I agree with you in this case -- 300 to 3.3k (3 kHz total audio bandpass) isn't
too bad. That's actually much better than most of you actually do on the HF
Amateur bands (I hear 500-2.4k, or 1.9 kHz total audio bandpass often -- and
even less than that on occasion!!). When you extend the top-end to 4k (3700 Hz
total audio bandpass), there are very little ambiguities. I can hear the
difference between "F" and "S", or "P" or "T" with 4k, when listening to
500-2.4k signals, speech is so degraded, it's almost like hearing babies
screeching on an airplane -- after so much of it, your nerves are shot and you
long for some "peace & quiet". Listen to a full-range SSB QSO (50-4k or
better), and it's as if you're having a fire-side chat.
There are times & places for punchy audio, but it's not required all the time.
Full-range audio is great for rag-chewing -- punchy, ice-pick in the ear audio
is not, but is good for contests and DX'ing during noisy, crowded band
conditions. That said, I believe better results can be had by slightly
extending & emphasizing your basic 300-2.8k SSB signal out to 3.3 to 3.5k as I
mentioned before. Going beyond that may or may not help since most don't
bother trying to listen out that far. There has been a lot of activity
recently regarding extended speech capabilities of voice systems (up to 6 or
even 7k), to the extent that the Bell Labs research from 50 years ago can be
shown as a compromise, which is what it is (balancing accepted loss of speech
intelligibility with analog NW resources). The popular VoIP PC-PC SW is *MUCH*
wider than 2.5 or 3k. Digital networks and new types of speech coding make
that compromise unnecessary. Consider that you can get up to 53.3k of
data in on a dial up modem -- even half of that yields incredible speech data
rates. To compare, cellular phones vary from ~12k of coded speech data down to
4.5k, depending on the RF conditions. In other words, you could double SSB
speech BW using digital, and still double or triple phone system capacities
from 300-3.3k analog channel baselines. Combine variable speech coding with IP
packet networking, and it becomes very efficient, only sending packets when you
talk. The average person only talks for 35-40% of the call, making dedicated
analog channels 60-65% wasted. But I digress... Simply, 50 year old Bell Lab
research is just that -- dated & not relevant to current systems.
Joe, N3JI
----- Original Message ----
From: "Joe Subich, W4TV" <w4tv@subich.com>
To: Joe Isabella <n3ji@yahoo.com>; amps@contesting.com
Sent: Monday, July 3, 2006 4:32:25 PM
Subject: Re: [Amps] Maximum RF output in practical application: 4-250A
> On the contrary, Joe. I can prove humans can tell the difference
> between certain letters, words, and sounds with 4k of audio that
> you can't with 2.5k.
You may be able to prove that humans can distinguish certain letters,
words and sounds with 4K audio that they can't with 2.5 K. That's
not the issue. The issue is that Bell Labs and other competent
research facilities have long proven that communication is substantially
unimpaired in a 2.5 to 3 KHz bandwidth and additional bandwidth does
not contribute to significant improvement in reliability. The ITU and
national regulatory bodies have recognized that and have designed
most regulations around a 3 KHz bandwidth for voice.
> You show me what FCC rule says I can't run 4k of SSB audio in the
> Amateur spectrum given the available space, and I'll concede.
Perhaps the FCC hasn't explicitly stated that 4 KHz is "illegal" - I
believe the use of audio bandwidths greater than 3 KHz is not in
keeping with good engineering practice which would be in violation
of the rules. This is exactly why the ARRL proposal to regulate
emission by bandwidth is needed - to address both the "all knobs
to the right" and the selfish "I need 5 KHz audio" attitudes.
> Until then, you're wasting time and "bandwidth".
As you are wasting a far more scarce resource ... amateur spectrum.
73,
... Joe, W4TV
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|