[ARC5] [Milsurplus] Audio Impedance Matching on USAAF aircraft

[Al Klase]

Silicon Carbide was know as carborundum.  It was not near as good a 
detector as galena, but was far more stable.
Marconi America provided both in their marine receivers such as the 101, 
but claimed their galena was cerussite, a total lie.
See: https://skywaves.ar88.net/xtal/Cerusite/
A 2000 Ohm (DC) headset was appropriate for either.

73,
AL

On 12/31/2025 8:39 PM, Jim Haynes wrote:
>
> Some old detectors used a bilateral substance such as SiC.  A battery 
> can shift the operating point away
>
> from the center to a place where the material is nonlinear and able to 
> rectify.
>
> -----Original Message-----
> From: 1oldlens1 <1oldlens1 at ix.netcom.com>
> Sent: Dec 31, 2025 1:09 AM
> To: Hubert Miller <Kargo_cult at msn.com>, ARC5 <arc5 at mailman.qth.net>, 
> List Milsurplus <milsurplus at mailman.qth.net>
> Subject: Re: [ARC5] [Milsurplus] Audio Impedance Matching on USAAF 
> aircraft
>
> Many very old diagrams for crystal detectors show a battery buying 
> never used one on the crystal sets I built as a kid and don't fully 
> understand  why they were used
> I've found exactly one Brusg headphone that worked,  the others just 
> had mush inside. Brush held the patents for crystal microphones, 
> headphones, phono pick ups and cutters. Licensed many other companies. 
> But others seemed to have better sealing and protection. Unlike 
> magnetic and dynamic phones, which are usually in series, crystal 
> phones are in parallel.
> Sent from my Galaxy
> Richard Knoppow
> Los Angeles
> WB6KBL
> -------- Original message --------
> From: Hubert Miller <Kargo_cult at msn.com>
> Date: 12/30/25 10:41 PM (GMT-08:00)
> To: ARC5 <arc5 at mailman.qth.net>, List Milsurplus 
> <milsurplus at mailman.qth.net>
> Subject: Re: [ARC5] [Milsurplus] Audio Impedance Matching on USAAF 
> aircraft
>
> ‘Crystal’, piezo earphones, actually went to 100kR, but thanks to 
> Brush Co. lack of type markings, good luck separating these from 50kR 
> ones.
>
> There is no way just looking at them. I find the Brush phones, about 
> 50% are now defective. I have a magazine article on how to “grow” your own
>
> crystal for headphone use, but that’s something on the back burner for 
> forseeable future.
>
> I noticed recently that the little earpieces that came with ‘Rocket 
> Radios’ and other Japanese import crystal radios 1960s – 1980s, have been
>
> “improved” with brass diaphrams. Whereas with the old ones, you look 
> down into them, and you see an aluminum colored diaphram. The
>
> “new improved” ones are noticeably less effective, altho maybe more 
> rugged. Good crystal phones, you squeeze one lead in one hand, hold the
>
> other contact to a wall AC switch screw, with the switch in ‘ON’ 
> position, you should hear a moderate strong hum.
>
> Did you know ? A ‘crystal radio’ with a piezo earphone, does NOT need 
> a DC circuit from diode to headphone. An AC circuit, with a cap like
>
> 10nF, will do.
>
> -Hue Miller
>
>
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-- 
ARK Sig Block Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/

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