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Old February 1st 08, 06:49 AM posted to rec.radio.amateur.antenna
K7ITM K7ITM is offline
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First recorded activity by RadioBanter: Jul 2006
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Default 70cm reflectometer?

On Jan 31, 1:46 pm, Cecil Moore wrote:
K7ITM wrote:
See earlier posting in this thread.


Thanks Tom, when I said "linear power scale", I meant
e.g. a meter reading where 2000 watts is full scale
and 1000 watts is half scale. I have seen such meters
but not without a digital or analog computer on the
front end.
--
73, Cecil http://www.w5dxp.com


Right, and I'm saying that with a coupler or sampler that picks off,
say, 1e-7 of the power (0.2 milliwatts of RF out for 2000 watts in/
through), a diode detector that shows that power to be full scale on a
linear meter will show 1000 watts at half scale. That assumes that
0.2 milliwatts is low enough to get you into the square law region of
the detector; for an HSMS-2850 diode, that's a bit high. Because the
power at which the square law holds accurately is so low (and the
detector output is so low) you need an electronic way to read that
output; a simple meter movement isn't likely to do the trick. But
there's no need for any fancy processing.