Re: Computer RFI in K2 -- Follow-Up
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Re: Computer RFI in K2 -- Follow-Up
 
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I've definitely verified that it's the polling from the two laptops. Increasing the polling interval correspondingly decreases the cycling frequency. It's quite tolerable with the polling set at 50, but it would be nicer not to have the problem at all. I'm still open to any advice from anyone who's dealt with this in the past.
--Jeff, K6JW ----- Original Message ----- From: J. Wolf To: [hidden email] Sent: Tuesday, July 06, 2010 1:13 PM Subject: Computer RFI in K2 Recently, I made up the cable to connect my K2/100 to both the KAT100 ATU and my laptop. Everything works just fine...except for RFI from the computer to the radio when any of several logging programs is loaded (N1MM and CommCat being my two main programs). It sounds like a rapidly cycling change in the radio's noise level, and the S-meter reflects this, going from a baseline band noise level up to S9 with a period of just under a second. I've tried ferrite beads on everything, better grounding of the radio, and just connecting to the computer without the ATU, but nothing seems to have worked. The RFI isn't getting in via the coax feedline, since disconnecting it has no effect. In desperation, I tried a different laptop but got the same problem. The connection is via a serial to USB converter, and I've tried two different ones with no resolution of the problem. There's NO problem when the computer is running without either of the logging programs booted, so I'm guessing this might have something to do with polling. Does anyone have any experience with this and, if so, any suggestions? Jeff, K6JW ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Computer RFI in K2 -- Follow-Up
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On Tue, 6 Jul 2010 19:43:21 -0700, J. Wolf wrote:
>I'm still open to any advice from anyone who's dealt with this in the past. There are several possible mechanisms for coupling the RFI you're hearing. 1) Direct radiation from the wiring inside the computer because it is either poorly shielded or has poor circuit board layout. 2) Common mode radiation from one or more of the cables connected to the computer. This is made worse by serial ports with pin 1 problems, and by serial cables that are not twisted pairs. A big dent can be made in #2 with suitable common mode chokes on that wiring, and by building a serial cable according to the instructions in my RFI tutorial. http://audiosystemsgroup.com/RFI-Ham.pdf For the serial cable, see the Chapter on Solving Problems in the Shack. The only solutions for #1 are replacing the computer or the bucket treatment. 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Computer RFI in K2 -- Follow-Up
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In reply to this post by J.A. Wolf, MD, K6JW
> I've definitely verified that it's the polling from the two laptops. Increasing the polling interval correspondingly decreases the cycling frequency. It's quite tolerable with the polling set at 50, but it would be nicer not to have the problem at all. I'm still open to any advice from anyone who's dealt with this in the past. My experience with reports of this kind generally resolve to an open ground/shield on the USB cable. The first thing to try is a different USB cable (if the cable is not "captive") and a different serial converter if you can't replace the cable. The data rate on the USB side of the serial converter is higher than that on the RS-232 side and generally causes the largest part of the noise problem. 73, ... Joe, W4TV On 7/6/2010 10:43 PM, J. Wolf wrote: > I've definitely verified that it's the polling from the two laptops. > Increasing the polling interval correspondingly decreases the cycling > frequency. It's quite tolerable with the polling set at 50, but it > would be nicer not to have the problem at all. I'm still open to any > advice from anyone who's dealt with this in the past. > --Jeff, K6JW > ----- Original Message ----- > From: J. Wolf > To: [hidden email] > Sent: Tuesday, July 06, 2010 1:13 PM > Subject: Computer RFI in K2 > > > Recently, I made up the cable to connect my K2/100 to both the KAT100 ATU and my laptop. Everything works just fine...except for RFI from the computer to the radio when any of several logging programs is loaded (N1MM and CommCat being my two main programs). It sounds like a rapidly cycling change in the radio's noise level, and the S-meter reflects this, going from a baseline band noise level up to S9 with a period of just under a second. I've tried ferrite beads on everything, better grounding of the radio, and just connecting to the computer without the ATU, but nothing seems to have worked. The RFI isn't getting in via the coax feedline, since disconnecting it has no effect. In desperation, I tried a different laptop but got the same problem. The connection is via a serial to USB converter, and I've tried two different ones with no resolution of the problem. There's NO problem when the computer is running without either of the logging programs booted, so I'm guess ing > this might have something to do with polling. Does anyone have any experience with this and, if so, any suggestions? > Jeff, K6JW > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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