[Elecraft] [OT] Measurement of Power

[Joe Subich, W4TV]

> And by the way, I thought the Bird spec was 5% of full scale. Where 
 > did 20% come from?

The Model 43 is 5% of full scale: 
<https://birdrf.com/Products/Test%20and%20Measurement/Power-Meters/Wattmeters-Line-Sections/RF-Wattmeters/43_General-Purpose-Wattmeter.aspx> 


I still have the Model 43 my wife gave me for Christmas 40 years ago,
along with the ten elements (2 MHz - 2.5 GHz) and eight QC connectors
of various types (UHF, N, BNC, LC) I've accumulated over the years
even though I the microHAM SMΩRF vector wattmeter has replaced my
original Telepost LP-100(A) in day to day use.  Although the "modern"
digital meters are used in the shack, the Model 43 provided years of
faithful service both in the shack and in the field and is still my
"go to" unit outside the shack.

Again, do it once and buy quality he first time.

> ± 20% in Watts, is about ± 1 dB in log. 1 dB accuracy is plenty good 
 > enough for us,

± 5% of full scale is ± 0.22 dB - far more accurate than needed for
amateur and most commercial use (although SMΩRF is NIST traceable and
accurate to ± 0.04 dB or ~1.5%).

73,

    ... Joe, W4TV


On 3/19/2018 4:22 PM, Al Lorona wrote:
> I re-named the thread as a courtesy to the members who don't want to read this.
> 
> We're getting caught in a mathematical war between the linear and logarithmic worlds.
> 
> 
> ± 20% in Watts, is about ± 1 dB in log. 1 dB accuracy is plenty good enough for us, folks. Especially given that any impedance mismatch is a source of error that we typically can't eliminate.
> 
> In addition, I have found that Bird is very conservative and typically beats this spec by a lot. And by the way, I thought the Bird spec was 5% of full scale. Where did 20% come from?
> 
> Don't all rush out to sell your Birds. They're perfectly fine.
> 
> 
> Al  W6LX
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