Yep. Those good 'ol carbon microphones. They even worked when plugged
into the cathode keying circuit of my original Novice transmitter when I
passed the General. The varying resistance of the carbon granules with
about -90 vdc applied modulated the cathode current and produced some bad,
but readable, AM modulation.
Remember the coherer of days long past - think Marconi and the early days
of radio. It consisted of a small volume of iron and metal filings
(hopefully with a little rust and corrosion of varying degrees) that was
constantly shaken by a bell ringer or other means. Kinda like a carbon
microphone.
Dave - WØLEV
On Mon, Feb 24, 2020 at 7:17 PM Jim Brown <jim@audiosystemsgroup.com> wrote:
> On 2/24/2020 7:28 AM, Mike & Becca Krzystyniak wrote:
> > Back then we always heard the programming on the phone lines it worsened
> when it rained.
>
> The carbon mics used in older phones were great RF detectors.
>
> When I lived and worked in Chicago, I knew most of the engineers for the
> local stations. The Chief Engineer of WCFL told me it was a particularly
> tricky one to keep within FCC parameters, because it was a directional
> array composed of towers of different height and construction.
>
> 73, Jim K9YC
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>
--
*Dave - WØLEV*
*Just Let Darwin Work*
*Just Think*
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