[ARC5] Make that Old T-17 Work with BC-456

Thu Apr 2 16:37:29 EDT 2020

I apologize!

I didn’t notice that the thread was about the BC 456!  I would imagine it would not work well with that.  I do use it with many aircraft radios that have a carbon equivalent input, however, and yes, 100-200 mV is about what it delivers, I caution that it must be a three terminal electret with the low impedance follower output, though.

Scott V. Johnson W7SVJ

5111 E. Sharon Dr.

Scottsdale, AZ 85254-3636

H (602) 953-5779

C (480) 550-2358

 <mailto:scottjohnson1 at cox.net> scottjohnson1 at cox.net

 <mailto:scott.johnson at ieee.org> scott.johnson at ieee.org

From: J Mcvey <ac2eu at yahoo.com> 
Sent: Thursday, April 2, 2020 12:17 PM
To: 'Doran Platt' <jeepp2 at comcast.net>; arc5 at ix.netcom.com; arc5 at mailman.qth.net; Scott Johnson <scottjohnson1 at cox.net>
Subject: Re: [ARC5] Make that Old T-17 Work with BC-456

An electret doesn't develop enough output to drive the modulator .. You only get 100 to 200 mv out 

You need current and voltage  amplification to drive the the lo-z input.

I made these a few years ago. it will provide more that sufficient drive for 100% modulation.

www.mcveyelectronics.com/military-radio/t-17-lollypop-microphone-cartridge-replacement-prototype <https://www.mcveyelectronics.com/military-radio/t-17-lollypop-microphone-cartridge-replacement-prototype> 

McVey Electronics - Small drop-in PCB replacement for the carbon microph...

Jim McVey

Most of the T-17 mkes used inn WWII radio have poor or defective carbon cartridges, resulting in poor or no modu...

An electret doesn't develop enough output to drive the modulator .. You only get 100 to 200 mv out 

You need current amplification to drive the the lo-z input.

I made these a few years ago. it will provide more that sufficient drive for 100% moodulation.

On Thursday, April 2, 2020, 2:48:37 PM EDT, Scott Johnson <scottjohnson1 at cox.net <mailto:scottjohnson1 at cox.net> > wrote: 

There are plenty of electret capsules out there that have a follower off the FET preamp that will drive a carbon input. I have had good luck with the three terminal capsules I have salvaged from computer mics, Sometimes a voltage dropping network is needed prevent overvoltage (DC) to the element.  Most are limited to 5-8 VDC.

Scott V. Johnson W7SVJ

5111 E. Sharon Dr.

Scottsdale, AZ 85254-3636

H (602) 953-5779

C (480) 550-2358

 <mailto:scottjohnson1 at cox.net> scottjohnson1 at cox.net

 <mailto:scott.johnson at ieee.org> scott.johnson at ieee.org

From: Doran Platt <jeepp2 at comcast.net <mailto:jeepp2 at comcast.net> > 
Sent: None
To: scottjohnson1 at cox.net <mailto:scottjohnson1 at cox.net> ; arc5 at ix.netcom.com <mailto:arc5 at ix.netcom.com> ; arc5 at mailman.qth.net <mailto:arc5 at mailman.qth.net> 
Subject: Re: [ARC5] Make that Old T-17 Work with BC-456

I believe electret/carbon compatible mics all have an appropriate amplifier associated with it.
K3HVG Jeep

Sent from Xfinity Connect Application

-----Original Message-----

From: scottjohnson1 at cox.net <mailto:scottjohnson1 at cox.net> 
To: arc5 at ix.netcom.com <mailto:arc5 at ix.netcom.com> , arc5 at mailman.qth.net <mailto:arc5 at mailman.qth.net> 
Sent: 2020-04-02 2:15:09 PM 
Subject: Re: [ARC5] Make that Old T-17 Work with BC-456

Why not just install a 50 cent electret cartridge in the T-17, and call it a day?  (you’ll have the finest sounding T-17 around!)

Scott V. Johnson W7SVJ

5111 E. Sharon Dr.

Scottsdale, AZ 85254-3636

H (602) 953-5779

C (480) 550-2358

 <mailto:scottjohnson1 at cox.net> scottjohnson1 at cox.net

 <mailto:scott.johnson at ieee.org> scott.johnson at ieee.org

From:  <mailto:arc5-bounces at mailman.qth.net> arc5-bounces at mailman.qth.net < <mailto:arc5-bounces at mailman.qth.net> arc5-bounces at mailman.qth.net> On Behalf Of David Stinson
Sent: Thursday, April 2, 2020 11:00 AM
To: ARC-5 < <mailto:arc5 at mailman.qth.net> arc5 at mailman.qth.net>
Subject: [ARC5] Make that Old T-17 Work with BC-456

Got a BC-456 modulator you want to use, but only "dud" T-17 mikes?  Yes; in a perfect world, we'd wait and search until we found a "good" T-17.   This world ain't perfect.  I don't know about you, but the sand in my hour glass is getting a little low, and given the current world situation,  I'd kinda like to enjoy my gear before "Ol' Grim" comes to collect me.  

So if you're T-17 will so even 10% mod, here's a non-destructive way to change two resistors and get your BC-456 modulator singing for you:

 <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=icon> 

Virus-free.  <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=link> www.avast.com 

______________________________________________________________ ARC5 mailing list Home:  <http://mailman.qth.net/mailman/listinfo/arc5> http://mailman.qth.net/mailman/listinfo/arc5 Help:  <http://mailman.qth.net/mmfaq.htm> http://mailman.qth.net/mmfaq.htm Post:  <mailto:ARC5 at mailman.qth.net> mailto:ARC5 at mailman.qth.net This list hosted by:  <http://www.qsl.net> http://www.qsl.net Please help support this email list:  <https://www.qsl.net/donate.html> https://www.qsl.net/donate.html

______________________________________________________________
ARC5 mailing list
Home: http://mailman.qth.net/mailman/listinfo/arc5
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:ARC5 at mailman.qth.net <mailto:ARC5 at mailman.qth.net> 

This list hosted by: http://www.qsl.net
Please help support this email list: https://www.qsl.net/donate.html

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/arc5/attachments/20200402/da135c2f/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image003.jpg
Type: image/jpeg
Size: 9371 bytes
Desc: not available
URL: <http://mailman.qth.net/pipermail/arc5/attachments/20200402/da135c2f/attachment-0001.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image004.png
Type: image/png
Size: 1881 bytes
Desc: not available
URL: <http://mailman.qth.net/pipermail/arc5/attachments/20200402/da135c2f/attachment-0001.png>