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

Thu Apr 2 15:16:40 EDT 2020

 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

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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...
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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> 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

scottjohnson1 at cox.net

scott.johnson at ieee.org

From: Doran Platt <jeepp2 at comcast.net> 
Sent: None
To: scottjohnson1 at cox.net; arc5 at ix.netcom.com; 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
To: arc5 at ix.netcom.com, 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

scottjohnson1 at cox.net

scott.johnson at ieee.org

From: 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 <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:

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