John, Where did you make your measurements? There are significant differences among the line, speaker and headphone outputs as well as the IMD/harmonic performance depending on the level of modification.
73, ... Joe, W4TV > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of John Lemay > Sent: Sunday, December 20, 2009 11:33 AM > To: 'Sverre Holm (LA3ZA)'; [email protected] > Subject: Re: [Elecraft] [K3] K3 Receiver Noise Level -- > Evaluation andAdjustment > > > Hello Sverre > > Thanks for putting your spectral analysis on the web page. > It's very interesting and I decided to do my own test. I used > Spectrum Laboratory, but it displays similar information to Spectran. > > I have deviated from white or pink noise, because most of the > time we are listening to real signals (or qrm!). I decided to > inject a signal: I used my K3 and XG1 to perform the test. > The line out from the K3 was connected to line in on my PC. > > With reference to a fundamental audio signal at 0db, a third > harmonic of this was observed at about -40, and a fifth > harmonic at around -50dB. The even order harmonics are well > down in comparison. > > I don't know if this is a good result or bad. But it's clear > to me that if I am listening to a 700Hz CW note, no amount of > audio roll-off at 4kHz or so is going to change the relative > levels of those first few harmonics. > > Just for fun, I ran the same test using an FT-847. The > results were very different. Firstly, harmonics were down at > -55 or better. Secondly, the even order products (2nd and > 4th) were louder than the odd ones. And lastly, the FT-847 > graph showed several close-in spurious alongside each > harmonic, which had been completely absent with the K3. > > I hope this all makes sense. And apologies if my use of > technical terms is not spot-on. I'm just an amateur, with no > training in electronics or radio ! > > Regards > > John G4ZTR > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Sverre > Holm (LA3ZA) > Sent: 20 December 2009 13:13 > To: [email protected] > Subject: Re: [Elecraft] [K3] K3 Receiver Noise Level -- > Evaluation and Adjustment > > > Concerning the last few days' discussion of noise and > artifacts, here is a spectral analysis plot of my K3's > output: http://www.qslnet.de/member/la3za/bilder/K3-CW-spectran.jpg > > First it shows the signal related artifacts in the 10-13 kHz > range as mentioned by Wayne N6KR below. It also shows line > noise at approximately every kHz (harmonics of 1.025-1.030 > kHz). The highest of these is at approx 2050 kHz and is at > about -40 dB relative to the main signal, i.e. at a level of > about 10^(-40/20) = 0.01 or 1%. Thus these lines could be > audible and be part of the explanation for the complaints > about the K3's sound. Apart from the lines, the background is > down to -60 dB above 2-3 kHz. > > It is interesting to note that my spectran plot has discrete > line noise as opposed to that of G4ILO in his blog from today > (http://www.g4ilo.com/blog.html), plot here: > http://www.g4ilo.com/uploaded_images/k3freqresponse-736797.gif > . His background noise level is similar to mine. > > Could this be due to differences in individual K3's as has > been hinted to on this list? > > My setup is: > K3 with PRE on at 14.102 MHz, RF gain at max, > CW with 400 Hz roofing filter and bandwidth set to 400 Hz, > AGC-F on and with AGC parameters SLP=9, THR=3, I use a lot of > averaging in Spectran to make the lines more visible as seen > from the setup info in my plot > > > wayne burdick wrote: > > > > This filter rolls off everything at about 4.5 > > kHz, including some low-level AF sampling artifacts from 10-14 kHz > > that some operators with excellent ears can hear. > > > > > ----- > Sverre, LA3ZA > > http://www.qslnet.de/member/la3za/K2/mod.html LA3ZA > Unofficial Guide to K2 modifications > -- > View this message in context: > http://n2.nabble.com/K3-Receiver-Noise-Level-Evaluation-and-Ad justment-tp418 7070p4194554.html Sent from the [K3] mailing list archive at Nabble.com. ______________________________________________________________ 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 __________ Information from ESET NOD32 Antivirus, version of virus signature database 4702 (20091219) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com __________ Information from ESET NOD32 Antivirus, version of virus signature database 4703 (20091220) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ______________________________________________________________ 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 ______________________________________________________________ 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
