Delete this message now if you are sick and tired of hearing about noisy receivers.
I have made three recordings of three different receivers tuned to 40 meter band noise, all with CW bandwidth of (nominally) 500 Hz centered near 550 Hz sidetone, all with the RF gain full up. One of the three is a K3. If you care to listen to them and then report back with which one you think is the K3, I would be most interested in hearing from you. The files are available at Hector's web site at the following link: http://www.ad4c.us/Elecraft%20K3/shared%20files%20from%20K3%20users/W6LX%20recordings_/ and are called, "#1.wav", "#2.wav" and "#3.wav". (Thanks very much, Hector, for giving up some temporary space to make these available to everybody.) I have asked Hector to delete them after several days. This is not a 'trick' test... I firmly believe all of you that have reported listener's fatigue from the K3... I am trying to determine qualitatively how much noisier a K3 is perceived compared to some other common ham receivers. I wish I had more receivers to sample, but these were all I could immediately get my hands on. In light of the recent announcement that a new DSP board for the K3 with low pass filter is now available, and the fact that many folks were wondering publicly if they really needed the upgrade, perhaps this test will also help you decide. If it is not obvious from these recordings which of the three is the (offensive) K3, then perhaps you are immune to the artifacts and don't need the upgrade. Since these recordings were made, two additional theories have been put forth on this reflector. The first is that even if you can't hear the high frequency artifacts, they may still cause listener's fatigue-- which is quite a provocative idea; the second is that the artifacts are really only a problem under "modulated conditions" -- I took this to mean when a signal present within the receiver bandwidth. I may make new recordings in the future to test these hypotheses. Because it was important to preserve the full 20 kHz audio bandwidth-- not just the CW bandwidth-- these are 44.1 kHz .wav files that I deliberately did not convert to MP3-- and so to keep the file sizes reasonable they are only 15 seconds each... not a whole lot to go by, but I hope enough to make a decent assessment. (Certainly long enough for someone who hears the artifacts to identify them.) They were all recorded straight from the headphone output of each of the three receivers. All recorded within a few minutes of each other on 7057.0 kHz in the evening. (Incidentally, the K3's DSP board is a Rev. B board.) To save reflector bandwidth, why don't you reply to me privately and I will compile and report the group's results. Thanks for your consideration, and I'm looking forward to receiving your reports! Regards, Al W6LX ______________________________________________________________ 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
