[TenTec] Mics in general
JEFF S JOHNSON
aa8ve@juno.com
Fri, 1 Oct 1999 14:38:36 -0400
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>
writes:
>
> 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
> DISMISSED!
>
> 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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