[JMS] 250 Watt modulator for 90881

[JAMES HANLON]

Cal,

You could figure out the primary-to secondary turns ratio of your modulation transformer with a simple measurement.  Drive one side with an audio oscillator or other audio signal, say the output from your receiver, and measure the voltage on both sides of the transformer.  The turns ratio is just the ratio of the two voltages.  The impedance ratio from one side of the transformer to the other is the square of that turns ratio.  You can look up in the ARRL handbook the impedance for a pair of 811's in Class B, and knowing the impedance ratio from your measurement and calculation you can determine what the design impedance for the other side of the transformer is.

Does that make sense?

Jim, W8KGI