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[TenTec] Mics in general

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Subject: [TenTec] Mics in general
From: SteveBaron@starlinx.com (Steve Baron - KB3MM)
Date: Fri, 1 Oct 1999 19:30:48 +0100
Have you ever looked at the the 705 implementation.

Those elements typically are very flat response and put out a fairly low
level signal - wonder if that is what the 705 implements

-----Original Message-----
From: JEFF S JOHNSON <aa8ve@juno.com>
To: tentec@contesting.com <tentec@contesting.com>
To: <tentec@contesting.com>
Date: October 01, 1999 7:43 PM
Subject: Re: [TenTec] Mics in general

>Well said Carl, You can't put 50 pounds of potatoes in a 10 pound sack!
>Another thing to remember is the freq. response of the rig audio to rf
>output ratio. I've done some playing around with an audio generator
>running it directly into the mic. input and sweep it through the audio
>span. That way I can watch the ALC and rf power curve and peak at various
>frequencies like a rise starting at 300hz and peaking at 1200 to 1500hz
>then slop down at 3500 or so(which would match the window of a 2.4kc
>receiver as well). Then run the audio generator through an amplifier and
>speaker into the mic. plugged into the rig with ALC and all setup
>properly and sweep the audio up again and see where the peak rf output
>is. If the mic. has the same rise and fall as the rig then I would think
>it's a good match as far as being efficient.  Another  way to look at it
>is do the same thing using the square wave in the generator and watch the
>envelope on a scope.  As for being efficient with the response of the rig
>audio pass to rf output I can see a difference. Now I don't know how
>proper this test is but what I see does match with a lot of things I hear
>about mics, like I tried a D-104 the peak was a bit high, Yeasu desk mic.
>peak was lower, Turner 2+2 pretty darn good, and yes the TT705 was best
>of the ones I have. One can see that the audio response of the mic. does
>have an effect on the rig and the received sig. on the other end.  I
>think the 705 is well matched to a Ten Tec rig as far as typical audio
>response.  Those with voices ranging above or below that can benefit from
>different style mikes to bring their voice into a more efficient part of
>the spectrum.   Now all this has little to do with sound or fidelity but
>more with ssb efficiency.  I've always thought of good ssb audio as good
>telephone quality not broadcast quality and for those who enjoy good
>broadcast quality equipment there are a lot of great ol' AM rigs which I
>enjoy as well.
>Wow, didn't mean to run away with this, I guess it don't take much to
>thrill me!
>73   -Jeff-    diddlede dardedar
>On Fri, 1 Oct 1999 07:36:36 -0700 (PDT) Carl Hyde <cshyde@yahoo.com>
>> I also tried several mics and use the TT 705.  I
>> bought  a demo unit from Ten Tec.
>> I understand the Heil is coming out with a
>> modification to their mic to enhance its performance
>> with the Ten Tecs.
>> The problem with evaluating microphones is the
>> subjectivity of listening to a transmission and the
>> misconception that many hams have of what a signal on
>> single sideband should sound like.
>> In order to keep a narrow 2-3K bandwidth most Ham
>> radio manufacturers design their microphones and audio
>> input circuits to roll off the response below lets say
>> 600hz and above 3000 hz. Most mics have a relatively
>> flat response in the range of the human voice within
>> the rolloff.  The D-104 is one exception to this rule.
>> If you look at the response curve of a D-104 it has a
>> curve that gives low response from about 600 up to
>> about 1700 hz then flattens out in the upper range
>> beyond 4000Hz.  This is because the D-104 ever since
>> the CB craze of the seventies, has been and is
>> designed for CITIZENS BAND radios which use AM not FM.
>> However many hams feel the D-104 sounds good on SSB.
>> SSB is not supposed to sound like an AM broadcast.  It
>> is supposed to allow voice communications within the
>> narrowest bandwidth possible to conserve power and
>> spectrum. So a microphone that uses as little
>> bandwidth as possible to allow intelligable
>> communications is the goal manufacturers shoot for.
>> Hiel's philosophy is a little different.  They offer a
>> couple of different plug in elements that have two
>> different frequency responses, one intended for
>> ragchewing and the other for DXing. Hiel's DX
>> cartridge peaks up the higher frequencies to give a
>> crisper sound to the human voice that is supposed to
>> help in breaking into a pileup by actually making your
>> voice harsh. The purpose is to penetrate the pileup
>> and get you noticed. The H-4 is flatter with more mid
>> frequency response and sounds like a normal and
>> pleasant SSB voice signal. So Hiel recognizes that
>> there are advantages to playing with the frequency
>> response curve for different effects.
>> So every one of us has a feel for what we consider
>> good audio and that feel is very subjective. When
>> evaluating someone's audio consider the goal of single
>> sideband transmissions, Intelligble Communication in
>> the narrow bandwidth available to SSB. So if the voice
>> is clear, not mushy, not breaking up, not distorted
>> and you understand what is being said then the
>> microphone is doing its job. Its not supposed to sound
>> like an AM broadcast or an FM deejay. That defeats the
>> goal of SSB. To include the full range of human speech
>> would require a bandwidth from 300 hz to about 7000
>> Hz. This would waste spectrum and its not necessary
>> for intelligble communications.
>> Now another observation I have made is that microphone
>> choice is especially critical if you are a female ham
>> (YL). The female voice is on average a full 800 to
>> 1000 hz higher than the average male voice.  This
>> presents a problem if the microphone has a low
>> response on the low end and boosts the high end of the
>> curve. If you are a YL or you share your rig with a YL
>> you may need to evaluate another microphone that has
>> better low to midrange performance and rolls off the
>> high frequency better.
>> OK class, the Lecture's over your reading assignment
>> is to go to Hiel's websight and read all about
>> microphone characteristics.  For homework tonight I
>> want you to QSO with some hams and jot down what you
>> like and don't like about their audio signal. Then ask
>> them what microphone they are using.  We will meet
>> again next week and compare notes.  Maybe we'll all
>> learn something new about microphones. CLASS
>> Just as a Postscript I used to have a bookmark for a
>> company that will take your D-104 and for $125.00 make
>> it sound like a real ham radio microphone. I heard one
>> of them on the air and it sounded sweet.  If I find
>> them again I'll post it.
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