FreeDV

[Robert E. Seastrom]

"fgentges at mindspring.com" <fgentges at mindspring.com> writes:

> I did see at one point where one of the FreeDV authors said his system was
> working well at 30 watts average.  That seems high but maybe it is a good
> setting.  I want to do some tests and see a scope of the waveform as it goes
> into clipping.

The problem there is that "working well" is pretty subjective.  I
presume he means he's gotten good copy, but may entirely overlook what
he's doing to his neighbors or that due to wasted energy by not
transmitting "pure" tones he might have been better off at 10 watts
than at 30.

I'm sure we've all seen PSK signals that are ringing all over the band
rather than looking like a nice clean little railroad track going down
the screen.  Funny thing was, it still had good copy despite being a
mess.  It's amazing how wrong things can be and still "work well".

The usual way people lose in PSK-land is by overdriving the audio
stage.  I'm not an expert in the analog domain but it would seem to me
that the same pitfalls for the power amplifier also exist in the
microphone amp and that FreeDV users ought to be careful there too.
Frank, is this a valid concern or have I overlooked something?

-r