-=> On 12-16-97  18:30, Ed Kriston said to All,<=-
-=>"About Telex CS-78 headphones/mi...,"<=-
 
Hi, Ed;
 
 EK> I have become the proud owner of a set of Telex headset.  I would
 EK> surely love  to connect these to my TS-140S Kenwood.  There are no
 EK> markings on the mic to  say what the impedance is.  I figure that there
 EK> might be an impedance mismatch  between the headset and radio.  Anybody
 EK> have any idea what the impedance is on  the microphone?  Will it work
 EK> with my radio?  I have the book for the radio and know that I need to
 EK> have another PTT setup.  BTW, there is also the number  61320-10 on the
 EK> mic mount earpiece.  Any help to get these working would be 
 EK> appreciated.
 
I'm not famililar with that particular model of headset, but a lot of
those "telephone operator" style headsets use a carbon mic.  If it is,
it will work with your radio, however you will need a well-filtered
low-voltage power supply, (2-6 volts is plenty), a small audio
transformer - an output transformer connected "backwards" to step down
will work - and since the AF output of a carbon mic is very high you will
probably need to use a resistive padder to cut the AF down to the level
of a dynamic mic.  Heck, you can connect a carbon mic, a 6V battery and a
speaker in series with no amplifier and use it as a low-powered intercom!
These mics are not high-fidelity by anyone's definition, but they are
quite suitable for comm work, since they work well around 200-3000 Hz,
which is what you want.  Their big drawback is that the carbon granules
tend to get packed and the output drops to near nothing.  If this
happens, a couple of sharp raps on the table will get them going again.
 
 EK> I have a seven year old grandson that is great at
 EK> QRN/QRM while I am operating.
 
Aren't they all?  I think that's called "Harmonic radiation."  ;-]
 
Merry Christmas es Happy New Year to you and yours.
 
N3WJA DE KB9QPM  73
   Ivy
 
 
 
... If wavelength = short, then Megahertz < 30
 
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