There are some great articles on common mode chokes http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf
The other is K9YC's cookbook. Since I bought a VNA, I have been able to play with the choking value of some random chokes. Very interesting. Mike va3mw On Sat, Feb 14, 2015 at 6:57 PM, Harry Yingst via Elecraft < elecraft@mailman.qth.net> wrote: > There must be something special about 40 meters and micro-controllers. > My Aquarium Controller used to do a Reset when I transmitted on 40.The > cure for me was to wrap the control cable leads through Some Snap on chokes > I just installed my KAT500 today and considered taking thepower lead and > wrapping it around a snap on choke a few times. > > > From: "Jeff Hall, W6UX" <w...@ymail.com> > To: Elecraft Reflector <elecraft@mailman.qth.net> > Sent: Saturday, February 14, 2015 12:48 PM > Subject: [Elecraft] My KAT500 seems very sensitive to common mode RFI > > I have a Hex Beam and a 40m wire vertical w/ two elevated radials. I have > been fighting what appears to be a common mode RFI problem which causes the > KAT500 to continuously power cycle as long as the K3 is transmitting. > Generally this only occurs when driving my KPA500 amp beyond a certain > output level which differs for a given band and frequency. I am powering > the KAT500 with its own AC adapter. The problem can occur in both bypass > and auto mode. > > 7-10 ferrite beads on the coax attached to the KAT500 solved the power > cycling problem for my hex beam antenna and I successfully operate QRO in > bypass mode on all bands and modes. However the beads did not help with > the wire vertical. I can drive 300w into my dummy load with no ferrite > beads on the coax and the KAT500 is fine. > > The SWR is low enough I should be able to use these antennas to run the > KAT500 in bypass mode. If I put it in Auto mode the problem is > exacerbated. I can tune the wire vertical just fine with the KAT500 in > Auto mode at a tuning level of 25w from the K3. However, if I try to > transmit at 5w or more (SSB for example), the KAT500 starts to power cycle. > > I have no problem using the wire vertical if it is connected directly to > the K3's internal ATU. I observed that in this configuration, I could > still trip the power on the KAT500 even though it's not even connected to > that antenna, so I do believe this may be a common mode RF issue in the > shack. Somehow noise is finding its way into the KAT500. Several turns of > the AC power adapter's cord around a few ferrite beads hasn't helped either. > > I will at some point remove the KAT500 from the equation and see how > things work by directly connecting the K3 to the KPA500. I would like to > keep it in service as I might need it at the extreme band edges of the wire > vertical. > > The vertical wire is from W8AMZ. I don't believe there is any kind of > current Balun inside the feed point but I did place 10 ferrite beads over > the coax at the feed point. I'm running 100' of RG8X to this antenna. The > hex beam antenna is feed with LMR-400 and RG-213. > > So I don't know if the problem is specific to my vertical wire antenna and > feedline or if I should suspect a defective KAT500. > > Before I take the KAT500 offline, can anyone suggest some further > experiments to try? > > 73, Jeff W6UX > > ______________________________________________________________ > 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 > Message delivered to hlyin...@yahoo.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 > Message delivered to va...@portcredit.net > ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
