around 1970 that we began to see generators
driven from a single clock and switched at the zero crossing.

I think even today that most of the ham rigs with direct FSK do not
have any circuitry to ensure switching at the zero crossings (at least
the schematics I've seen appear to have no components to accomplish
that).