My KAT500 seems very sensitive to common mode RFI
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My KAT500 seems very sensitive to common mode RFI
 
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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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: My KAT500 seems very sensitive to common mode RFI
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On Sat,2/14/2015 9:48 AM, Jeff Hall, W6UX wrote:
> can anyone suggest some further experiments to try? Yes. The problem is that ferrite beads slipped onto a transmission line does NOT make an effective common mode choke. Those beads are inductive, and, depending on the length of the line and the operating frequency, many lines look capacitive. The inductance resonates with the capacitance, and the common mode current increases. To be effective as a common mode choke, we need a high value of common mode impedance, and the best way to get there is with a high value of RESISTANCE. We obtain that by forming a low-Q parallel resonant circuit -- we wind multiple turns of the feedline through a lossy ferrite toroid or clamp-on. The number of turns needed depends on the ferrite material and the operating frequency. The best ferrite material for the HF bands is Fair-Rite #31, because it has the lowest effective Q over the widest frequency range. Study k9yc.com/RFI-Ham.pdf and use the Cookbook as a guide to wind the chokes you need. The chokes are most effective at the feedpoint of your antennas. 73, Jim 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 Message delivered to [hidden email] |
Re: My KAT500 seems very sensitive to common mode RFI
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In reply to this post by Jeff Hall, W6UX-2
Don't know what kind of ferrite beads you are using, but many are
intended for VHF use and are not helpful at HF. Also, it is usually ineffective to just put a bead on the coax -- you should wrap multiple turns through a large toroid. Good ferrite materials for HF are #31 for 1.8-7 mHz and #43 for 14-30 mHz. Either one would probably work fine for both antennas. > 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 -- 73, Vic, 4X6GP/K2VCO Rehovot, Israel http://www.qsl.net/k2vco/ ______________________________________________________________ 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 Message delivered to [hidden email] |
Re: My KAT500 seems very sensitive to common mode RFI
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In reply to this post by Jim Brown-10
Thanks Jim, I'll give it a read and order up some mix-31 toroids. Does it surprise you the KAT500 is getting power cycled as I described? Is it really that sensitive? 10 of the ferrite beads I got from DXStore (rated for 150MHz or lower) work fine for 10m-20m. But no dice on 40m, so I guess the frequency is just too low for them to be effective (or perhaps I'd need like 50 of the suckers!)
-Jeff On Saturday, February 14, 2015 10:06 AM, Jim Brown <[hidden email]> wrote: On Sat,2/14/2015 9:48 AM, Jeff Hall, W6UX wrote: > can anyone suggest some further experiments to try? Yes. The problem is that ferrite beads slipped onto a transmission line does NOT make an effective common mode choke. Those beads are inductive, and, depending on the length of the line and the operating frequency, many lines look capacitive. The inductance resonates with the capacitance, and the common mode current increases. To be effective as a common mode choke, we need a high value of common mode impedance, and the best way to get there is with a high value of RESISTANCE. We obtain that by forming a low-Q parallel resonant circuit -- we wind multiple turns of the feedline through a lossy ferrite toroid or clamp-on. The number of turns needed depends on the ferrite material and the operating frequency. The best ferrite material for the HF bands is Fair-Rite #31, because it has the lowest effective Q over the widest frequency range. Study k9yc.com/RFI-Ham.pdf and use the Cookbook as a guide to wind the chokes you need. The chokes are most effective at the feedpoint of your antennas. 73, Jim 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 Message delivered to [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by Jeff Hall, W6UX-2
Hi Jeff does not suprise me.
Read the link in Jims email single beads do not cut it. ~73 Don KD8NNU FH#4107 -.- -.. ---.. –. –. ..- On Sat, Feb 14, 2015 at 1:56 PM, Jeff Hall wrote: > Thanks Jim, I'll give it a read and order up some mix-31 toroids. > Does it surprise you the KAT500 is getting power cycled as I > described? Is it really that sensitive? 10 of the ferrite beads I got > from DXStore (rated for 150MHz or lower) work fine for 10m-20m. But no > dice on 40m, so I guess the frequency is just too low for them to be > effective (or perhaps I'd need like 50 of the suckers!) > -Jeff > > > > On Saturday, February 14, 2015 10:06 AM, Jim Brown > <[hidden email]> wrote: > On Sat,2/14/2015 9:48 AM, Jeff Hall, W6UX wrote: >> can anyone suggest some further experiments to try? > > Yes. The problem is that ferrite beads slipped onto a transmission > line does NOT make an effective common mode choke. Those beads are > inductive, and, depending on the length of the line and the operating > frequency, many lines look capacitive. The inductance resonates with > the capacitance, and the common mode current increases. > > To be effective as a common mode choke, we need a high value of common > mode impedance, and the best way to get there is with a high value of > RESISTANCE. We obtain that by forming a low-Q parallel resonant > circuit -- we wind multiple turns of the feedline through a lossy > ferrite toroid or clamp-on. The number of turns needed depends on the > ferrite material and the operating frequency. The best ferrite > material for the HF bands is Fair-Rite #31, because it has the lowest > effective Q over the widest frequency range. > > Study k9yc.com/RFI-Ham.pdf and use the Cookbook as a guide to wind > the chokes you need. The chokes are most effective at the feedpoint of > your antennas. > > 73, Jim 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 > Message delivered to [hidden email] > ______________________________________________________________ > 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 > Message delivered to [hidden email] 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 Message delivered to [hidden email] |
Re: My KAT500 seems very sensitive to common mode RFI
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In reply to this post by Jeff Hall, W6UX-2
Does this mean that your KAT is placed between the K3 and the KPA?
OZ4UN Sendt fra min iPhone > Den 14/02/2015 kl. 18.49 skrev Jeff Hall, W6UX <[hidden email]>: > > by directly connecting the K3 to the KPA500. ______________________________________________________________ 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 Message delivered to [hidden email] |
Re: My KAT500 seems very sensitive to common mode RFI
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In reply to this post by Jeff Hall, W6UX-2
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" <[hidden email]> To: Elecraft Reflector <[hidden email]> 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] |
Re: My KAT500 seems very sensitive to common mode RFI
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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 < [hidden email]> 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" <[hidden email]> > To: Elecraft Reflector <[hidden email]> > 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:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > > > > ______________________________________________________________ > 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 > Message delivered to [hidden email] > 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 Message delivered to [hidden email] |
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In reply to this post by Elecraft mailing list
On Sat, 14 Feb 2015 23:57:18 +0000 (UTC), Harry Yingst via Elecraft wrote:
> There must be something special about 40 meters and micro-controllers. I learned years ago that there is something special about 40 meter RF. I've gotten into more "stuff" when on 40 meters than anything else since 21 MHz TV IFs went away. I've melted things in radios while barefoot too. I don't know what it is, but lots of things seem to be sensitive to that band. Gary ______________________________________________________________ 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 Message delivered to [hidden email] |
Re: My KAT500 seems very sensitive to common mode RFI
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In reply to this post by Michael Walker
Thanks everyone for their replies to my problem. I read Jim Brown's paper this afternoon and have ordered some mix 31 Big Clamps. I'll try putting one at each end of the 40m coax feedline (RG8X) with the prescribed number of turns.
-Jeff On Saturday, February 14, 2015 4:22 PM, Michael Walker <[hidden email]> wrote: 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 <[hidden email]> 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" <[hidden email]> To: Elecraft Reflector <[hidden email]> 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] |
Re: My KAT500 seems very sensitive to common mode RFI
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Do you have chokes on the power, AUX, and Serial Cables to the KAT500?
From: Jeff Hall <[hidden email]> To: Michael Walker <[hidden email]>; Harry Yingst <[hidden email]> Cc: Elecraft Reflector <[hidden email]> Sent: Saturday, February 14, 2015 9:22 PM Subject: Re: [Elecraft] My KAT500 seems very sensitive to common mode RFI Thanks everyone for their replies to my problem. I read Jim Brown's paper this afternoon and have ordered some mix 31 Big Clamps. I'll try putting one at each end of the 40m coax feedline (RG8X) with the prescribed number of turns. -Jeff On Saturday, February 14, 2015 4:22 PM, Michael Walker <[hidden email]> wrote: 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 <[hidden email]> 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" <[hidden email]> To: Elecraft Reflector <[hidden email]> 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] |
Re: My KAT500 seems very sensitive to common mode RFI
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I have several turns of the AC adapter cord through two snap on beads. I don't have anything on the AUX cables at this time, but that is something I should probably check. I ordered 6 of the Mix 31 Big Clamp toroids from KF7P. For the 40m vertical I'll place one choke at the feedpoint and see if the problem is resolved. If not, I'll place another choke at the KAT500. If I still have a problem, another choke will be placed at the output of the KPA500. If that still doesn't work, another choke will be placed at the output of the K3. Once I have suppressed the common mode RF on the vertical, I'll try replacing the string of ferrite beads on my hex beam's coax with a Big Clamp choke at the KAT500.
-Jeff W6UX On Saturday, February 14, 2015 6:25 PM, Harry Yingst <[hidden email]> wrote: Do you have chokes on the power, AUX, and Serial Cables to the KAT500? From: Jeff Hall <[hidden email]> To: Michael Walker <[hidden email]>; Harry Yingst <[hidden email]> Cc: Elecraft Reflector <[hidden email]> Sent: Saturday, February 14, 2015 9:22 PM Subject: Re: [Elecraft] My KAT500 seems very sensitive to common mode RFI Thanks everyone for their replies to my problem. I read Jim Brown's paper this afternoon and have ordered some mix 31 Big Clamps. I'll try putting one at each end of the 40m coax feedline (RG8X) with the prescribed number of turns. -Jeff On Saturday, February 14, 2015 4:22 PM, Michael Walker <[hidden email]> wrote: 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 <[hidden email]> 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" <[hidden email]> To: Elecraft Reflector <[hidden email]> 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] |
Re: My KAT500 seems very sensitive to common mode RFI
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Jeff and all,
I see many hams reporting placing common mode chokes on AC lines, DC lines, AUX cables and other lines in the shack. I am of the opinion that the proper use of common mode chokes is on the antenna feedlines. With coax fed antennas, a choke right at the feedpoint and with parallel line non-resonant antennas, at the point of transition from parallel line to coax. You may not notice a problem at lower power, but if the power is increased to 500 watts (or to the legal limit), problems not apparent at lower power begin to 'raise their ugly heads'. Chokes placed in the antenna system locations will reduce the amount of RF getting back into the shack and will reduce the need for chokes on the shack lines themselves. Of course, if the antenna radiation is coming directly into the shack (such as from an antenna in close proximity to the shack), then you may still need additional chokes in the shack. Those using offset center fed dipoles or end fed dipoles will have to take more extreme measures (use the K9YC common mode chokes at the antenna feedpoint and at the feedline entry point to the shack). Those antennas are 'infamous' for creating 'RF in the Shack'. It may not be a problem at 100 watts, but the problem grows exponentially as the power is increased. 73, Don W3FPR On 2/14/2015 9:46 PM, Jeff Hall wrote: > I have several turns of the AC adapter cord through two snap on beads. I don't have anything on the AUX cables at this time, but that is something I should probably check. I ordered 6 of the Mix 31 Big Clamp toroids from KF7P. For the 40m vertical I'll place one choke at the feedpoint and see if the problem is resolved. If not, I'll place another choke at the KAT500. If I still have a problem, another choke will be placed at the output of the KPA500. If that still doesn't work, another choke will be placed at the output of the K3. Once I have suppressed the common mode RF on the vertical, I'll try replacing the string of ferrite beads on my hex beam's coax with a Big Clamp choke at the KAT500. > -Jeff W6UX > ______________________________________________________________ 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 Message delivered to [hidden email] |
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I echo Don's comment. My MC-60 mic used to be very sensitive to RF in the
shack and my monitor used to click on and off, until I placed common mode chokes on the coax leaving the antenna tuner, and on the coax feeding a balun outside the shack. (Antenna is an open-wire-fed 80 meter doublet.) I no longer have any discernible RF problems, save for my amplified audio getting a weak buzz when transmitting high power - and that's probably from radiated RF, not common mode. I have no other chokes on other cables. Monty K2DLJ Jeff and all, I see many hams reporting placing common mode chokes on AC lines, DC lines, AUX cables and other lines in the shack. I am of the opinion that the proper use of common mode chokes is on the antenna feedlines. ______________________________________________________________ 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 Message delivered to [hidden email] |
Re: My KAT500 seems very sensitive to common mode RFI
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To re-enforce what has been said already, I read the Contest Clipper Club
report and then a few others, and to summarize, here is what I found: - I ordered a few dozen Mix 43 and Mix 31 chokes online. I think I ordered 24 of each type and used the model numbers in the CCC document I quoted earlier. - I solved RF feedback issues (like bad SWR readings) but choking feedlines. This was really apparent in the mobile when the screwdriver would never seem to resolve turning on 40m. Once I choked the control line and the feedline, the antenna has never worked better. - Next was receiving. I had to start choking things in the station and around the station. I made good use the FT817 and the break panel to see what noises disappeared as I started to flip breakers in the house. I'm a believer in the right choke for both receiving issues and transmitting issues. I also believe that it is even more critical than a good ground. Mike va3mw On Sun, Feb 15, 2015 at 6:31 AM, MontyS <[hidden email]> wrote: > I echo Don's comment. My MC-60 mic used to be very sensitive to RF in the > shack and my monitor used to click on and off, until I placed common mode > chokes on the coax leaving the antenna tuner, and on the coax feeding a > balun outside the shack. (Antenna is an open-wire-fed 80 meter doublet.) I > no longer have any discernible RF problems, save for my amplified audio > getting a weak buzz when transmitting high power - and that's probably from > radiated RF, not common mode. I have no other chokes on other cables. > > Monty K2DLJ > > Jeff and all, > > I see many hams reporting placing common mode chokes on AC lines, DC > lines, AUX cables and other lines in the shack. > > I am of the opinion that the proper use of common mode chokes is on the > antenna feedlines. > ______________________________________________________________ > 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 > Message delivered to [hidden email] > 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 Message delivered to [hidden email] |
Re: My KAT500 seems very sensitive to common mode RFI
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In reply to this post by Jeff Hall, W6UX-2
The W8AMZ is a 1/4 wave vertical with two radials. This means that all of the return currents are expected to go through those two wires. Except there is a third that is very appealing to the antenna - the coax shield. You might try adding more radials. That will distribute the return current among more radials, which will also reduce the return current on the outside of the coax. In addition, choking at the feed point is very important, as is choking at the shack entry point.
Quarter-wave verticals are very difficult to tame when it comes to return currents and coax. It is doable, but patience and lots of experimenting are required. The reason you see it with high power is quite simply that there is more power and the currents are much higher. Remember, the power is the square of the current, so the problem goes up exponentially with power. The KAT500 is actually no more sensitive than any other ATU to shield current problems, but we ask so much more of it than a 150 watt ATU. Getting rid of the shield currents before they get to the KAT500 and making sure the SWR on the antenna coax going to the KAT is within proper range is vital to keeping everyone happy. 73, JackB, W6FB > On Feb 14, 2015, at 6:46 PM, Jeff Hall <[hidden email]> wrote: > > I have several turns of the AC adapter cord through two snap on beads. I don't have anything on the AUX cables at this time, but that is something I should probably check. I ordered 6 of the Mix 31 Big Clamp toroids from KF7P. For the 40m vertical I'll place one choke at the feedpoint and see if the problem is resolved. If not, I'll place another choke at the KAT500. If I still have a problem, another choke will be placed at the output of the KPA500. If that still doesn't work, another choke will be placed at the output of the K3. Once I have suppressed the common mode RF on the vertical, I'll try replacing the string of ferrite beads on my hex beam's coax with a Big Clamp choke at the KAT500. > -Jeff W6UX > > On Saturday, February 14, 2015 6:25 PM, Harry Yingst <[hidden email]> wrote: > > > Do you have chokes on the power, AUX, and Serial Cables to the KAT500? > > > > > > From: Jeff Hall <[hidden email]> > To: Michael Walker <[hidden email]>; Harry Yingst <[hidden email]> > Cc: Elecraft Reflector <[hidden email]> > Sent: Saturday, February 14, 2015 9:22 PM > Subject: Re: [Elecraft] My KAT500 seems very sensitive to common mode RFI > > Thanks everyone for their replies to my problem. I read Jim Brown's paper this afternoon and have ordered some mix 31 Big Clamps. I'll try putting one at each end of the 40m coax feedline (RG8X) with the prescribed number of turns. > -Jeff > > On Saturday, February 14, 2015 4:22 PM, Michael Walker <[hidden email]> wrote: > > > 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 <[hidden email]> 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" <[hidden email]> > To: Elecraft Reflector <[hidden email]> > 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:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > > > > ______________________________________________________________ > 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 > Message delivered to [hidden email] > > > > > > > > > ______________________________________________________________ > 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 > Message delivered to [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] |
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