[Milsurplus] Aw Heck (Was: SIMPLE Carbon Microphone Sub)

[Richard]

Well, it must be that it is not linear.  At microamperes it's 20 k Ohms, 
and at milliamperes it's a few hundred Ohms.  This is no surprise.  I am 
following your researches with great interest.

Richard, AA1P

On 05/29/2016 09:50 PM, David Stinson wrote:
> (I'm copying this to milsurplus only because it's
> the only place anyone responds so I assume these are the only people 
> who read.)
>
> Ya'll remember me telling you about this "magic" T-17
> being stock?  I had to know so I unsealed the screws.
> It was black wax instead of the usual stuff, which gave
> me an "uh oh" feeling right there.
> I opened it and... It ain't stock.
> Inside is an N-1 telephone element.
> Glued to the microphone face.
> And some stuffing.
>
> Well... I did some research and found out exactly who did this.  I 
> nailed that evil-doer!
> It was me.  In 2012.
> Guys, I have NO MEMORY at all of doing this.
> None.  Not a shred.  Yet there I am on qrz.com
> in October of 2012 talking all about it.
> Which wasn't that long ago.
> Diabetes can cause early-onset dementia.
> Frightening.   But at least that part of the "magical mystery T-17" is 
> solved.
> HOWEVER, the other mysteries remain.
>
> I've checked this "magic" N-1 with my Fluke 8050A
> bench meter and my brand new Fluke 77 hand meter.
> Assuming I remember how to read them....
> On both meters, it checks about 20K Ohms.
> And it works spendidly on most of my mil-rigs.
> I have another N-1, a T-1 and other various elements.
> All read 60-300 Ohms.  None will modulate
> any of the rigs properly.  The best of this lot
> is the large K1 transmitter element in the "candle stick"
> microphone.  It measures 2K Ohms and will mod the rigs about half way 
> if you yell.
> I see all your information.  I don't take issue with it.
> I don't understand why this is happening.
> It just is.
>
> A dim light came on in what passes for my brain.
> Take another look at the electret carbon mic
> replacement circuit:  https://goo.gl/photos/26HUmzVuqhZKWrNZ7
>
> This puts out nice-sounding audio and will modulate
> the rigs fully, but you got to close-talk it.
> I haven't tried another electret- looking for a higher-
> gain transistor first.  2N2222 is a little better.
>
> The circuit.... and a 2K carbon element...hmmm.
> So I did this:
> https://goo.gl/photos/6Ua2hJmLdSrkigw57
>
> And "Ala-Kazam!" I got excellent-sounding,
> 100% modulation from a normal voice using
> this very cool "candle-stick" mike.
> Fortunately, the element in this mike
> is isolated from ground.
> And one less part, so "The Law of Pernicious Parts Count" is being 
> respected.
> Put a little board right on the back of the
> element and away we go.
> https://goo.gl/photos/Ce4RQuJGBY3WciBK9
>
> Just to be through, I did try the Lo-Z elements
> ( Hey... Z=X+R, even when X is zero).
> and they did not work, as we would expect since
> they don't bias the transistor properly
> and if you put them in series with a resistor,
> they aren't a big-enough fraction of the total
> Z to matter.
> I'm thinking of a proper bias divider and putting the Lo-Z elements in 
> the Emitter lead.
> More than one way to skin a cat!
>
> Will let you know if that works.  In the mean time,
> can someone tell me why an N-1 element that
> measures 20K Ohms works so well??
>
> 73 DE Dave AB5S
>
>
>
>
>
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