[Milsurplus] SIMPLE Carbon Microphone Substitute.

[WA5CAB at cs.com]

I'm afraid that I must also agree.  The only way you would find a T-17 with 
20K ohms DC resistance would be if the element was totally bad or the PTT 
switch contacts weren't working.

In a message dated 05/28/2016 18:36:04 PM Central Daylight Time, 
hwhall at compuserve.com writes: 
> That's interesting about the T-17 series resistance, because when I was 
> doing some research into carbon button alternatives, I couldn't find any 
> data on T-17 buttons other than "low impedence." 
> 
> Some of the telephone-type carbon buttons I found available ranged from 40 
> to 60 ohms resistance according to maker's data. I thought that T-17 
> buttons would also have to be fairly low resistance since (from the little I 
> understand of them) the carbon buttons controlled current flow (essentially a 
> variable resistor). ARRL Handbooks indicated "the usual" button currents 
> were 50 - 100 mA. Getting 50mA thru 20Kohms would require a whopping lot more 
> than the 4 - 6 volts the old Handbooks showed for running carbon mikes.
> 
> What am I missing??
> 
> Wayne
> WB4OGM
> 
> -----Original Message-----
> From: David Stinson <arc5 at ix.netcom.com>
> To: COURYHOUSE <COURYHOUSE at aol.com>; kgordon2006 <kgordon2006 at frontier.com>
> 
> Cc: milsurplus <milsurplus at mailman.qth.net>
> Sent: Sat, May 28, 2016 11:48 am
> Subject: Re: [Milsurplus] SIMPLE Carbon Microphone Substitute.
> 
> 
> ----- Original Message ----- 
> From: <COURYHOUSE at aol.com>
> Subject: Re: [Milsurplus] SIMPLE Carbon Microphone Substitute.
> 
> 
> >ah... what about a carbon microphone element from an old 
> >telephone
> >handset?
> 
> Too lo-Z for the BC-669. I've looked at lots of Carbon mike
> elements and they come in various impedances.
> The series resistance of the best T-17 I have is over
> 20K Ohms. Telephone mics are usually around 500 ohms.
> Some are as low as 200. That works OK with some rigs,
> like the "ARC-5" sets,. but not well with the 669 or TCS.
> 
> 73 Dave S.
> 

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/milsurplus/attachments/20160529/e622f73b/attachment-0001.html>