I've spent a bit more time investigating this noise, following my initial response to David.
The noise sounds rather like a buzz saw. It is quite audible on the K3 speaker, it is strong enough to move the S meter, and it's visible on the P3. There is not just one frequency, but the noise is every 19kHz (approx) across the band. The noise goes away if:- 1. I turn the P3 off 2. I remove the 2m antenna The noise reduces if:- 1. I disconnect the BNC at the K3 IF Out connector. I already have chokes on the DC lead to the P3. I think at this stage I should also make it clear that I have a highly sensitive 2m system with masthead preamplifier, and four eight element yagis which are at present quite close to ground level. Regards John G4ZTR -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jim Brown Sent: 23 March 2011 19:20 Cc: [email protected] Subject: Re: [Elecraft] [K3] Noise from P3 On 3/23/2011 11:56 AM, John Lemay wrote: > It seems to me that the noise is being radiated by the screen itself, and no > amount of cabinet scraping will reduce this. That's entirely possible -- but it's also possible that the cables are involved. Many RFI problems have more than one cause, or more than one component, or a combination of causes, both of which must be present for the RFI to happen. In this example, a hand or finger next to the display allows RF to capacity-couple to the body, and the resulting RF current radiates the noise. Take the fingers away, and if there's still noise, another coupling mechanism may be present. On the other hand, I've never felt the urge to have my fingers next to the P3 screen. :) I don't operate 2M for weak signal work, because I'm blocked by a high ridge to all of North America, so I can't comment on noise from my own display. :) I don't recall details of the P3 construction, nor the display, but the display is a potential break in shielding, and even a potential RFI source. Ideally, the display should be bonded to the shielding enclosure and be constructed in a manner that there is no break in the shielding, and any current driving the display should flow in a loop with very small area to minimize any magnetic field. 73, Jim K9YC ______________________________________________________________ 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 5978 (20110323) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com __________ Information from ESET NOD32 Antivirus, version of virus signature database 5978 (20110323) __________ 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
