oops, Alan is right. Brain not engaged. Bob
On Mon, Dec 31, 2012 at 3:41 PM, Alan Bloom <[email protected]> wrote: > Matt, > > -174 dBm is the noise of a resistor at room temperature in a 1 Hz > bandwidth. In a 500 Hz bandwidth (which seems to be the standard for > receiver measurements) you get 10 * log(500) = 27 dB more, or -147 dBm > thermal noise. > > So 35 dB excess noise is -147 + 35 = -112 dBm in a 500 Hz bandwidth. With > a 2.7 kHz SSB filter, it should be -104.7 dBm. > > The KX3 S meter may not be accurate for noise. I expect the AGC tends to > respond to peak signal level rather than RMS. That would give a higher > than expected S meter reading, which is what you observed. > > The way to measure the N-gen output is to turn off the AGC, reduce the > signal level so the audio output is not distorting (using attenuator or > whatever) and measure the audio output with an RMS voltmeter. Then connect > a calibrated signal generator and adjust its output level for the same > meter reading. If you don't have a true RMS voltmeter you'll be off a dB > or two, but it should be in the ballpark. > > Alan N1AL > > > > On 12/31/2012 2:33 PM, Matt Zilmer wrote: > >> Couple of questions on the N-gen: >> >> 1. The instruction sheet gives "35 dB" of Excess Noise Output. Is >> this referenced to -174 dBm or some other? >> >> I'm seeing S0 on a KX3 with the switch OFF, and S5-6 with the switch >> on. Seems usable. I have S5 at -97 dBm, S6 at -91 dBm. So the >> reference level is around -132 to -126 dBm, if I read this spec >> correctly. >> >> 2. Can someone reference a data sheet for the MAR-1 MMIC? I'm going >> to search for it, but thought someone might have it around. >> >> The N-gen makes a nice 30 minute build, and is fun. Parents are still >> giving me kits even though I'm 55 y/o - because they want to watch me >> build them - yes, right on the spot in their living room in Tucson. >> >> I restrained meself until we got back to SoCal and I had my wrist >> strap on. >> >> Happy New Year to All. >> >> 73, >> matt W6NIA >> ______________________________**______________________________**__ >> Elecraft mailing list >> Home: >> http://mailman.qth.net/**mailman/listinfo/elecraft<http://mailman.qth.net/mailman/listinfo/elecraft> >> Help: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm> >> Post: mailto:[email protected].**net <[email protected]> >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> >> >> ______________________________**______________________________**__ > Elecraft mailing list > Home: > http://mailman.qth.net/**mailman/listinfo/elecraft<http://mailman.qth.net/mailman/listinfo/elecraft> > Help: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm> > Post: mailto:[email protected].**net <[email protected]> > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
