On 8/21/2015 9:03 PM, Ken Kopp - K0PP wrote:
Bird accuracy is specified to be ± 5% of meter full scale ... a 100W element would be a poor choice to measure a 100W output level. Take a look at any Bird's meter scale. It's not linear and can be read with the most accuracy to the left of center scale. A 250W element is much better for measuring 100W.
I've a few wattmeters myself, of various makes and accuracy -- no Birds --but if I want ACCURACY I use 40dB directional couplers with additional attenuation into a spectrum analyzer or a 'scope. I generally leave a scope and counter on line for the two main radios in use, with two directional couplers feeding a 2-way hybrid, which lets me monitor power, flat-topping and frequency all at once. Still need to get the GPS disciplined oscillator running, and as I get my brain back (don't ask) I'll get that done.
Note on 'scopes: If all you need one for is setting output safely below distortion level, you don't need $$; the cracked-graticule 15 MHz, flea-market, Leader scope I left at the Lowell (MI) ARC station is good enough reading across a Cantenna.
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