[AMRadio] mike


StephenTetorka at cs.com StephenTetorka at cs.com
Tue Mar 15 12:30:47 EST 2005


I appreciate all your time and help, guys.

Excuse me for not mentioning the cathode resistor for bias.

>From what little I have found...both the Collins 310A exciter and WRL Globe King 275 use a 6SJ7 for mike input...in which case, a hi-Z dynamic should work.

So...back to square #1 - what is "hi"?

Mouser has cheap ( $4 ) crystal elements whose impedance range is from 9K to 25K which doesn't look "hi" to me.

I've also read that a ceramic element - acting in the same fashion as the piezoelectric - can be used.
Which means that my Electro-Voice 729 is a candidate which is already on my shelf...sparkling since I polished all that cast metal to high sheen.

The modulators are 2 x 807's going into an RF deck of 2 X 1625's having link coupled input from a 6L6 oscillator or 6L6 doubler stages...fortunately, I can get the 3.5715 Mc FT 243 type rock from PR Crystal for my 20 meter AM freq 14.286...only $15.

Working on this restoration is a great learning experience for me...and again, I sincerely appreciate you sharing with this rookie.

Regards,
Steve
WA2TAK

PS...the 813 homebrew restoration is in the workshop patiently waiting for me...another 1x3 - now SK - in North Carolina made it.



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