Ron, OK, now it appears I was mistaken when I said that that the hum was in both mics. I think I flubbed something up in my previous test due to the way that the macros are assigned to keys which led me to thinking that the hum occurred in both mics. But, I learned something in this...
One, don't try to use one of your macro assigned keys (in my case M2 and M1) while in the menu because that merely reassigns the key to the new menu entry. I made this mistake several times this morning. But, when I discovered it and then reset my macro definitions, I rediscovered that the HUM occurs in the front panel MH2 hand held mic only. I did this test several times to make sure I was not confusing things. I discovered something else that I did not know before. PTT is actuated by any of the methods of PTT. So, when I thought I had the headphones CM500 mic enabled I used my foot switch for push to talk and since that worked for some dumb reason I was thinking I had successfully switched from front panel to rear panel. But, I had not. I also discovered that I could use the hand mic (front panel) PTT switch even though my rear panel mic was being used. Now, after I discovered this, I realize that it is obvious but something that lead to my confusion. So, the problem occurs on the FRONT PANEL mic only and not the rear panel. And, the problem occurs when the K3 is in TOTAL isolation from all AC sources except for possibly me. I mean, I am holding the mic but then I don't think that is a cause of the hum because I tried it with a insulated hand and it still caused the hum on the front panel mic. I doubt that this is caused by wall-outlet type AC because I have erased all AC for some of my tests. And, besides, this problem seemed to occur .... OK, while writing that last sentence something occurred to me. Another change I had made on Wednesday after I had my good audio reports on the MH2 front panel mic was that I set the configuration for the band specific power levels to work with the KPA500. So, I just now went to test the mic and change that setting around but the hum is gone. I repeat, the hum is gone from the front panel mic. I now can't test the band specific power menu setting because I have no problem. But, I have a suspicion as to the cause now and I am going to do some other experiments. 73, phil On Jan 13, 2012, at 10:15 AM, Ron D'Eau Claire wrote: > Yeah, Phil, two mics doing it eliminates the easy idea of a bad wire in one > of them. > > When switching mics, be sure to physically disconnect the one you are not > using. An ungrounded mic hot lead might introduce hum, even if you have the > other mic enabled. > > Hand effects suggest a ground loop- either AC or RF. Being in TEST mode > eliminates RF, since you aren't making any. > > I'd start disconnecting things one at a time. If the hum is still there with > everything but the mic and power supply connected, you can be sure it's not > in the external gear. > > Do you have another power supply you can substitute? All it needs to do is > provide enough current for receive, since you are "transmitting" in TEST > mode. One possibility is that you'd lost filtering in the power supply. That > can produce different levels of hum from different mics, depending upon the > gain settings, etc. > > If it's clean on the alternate power supply, that leaves ONLY the K3, of > course. > > 73, > > Ron AC7AC > > -----Original Message----- > From: Phil Hystad [mailto:phys...@mac.com] > Sent: Friday, January 13, 2012 9:21 AM > To: Ron D'Eau Claire > Cc: 'Elecraft List' > Subject: Re: [Elecraft] K3 Hum on Audio... > > Ron, > > I have been able to do more tests. Unfortunately, it is in both mics but > not as strong in the Yamaha CM500 mic as in the MH2 but it is present. > > This morning I double checked all connections (most in the back). This > includes the key out to the KPA500, the plugs for the cm500, the external > speaker, my foot PTT switch, and even the svga cable to the KPA500. Nuts, > have not tested the serial port yet. However, absolutely no difference in > behavior. I can hear the hum on the speaker when I have the monitor gain > cranked up a little bit and keying the mic in Test mode. > > If I lay my hand on the top of the K3 the hum disappears. If I lay my hand > on the P3 sitting next to K3 the hum disappears but not as much. And, I can > do the same with other grounded equipment. I have checked my grounds and > they all seem to be pretty good. > > So, I am at a loss as to what to try next. This seemed to start on its own > Wednesday afternoon after my last SSB QSO. I say that because after that > QSO, I turned the rigs off and then the next day (Thursday, yesterday) I > turned the rigs on and the hum was there on my first SSB QSO at 6:30 PM. > > It sure seems like a grounding problem but I am not sure where to check > next. Also, this problem arose mysteriously close to me setting up the > KPA500 which I put on the air for the first time Wednesday early afternoon, > CW first and then a few SSB QSOs and I got good audio reports from both of > those QSOs. The hum though is definite, if someone were listening to my > audio with this hum they would hear it. > > 73, phil, K7PEH > > > On Jan 13, 2012, at 8:12 AM, Ron D'Eau Claire wrote: > >> Since it goes away when changing mics, it sounds a lot like a broken >> connection in the microphone connector. I used to fix those by the dozens > on >> shipboard VHF radios, equipped with hand-held mics. The complaint would be >> transmitting hum, no audio, or no PTT action, depending upon which wire >> broke. >> >> Usually the break was at the connector, but sometimes it's in the mic, >> depending upon which end had the best strain relief. Even found a broken >> wire inside the cable on rare occasions. >> >> 73, >> >> Ron AC7AC >> >> -----Original Message----- >> Subject: [Elecraft] K3 Hum on Audio... >> >> When the sun rose today and it seems that my K3 decided to put some hum on >> my audio. During a quick SSB contact tonight on 80 meters I was told > there >> was hum on my audio. This surprised me because yesterday I was involved > in >> two different SSB QSOs where I was particularly interested in audio > reports >> because I had just put the KPA500 on the air and wanted to know how it >> sounds. The audio reports yesterday, two different QSOs, were excellent. >> In fact one person wanted to know the rig because he said it sounded >> exceptional. >> >> Well, tonight, I get a report of what sounds like (the other guy reported) >> 60 cycle hum on my audio. Now, absolutely NOTHING is different from >> yesterday, same configuration and all. So, I am thinking maybe it has >> something to do with the KPA500. So, I put that in Standby and the hum is >> still there on the audio. The mic is the MH2 hand mic plugged into the >> front of the K3. >> >> So, I switch to my Yamaha CM500 headset and mic plugged into the rear of > the >> K3. No hum on that. So, the hum seems to do with the MH2 or maybe the >> front panel connection or something else. >> >> Does anyone know of what would cause this sudden thing and where I might > go >> to scope out the problem? I would be more suspicious if it were some rig >> that was new to me, or some mic that was new or something. But, it is not >> new and until now I have always had excellent reports. Like I said, >> yesterday the KPA500 was put on the air for the first time but the reports >> were excellent reports on audio, this problem appeared today in fact, > about >> 30 minutes ago. I turned the rig on at 6:15 PM and had the first QSO > where >> the hum was reported at 6:25 PM. >> >> 73, phil, K7PEH >> >> ______________________________________________________________ >> 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
