[Amps] PA efficiency

[Dr. David Kirkby]

On 05/18/11 05:27 AM, Carey Lockhart, KC5GTT wrote:
> hello all,
>
> what is the proper formula to get the PA efficiency of a amplifier?
>
> Carey

1) Calculate the input power = V * I

where V is anode/collector/drain voltage (depending on whether its tube or 
semiconductor

I is the anode/collector/drain current (depending on whether it's tube or 
semiconductor)

2) Measure the output power P.

3) Efficiency (in percentage) = 100*P/(V*I)


Note, few power meters are going to be accurate to better than +/- 10% 
(including the Bird, despite its spec of 5% of FSD), so don't expect an accurate 
result unless you use a precision power meter with a calibrated coupler or 
attenuator.

Dave