Coil

[Stu Lyon]

I don't think that is enough coil. But it depends on the output impedance of
the tubes.

Assuming a pair of 6146's with 750 volts on the plate, 250 mA plate current
and operating class C -- the Zout would be 1500 ohms**. According to my 1978
ARRL Handbook, pg 159,  7.1 MHz  would require 190 pf on the tube side, 3.14
mHy coil and 942 pf loading cap. My ARRL Lightning Calculator says that 3.14
mHy on a 3" dia / 6 TPI coil would require 5 to 6 turns. Less plate current
or higher plate voltage would raise the Zout and require more inductance. I
would go with 7 turns.

73, Stu W6CUX
Winnetka, CA
W6CUX at earthlink.net

** Zout = (plate voltage)/( 2x plate current in mA)



----- Original Message -----
From: "w0akg1" <w0akg1 at EARTHLINK.NET>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Sunday, December 12, 2004 6:04 AM
Subject: Coil


I've had two answers- one was 3 turns of the 3" dia- 6 turns per inch coil
in parralell with one half of the 437 dual var . For 7.1mhz.  Question is-
leave the dual 225 on the plate side of the coil  as is? and the coil is the
coil in a pi network with the dual 437 to grond. Sound Right? Thanks
Martin Tippin WØAKG
31 Circle Dr.
Windsor, Mo 65360

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