[ARC5] Reverse engineeing the BC 456 - carbon microphones

[MICHAEL ST ANGELO]

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&si=sOZryufJjssBAY1p1jrnK9Y3Rk8%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557 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
> 
> 
>     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 mailto: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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> >     > 


 

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