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Re: [Amps] PA efficiency

To: amps@contesting.com
Subject: Re: [Amps] PA efficiency
From: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Wed, 18 May 2011 05:36:40 +0100
List-post: <amps@contesting.com">mailto:amps@contesting.com>
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
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