Re: [Elecraft] KPA 500 Hum PC Speakers.
The hum is due to magnetic field in close proximity of the speaker...usually. Sometimes RF gets into them usually on the power cord. Ferrite fixes this, moving the speakers fixes the former. Chuck, KE9UW -- View this message in context: http://elecraft.365791.n2.nabble.com/Re-KPA-500-Hum-PC-Speakers-tp6642295p6645333.html Sent from the Elecraft 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] KPA 500 Hum PC Speakers.
RFI problems with the computer speakers are generally due to the absence of the bypass components recommended by the amplifier chip designers. I have seen several inexpensive computer speakers with holes for the bypass caps on the circuit board (the chip maker's reference design) but no parts. Generally, all it takes to make the speakers bullet proof is adding the missing parts. In the worst cases adding a couple molded 100 uH or 1 mH chokes in series with the speaker lines inside the amplifier case resolved the remaining RFI problems. 73, ... Joe, W4TV On 8/2/2011 11:57 AM, ke9uw wrote: The hum is due to magnetic field in close proximity of the speaker...usually. Sometimes RF gets into them usually on the power cord. Ferrite fixes this, moving the speakers fixes the former. Chuck, KE9UW -- View this message in context: http://elecraft.365791.n2.nabble.com/Re-KPA-500-Hum-PC-Speakers-tp6642295p6645333.html Sent from the Elecraft 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: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
Re: [Elecraft] KPA 500 Hum PC Speakers.
Note the changed subject. Computer speakers are cheaply made, no shielding. If you are lucky won't have issues. In your cases, suggest moving them away from equipment. Don't forget that stray rf loves audio as well. Grounding, antenna location, etc. can all play a role. (I have no hum while transmitting. I did add an isolator between the K3 and amplified PC Speakers.) 73, Bill K9YEQ -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of n...@n5ge.com Sent: Monday, August 01, 2011 2:14 PM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] KPA 500 Hum Klaus, Are you sure it is the KPA500? My computer speakers in the shack will hum when using any of my HF amplifiers on CW. 73, Tom Amateur Radio Operator N5GE ARRL Lifetime Member QCWA Lifetime Member On Mon, 1 Aug 2011 07:33:05 +, Klaus Koppendorfer k...@ccf.net wrote: Last week i assembled the kpa500 of oe6rdd when we transmit we hear a realy loud hum (50hz) in the rythm of the cw signals i have compared this with my own kpa-500 and there is no hum i have tried to loosen the big srew which holds the tranformer with no result any ideas ?? __ 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
