[Boatanchors] Carbon Mic Rejuvenation (& related)

[jmfranke]

The carbon microphone was used with a transformer having a high turns ratio 
as an amplifier and oscillator. In such a configuration, gain was achieved. 
The amplifiers were used as early telephone line amplifiers and as 
amplifiers for crystal radios. General radio used carbon mike amplifiers in 
its microphone hummers and many models of tuning fork oscillators. Some 
texts referred to microphone amplifiers as relay amplifiers.

John  WA4WDL

--------------------------------------------------
From: "rbethman" <rbethman at comcast.net>
Sent: Saturday, March 16, 2013 4:16 PM
To: <boatanchors at mailman.qth.net>
Subject: Re: [Boatanchors] Carbon Mic Rejuvenation (& related)

> Mac, (or Dennis whichever you prefer...)
>
> I think you have hit the exact description!
>
> The rest of the conversation was essentially theoretical, in lieu of 
> actual.
>
> Bob - N0DGN
>
>
> On 3/16/2013 3:51 PM, mac wrote:
>> Bill is correct about passive elements and power gain.  Perhaps some of 
>> the confusion here centers around consideration of a carbon microphone as 
>> a "passive element." Standing alone it certainly is, just as a vacuum 
>> tube with no filament or B+ applied would be passive.  Put the tube in a 
>> practical circuit though, i.e., power source and a load impedance and it 
>> becomes the "active " element we usually consider it to be.  So, would a 
>> carbon mic augmented with a load impedance and bias (power) supply now 
>> (properly) be considered an "active" element?  Different from a crystal 
>> or dynamic mic neither of which require a bias (power) source to operate. 
>> Academic question but interesting.....
>>
>> Dennis D.  W7QHO
>> Glendale, CA
>
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