Dave, Please understand that my audio recording need has nothing to do with my K3 or with ham radio. The USB/RS232 line connecting the computer with the K3 is there, but the K3 is powered down. And I have no bonding between the chassis of the two. I never had a problem, but then I never tried to record radio output on the computer, and I never tried to feed a computer voice recording to the K3. I have done some PSK, using a previous desktop computer as well as the old laptop, but then I was always using a homebuilt interface that contains isolation transformers. Yes I know, overkill, but that interface was built before I got the K3. I am currently not interested in doing PSK or other digital modes again, but when I get the urge, I will probably have purchased an external soundcard that will be better than the current computer's motherboard-integrated audio. Just for fun, because you seem to focus on it, I made an experiment: I disconnected the RS-232 from the computer by unplugging its USB. Then I made a recording using a dynamic microphone and found the same noise as before. The powered speakers were disconnected from the computer during the recording. Still connected were other items such as monitor, keyboard, mouse, two printers and wired Ethernet. It would certainly be possible to test with more stuff disconnected, but that is all I have time for right now.
When you mention twang on the audio, I assume you were recording the audio on the computer while using the noise reduction associated with its microphone input? That is the only condition under which I hear the twang (and then it replaces the noise). If I turn the noise reduction off, the twang disappears and the noise comes back. Erik K7TV David Gilbert wrote: OK, now that sounds a lot like the issues I had when I first began using pre-recorded .wav files for contesting. I got several reports of "hum", "noise", or "whine" on my transmitted signal ... all of which went away when I disconnected the RS-232 cable from between the computer and the K3. As I have mentioned several times here before, it took a very short piece of shielded braid between the chassis of the K3 and the chassis of the computer to fix it so that I could reconnect the RS-232 cable without issues. I started with a couple of feet of braid and had to go all the way down to eight inches before I could no longer notice the problem. You don't say what measures you've taken to bond the chassis of your K3 to your computer, but that would be my first suggestion. Your symptoms sound almost identical ... even with respect to the noise during pauses and the metallic twang at the end of words. Regarding sound cards for SDR use, certainly the great majority of cards out there would have major deficiencies ... most especially for noise, but also for dynamic range and sampling rate. And as you say, many don't even have stereo inputs. N8LP keeps a list of recommended cards on his web site with good information on the pros and cons of each. 73, Dave AB7E ______________________________________________________________ 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
