[ARC5] Driving the BC-456

[David Stinson]

Good stuff!
Please keep us posted with details of your progress.
73 Dave AB5S

----- Original Message ----- 
From: "J Mcvey via ARC5" <arc5 at mailman.qth.net>
Subject: [ARC5] Driving the BC-456


>I was noodling with the electret mike circuit today.It turns out 
>that the initial reverse engineering results were pretty 
>close.The input Z is very low, in the 30-50 ohm range. 4Vpp DOES 
>NOT overdrive the modulator!This falls in the T-17 mike spec 
>which was a max of 1.7 Vrms ( 4Vpp = 1.41Vrms)
> It looks to be about 80% modulation@ 4Vpp.
> I thought that would be enough , but it looks like it would be 
> good to have more adjustable range to5Vpp or 6Vpp.
> The internal tone modulation looks like 100%+
> So far, the circuit consists of two active devices. A LM3900 
> and MPSA06 npn transistor.A LT1006 or equivalent would probably 
> work as well-maybe better, but I have the LM3900's on hand.
>