[ARC5] Reverse engineering the BC 456 - carbon microphones

[Dave Jackson]

Mike:

 

No idea on the transformer

 

The 82 ohm resistor looks to me to provide a known load for the microphone current source in order to measure the available current.

 

Dave, WA4OBJ

 

From: ARC5 [mailto:arc5-bounces at mailman.qth.net] On Behalf Of MICHAEL ST ANGELO
Sent: Tuesday, March 21, 2017 1:29 PM
To: kn7sfz; arc5 at mailman.qth.net
Subject: Re: [ARC5] Reverse engineeing the BC 456 - carbon microphones

 

Nice unit.

 

Does anyone know the output impedance of the matching transformer. What is the purpose of the series 82 ohm resistor in the output?

 

Mike N2MS

 

 

 

On March 20, 2017 at 12:27 AM kn7sfz <kn7sfz at gmail.com> wrote:

Ah, thanks for the nomenclature.  I see there's a pic of one from last year on UK EBay including a small schematic.

Neato!

http://www.ebay.co.uk/itm/Mikrofon-Simulator-SM-30-URM-14-U-S-Property-/161665642681?nma=true <http://www.ebay.co.uk/itm/Mikrofon-Simulator-SM-30-URM-14-U-S-Property-/161665642681?nma=true&si=sOZryufJjssBAY1p1jrnK9Y3Rk8%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557> &si=sOZryufJjssBAY1p1jrnK9Y3Rk8%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557


Richard kn7sfz





On 3/19/2017 9:11 PM, WA5CAB--- via ARC5 wrote:

Would that be the SM-30/URM-14?  Handy gadget.  I turned one of them into a carbon microphone tester, complete with bias battery.  The unmodified unit sits between an audio oscillator and the transmitter carbon mic jack.  Has a handy switch across the key line.  And a built-in meter.  I have a reprint of the 6-page manual on it available.

In a message dated 03/19/2017 19:08:02 PM Central Daylight Time, kn7sfz at gmail.com writes: 



Picture?

I'd like to say I've seen one before I pass on......:-)

Tnx Wayne,

Richard kn7sfz


On 3/19/2017 4:58 PM, Robert Eleazer wrote:




By the way, should anyone need one, I have a piece of test equipment called a "Microphone Simulator."  I have no idea what it does or why it does it..

Wayne
WB5WSV 

 



Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480 

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