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#3
May 1st 06, 09:14 PM
posted to rec.radio.amateur.antenna
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spectral power density
dBm = watts = 0.001 watt as a reference
K7ITM wrote: I'm not going to bother trying to look it up--but is that not supposed to be something like 8dBm/3kHz BW, or some such? 8dB without a reference doesn't mean much. If it's 8dBm/3kHz, then the meaning should be obvious: in any 3kHz band there may not be more than +8dBm power (I guess around 7 milliwatts). Spectral density is commonly measured with a spectrum analyzer; many modern ones have band markers that will let the instrument perform a band power measurement. If you spread 1 watt uniformly over 500kHz, you'd have 1W*3kHz/500kHz, or 6mW, in each 3kHz bandwidth. So the +8dBm limit would mean that the power should be spread very nearly uniformly over that band. (Why did they use units of watts in one place and dBm in another??) Cheers, Tom |
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