> > 100 Hz audio will be rejected by my receivers that roll off
> at about 300
> > Hz and so is again wasted energy. The original gurus of
> SSB, Papenfuse,
> > Bruene, and Shoeneke, said roll 'em off at 300 Hz (partly
> because the
> > analog filter slope also is relatively gentle and the added
> attenuation
> > of putting the carrier 20 dB down the slope helps need carrier
> > suppression specs) because you don't need lower frequencies for
> > communications. Ma Bell did that for long lines as well as
> for handsets
And that's why "toll quality" audio, and radios that produce toll-qualtiy
audio sound like cr*p.
A rule of thumb is that the LF cutoff times the HF cutoff in Hz, should be
about 400,000-450,000 to produce "balanced" sounding audio, in the sense
that lows and highs have a natural sounding balance. I agree that you don't
need LF response to 20Hz, but good clean response to at least 100 Hz is not
a bad thing if you're running the O at full bandwidth.
If the low-end cutoff is indeed 300 Hz, the highs should cutoff at 1333 Hz
for "balanced" (but totally useless) audio. If the highs go to 2.4 Khz, a
typical number, the low end should extend to around 170 Hz.
Fortunately, newer technology telephony systems (depending on Codec of
course) can yield far better frequency response than what Ma Bell had in
mind.
Grant/NQ5T
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