Fw: Re: [Test-Equipment] Spectrum Analyzer BW measurement

[windy10605@juno.com]

Thanks, Dave. That answers some of the questions as to why 3Khz.
 
>        Your RC remote control spec seems have used the later form -
>specifying how many db down from the carrier level the noise power
>reading in a 3 khz RBW centered 20 khz from the carrier is supposed to
>be.   This obviously is trivial to measure correctly if you have a
>spectrum analyzer with a 3 khz bandwidth, but a little more complex if
>you have one (as you do with only 500 hz and 5 khz bandwidth).

Right, and what is the "little more complex" proceedure ? Other than my 
"rough estimate" indicated in a previous note.

>        In fact most (or at least many) digital (and for that matter
>analog)  signals have a nose or hump that contains most all the energy.
>The width of this can be most accurately viewed with a narrow resolution
>bandwidth relative to the width of the signal (few percent).

There are actually two specifications. One is the FCC spec for R/C
transmitters
which specs BWs at -25dB, -45dB, -55dB, and peak detect (based on the
+/-10Khz BW spec at -55dB a RBW/BW ratio of a few percent is implied). 
Of the 5 RBWs I have, 500Hz RBW fits best and I have no problems with 
those measurements. 

The other is an AMA spec for -55dB for (apparently +/-) 20Khz using 
3Khz RBW. That's the one I have problems with ....correlation to my 
measurements using 5Khz RBW or correlation to the FCC spec. 

73 Kees K5BCQ