Typical KX3 MDS with preamp on is about -138 to -140 dBm in a 500-Hz bandwidth, on all bands.
If a KX3 is measuring -134 dBm MDS in this bandwidth, chances are there's a measurement error, or the ATU has been left in-line at an impedance other than that of the source RF generator, etc. 73, Wayne N6KR On Jul 9, 2013, at 9:15 AM, Edward R Cole <kl...@acsalaska.net> wrote: > To respond to Scott's comment: > > My experience is that the K3 with internal preamp (PRE on) is not able to > hear weak signals as well as the KX3 (with its preamp set to 30-dB gain). > This is an accepted condition by Elecraft and they responded by providing the > PR6 and now expanded this to 10-12m with the PR6-10. > > I suspect (but have no technical evidence) that maybe the K3 is too low in > overall system gain at 6m. The PR6 or other external preamps provide this > (plus lowering system NF). > > MDS is good alternative to noise figure (NF) measurements. The PR6 is cited > by Elecraft providing -143 dBm sensitivity at bw=500 Hz. NF claim is 0.7 dB > with 0.5 typical; PR6 gain = 18 dB. > > The K3 is cited at MDS of -136 dBm at bw=500 Hz. This is adequate > information for calculating equivalent NF. -136 dBm is equivalent to a NF > =11 dB at bw =500 Hz into a 290K termination. Adding the PR6 brings this > down to -145.6 dBm. Pretty close to what Elecraft claims. > > My measurements were with bw=2.8 KHz (-130 dBm), so correcting for bw: > 10Log(2.8/0.5) = 7.5 dB this would result in -137.5 dBm MDS. Considering I > am doing this by ear it comes pretty close to the Elecraft spec for the K3 > with internal preamp. What was a surprise is the KX3 observed MDS was 3-dB > worse than the K3 at -127 dBm (-134.5 dBm corrected for bw). > > My measurements do not match on-air experience?? Only conclusion is that the > test set up is not providing a stable output. XG3 is a great tool for > checking performance but maybe sensitive to loading (just guessing). > Probably the best I can achieve with equipment at hand. Hope the math was > entertaining - HI. > > 73, Ed - KL7UW > > > --------------------------------- > From: Scott Manthe <scott.man...@gmail.com> > To: elecraft@mailman.qth.net > Subject: Re: [Elecraft] K3 6/10M pre-amp > Message-ID: <51db39ce.6080...@gmail.com> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > Maybe the signals are louder on the KX3, which would fool people into > thinking it was more sensitive? I've always thought my K3 was adequate > on 6 meters. Not gangbusters, but certainly adequate. > > 73, > Scott, N9AA > > > 73, Ed - KL7UW > http://www.kl7uw.com > dubus...@gmail.com > "Kits made by KL7UW" > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
