[Elecraft] The Dreaded 400 Hz hump

[jerry]

I remember reading a magazine article many years ago... They showed a 
hole of frequencies in the normal human voice audio
spectrum where there is not much energy.  It was proposed to create a 
new modulation where the higher frequencies would be
shifted down into the hole - thus letting the SSB signal take up less 
spectrum - and then shifting those audio frequencies
back up at the receive end.

   Thinking about it...that's the sort of thing I would have expected to 
read in Ham Radio magazine.  I miss it.

                 - Jerry KF6VB


On 2022-05-20 17:10, Walter Underwood wrote:
> About seven years ago, there was an extended discussion on this list
> about equalization settings for transmit. I collected all the settings
> people used and posted about the majority contour.
> 
> https://observer.wunderwood.org/2015/09/09/transmit-audio-and-compression-with-the-elecraft-kx3/
> 
> wunder
> K6WRU
> Walter Underwood
> CM87wj
> http://observer.wunderwood.org/ (my blog)
> 
>> On May 20, 2022, at 6:07 PM, Bob McGraw <rmcgraw at benlomand.net> wrote:
>> 
>> Oh yes it is there on many SSB signals where the OP is a male. That is 
>> where most of the fundamental male voice energy occurs. Those signals 
>> which look uniform across the SSB TX bandpass do sound good.
>> 
>> I attribute this to the fact most hams will "boost this and boost 
>> that" and never give thoughts to attenuating.  In fact the 
>> characteristics of the EQ in the boost mode are noticeable different 
>> than the attenuate mode.  Yes, one can hear the difference.
>> 
>> In my world of pro audio, it is a practice to attenuate first and then 
>> boost if absolutely necessary.   Hams just can't get over the fact 
>> they must always have more.......boost boost boost.
>> 
>> So if ones signal is muddy or bassy, what's to do?   Attenuate the low 
>> end first, and rarely if ever,  boost the high end.  Of course 
>> boosting the high end will make it brighter, but not attenuating the 
>> low end will consume lots of unnecessary transmitter power not being 
>> used for effective communications. 50Hz - 16dB, 100Hz -16dB, 200Hz - 
>> 16dB, 400Hz - 9dB, 800Hz - 0dB, 1.6kHz - 0dB, 2.4kHz +0dB, 2.4kHz 
>> +3dB, 3.2kHz + 6 dB.
>> 
>> Works for me.
>> 
>> 73
>> 
>> Bob, K4TAX
>> 
>> On 5/20/2022 4:30 PM, elecraft-request at mailman.qth.net wrote:
>>> Message: 8
>>> Date: Thu, 19 May 2022 02:14:10 +0000 (UTC)
>>> From: Al Lorona<alorona at sbcglobal.net>
>>> To: Elecraft Reflector<elecraft at mailman.qth.net>
>>> Subject: [Elecraft] [OT] The dreaded 400 Hz hump
>>> Message-ID:<1840135010.161126.1652926450733 at mail.yahoo.com>
>>> Content-Type: text/plain; charset=UTF-8
>>> 
>>> Have you studied how SSB signals look on your panadapter? I believe 
>>> about 90% of all phone signals have a very pronounced peak at about 
>>> 400 or 500 Hz. This peak is sometimes 10 dB (or more) higher than the 
>>> rest of the bandwidth. This is wasted power and, to my ear, makes 
>>> signals sound muddier.
>>> 
>>> On the other hand, every once in a while you'll see a signal that has 
>>> a more or less flat frequency response, without any huge peaks. 
>>> Sometimes, a signal will actually have slightly*more*  power in the 
>>> higher frequencies, say, 2000 Hz and higher. I've noticed that these 
>>> signals have much more articulation and punch. But these signals are 
>>> all too scarce.
>>> 
>>> It's pretty well known that the aging population of hams collectively 
>>> suffers from a high frequency hearing loss. It seems to me that this 
>>> is even more reason to carefully shape your frequency response and 
>>> cut the dreaded 400 Hz hump.
>>> 
>>> R,
>>> 
>>> Al? W6LX/4
>> 
>> --
>> IF ONE EXPECTS COMPUTERS AND TECHNOLOGY TO SOLVE THEIR PROBLEMS,
>> ONE DOESN'T UNDERSTAND COMPUTERS AND TECHNOLOGY
>> AND ONE DOESN'T UNDERSTAND THEIR PROBLEMS."
>> 
>> 
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> 
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