[Amps] Maximum RF output in practical application: 4-250A

[Joe Isabella]

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 at subich.com>
To: Joe Isabella <n3ji at yahoo.com>; amps at 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 

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