Jim, I know perception is 99% of reality, but your measurement technique is not entirely valid. The proper way to make the determination of sensitivity is to measure the MDS of each of the receivers. Use your XG1 signal generator to determine the MDS of each reciever using the technique outlined in the XG1 manual.
A more sensitive receiver will create more "antenna noise" than one that is less sensitive. Say that the K3 can hear a -138 dBm signal, and the atmospheric noise is -136 dBm, then the K3 will hear all signals on that band that are greater than that -136 dBm noise level. If the MDS of the other receivers is at -132 dBm, they will not be able to hear the atmospheric noise, and will also not be able to hear a signal of -133 dBm either. A receiver that hears more 'antenna noise' is usually the more sensitive one. The noise floor - the noise level with the antenna disconnected - is the limit where the receiver will mask weak signals. OTOH, atmospheric noise (antenna noise) will mask signals on all receivers. 73, Don W3FPR Jim HaRRIS wrote: > Tom, > > I have three radio's in my shack besides the K3. I've checked their > S-meters with the recommended XG1 and all have comparable readings. All > four are equally quiet without an antenna connected and with a dummy load > connected. When connected to an antenna the K3 has about 2 S units more > noise indicated than the other radios connected to the same antenna (A/B > switch) and the noise level sounds about that much louder. All volume > controls are at about 9 o'clock. This applies to most bands. Strangely, > WARC bands seem to be mostly excepted. > > This afternoon I took the my K3, K2 and FT-857D mobile using a 54" Li'l > Tarheel II screwdriver antenna tuned to 20 meters. I operated the K3 & K2 > from a SLA battery with the van turned off. I was in a park with nothing > electrical for at least a half mile. Volume was again set at 9 0'clock on > all three. The K3 have a steady S1 with peaks to S3. The other radios had > S0 with no peaks. Volumes sounded appropriate for indicated S-meter > reading. > > I've almost completely disassembled the radio and reassembled it and done > the EE INIT reset with no change. > > It's apparent this K3 is more sensitive to antenna noise than the other four > radio's which are all about equal. This leads me to believe this particular > radio is going to bury weak signals in noise making them harder to dig out > than the other radios. > > I've exchanged several emails with support and next week I'm supposed to > talk with someone higher up at Aptos. I'm trying to be patient with this > but it has been over a month since I placed the initial order. During > assembly I had to replace the DSP board for an unrelated problem. If the > radio has to go back to Aptos it will be close to two months since ordering > before I have a fully functional radio. > > Have a good day and 73, > > Jim, W0EM > > ______________________________________________________________ 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
