[TowerTalk] Bird ratings

[Tom Rauch]

> OUTPUT = 1150-1200 watts
> REFLECTED = 250-300 watts
> DIFFERENCE = 900 watts
> BIRD ERROR =  +/- 5% or 50 watts @ 1000 watts
> ACTUAL POWER ANTENNA & FEEDLINE "ACCEPTS" = 850-950 watts
> HENRY OUTPUT = 1000 watts continuous, ON or OFF, with the Palstar
> keeping output even by matching whatever it "saw" on the line to the 50
> ohm output requirements of the Henry.
> 
> Somewhere between 50 and 150 watts of the RF that the Henry shipped out
> though the Palstar tuner was eventually lost in the coax or tuner?

The accuracy of a calibrated in-spec Bird is + or - 5% of the full 
scale reading ***anywhere on the scale***. 

That's why you should never use a high power slug to read low 
power levels, including reflected power readings.

The most accurate way to measure loss in a tuner with different 
source and load impedances is to measure the temperature rise in 
the tuner, not the power levels. 

If the input Zo and output Zo are 50 ohms j0, you could move the 
SAME meter from input to output and the reading would be 
accurate, but you should never use two different meters and/or 
slugs unless they are calibrated against each other. In this case, 
the absolute reading would not matter as long as the meters 
tracked each other. Then you could determine efficiency and it 
would be pretty accurate.

You'd be amazed how many sets of data are published where 
accuracy is only +-3 dB (or something worse) and the answer is 
expressed in tenths of a dB!


  

73, Tom W8JI
w8ji@contesting.com

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