Of course you do Jeff but you also need to know how much power is passing
thru.
With tubes that include the required drive power on the spec sheet its easy
to do. With Ruskie tubes you may need to take a WAG if the data isnt
published.
Carl
KM1H
----- Original Message -----
From: "Jeff Blaine" <keepwalking188@yahoo.com>
To: "Dr. David Kirkby" <david.kirkby@onetel.net>; <amps@contesting.com>
Sent: Wednesday, May 18, 2011 1:33 AM
Subject: Re: [Amps] PA efficiency
David,
In the case of the GG, do you not need to deduct the drive power from the
Po? Otherwise, the efficiency is overstated and the Pd is
understated. I could be wrong?
73, Jeff ACØC
www.ac0c.com
-----Original Message-----
From: Dr. David Kirkby
Sent: Tuesday, May 17, 2011 11:36 PM
To: amps@contesting.com
Subject: Re: [Amps] PA efficiency
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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