Bias and Gate Voltage Question

[KD8HMO]

I have a question about the transmit alignment procedures for the RCI 2970N2 and the Galaxy 98VHP. Assuming the amp boards are the same, Why does ranger recommend setting the gate voltage at 3.5v with 100w deadkey, and Galaxy says 4.0v at 65w deadkey? How much of a difference does .5v make with those 520's? Also, It seems that most of these radios with MOSFET finals usually spec 3.8v on the driver bias, and 3.5v on the final bias. I just bought a brand new DX-959 "Deluxe" with the blue display and meter, and it had both driver and final bias set to 4.2v from the factory, with two watt dead key. Could these higher settings be correct in this new radio?

 

[Tallman]

Never assume with power amplifier voltages. Analyze both of the amplifier circuits and make an informed decision. Or call the Galaxy technical customer service help line. I'm sure that they have dealt with all of the possible permutations you can imagine. In any case they can tell you the proper settings.

 

[543_Dallas]

I'd just follow the manual for the radio you're working on. Have you checked the bias voltage at 65 watts and then at 100? Unless the circuit is well regulated it may change. Two different methods to get the same result.

 

[loosecannon]

or set your bias using a scope and then come back and tell us what gate voltages you ended up with.
LC