K3 Audio/RFI Feedback
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I'm experiencing audio/RFI feedback on 80M between the frequencies of 3650 KHz to 3850 KHz using a full-size 80M
vertical 100' from the radio. SWR is under 2:1. No difference if I use the built-in ATU. If I key the K3 and tap the mic once it goes into motorboating with full output (100W). The K3 monitor is set at 0. If I mute the PC line-in sound card there is no motorboating feedback. If I reduce the K3 mic setting from 30 toward 0 there is no motorboating feedback. If I reduce the PC line-in volume setting toward 0 there is no motorboating feedback. If I pull out the cable to the PC line-In there is no motorboating feedback. If I pull out the cable to the PC line-Out there is no motorboating feedback. At 50W setting the motorboating starts but is not self sustaining. At 90W setting the motorboating is self sustaining. Any suggestions on where next to look - or a solution? 73, Bud W3LL [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 |
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Do you have Mic+Line enabled in the K3? Sounds like RF on the cable between the K3 Line-Out and computer Line-In is being sent back to the K3 Line In jack. Improve the grounding of your station, including direct grounds on both the K3 and computer to the common ground point and add common mode chokes to both your feedline and the "Line In" connection to your computer. 73, ... Joe, W4TV > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Bud > Governale, W3LL > Sent: Tuesday, January 19, 2010 1:34 PM > To: [hidden email] > Subject: [Elecraft] K3 Audio/RFI Feedback > > > I'm experiencing audio/RFI feedback on 80M between the > frequencies of 3650 KHz to 3850 KHz using a full-size 80M > vertical 100' from the radio. > SWR is under 2:1. No difference if I use the built-in ATU. > > If I key the K3 and tap the mic once it goes into > motorboating with full output (100W). > > The K3 monitor is set at 0. > > If I mute the PC line-in sound card there is no motorboating > feedback. If I reduce the K3 mic setting from 30 toward 0 > there is no motorboating feedback. If I reduce the PC line-in > volume setting toward 0 there is no motorboating feedback. If > I pull out the cable to the PC line-In there is no > motorboating feedback. If I pull out the cable to the PC > line-Out there is no motorboating feedback. At 50W setting > the motorboating starts but is not self sustaining. At 90W > setting the motorboating is self sustaining. > > Any suggestions on where next to look - or a solution? > > 73, > > Bud W3LL > [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 ______________________________________________________________ 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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On Tue, 19 Jan 2010 14:57:16 -0500, Joe Subich, W4TV
wrote: >Improve the grounding of your station, >including direct grounds on both the K3 and computer >to the common ground point and add common mode chokes >to both your feedline and the "Line In" connection to >your computer. I agree with the advice, but I would not CALL it "grounding" -- that implies ground rods and all that mess. Rather, it is BONDING. It is unlikely that a connection to EARTH is part of a solution. BONDING is simply a very short, beefy copper connection between the CHASSIS of all of the equipment. Most important is between the chassis of the K3 and the chassis of the computer. See http://audiosystemsgroup.com/HamInterfacing.pdf And yes, a beefy coaxial ferrite choke as close as practical to the feedpoint of your antennas, and ferrite chokes on those audio interconnections. Those chokes must be wound so that they are resonant where you are having problems. Follow the guidelines for coaxial chokes in my Choke Cookbook in http://audiosystemsgroup.com/RFI-Ham.pdf and use the measured data in Appendix One for small wire chokes as a guide for chokes on the audio lines. Little clip-ons will not solve problems on 80M. You need lots of turns. 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 |
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Jim and all,
I agree too, but would like to clarify that the "bonding" should not be a "helter-skelter" connection of one piece of equipment to another. The most effective way of accomplishing that is to connect each piece of equipment in the shack to a common point (which may be optionally grounded or connected to a low impedance for RF (mother earth ground is only for lightning protection and personal safety, not RF grounding). That type of bonding connection is often referred to as a "star" configuration - as opposed to a 'daisy-chain' where the connection is from one piece of equipment to another. 73, Don W3FPR Jim Brown wrote: > On Tue, 19 Jan 2010 14:57:16 -0500, Joe Subich, W4TV > wrote: > > >> Improve the grounding of your station, >> including direct grounds on both the K3 and computer >> to the common ground point and add common mode chokes >> to both your feedline and the "Line In" connection to >> your computer. >> > > I agree with the advice, but I would not CALL it > "grounding" -- that implies ground rods and all that > mess. Rather, it is BONDING. It is unlikely that a > connection to EARTH is part of a solution. BONDING is > simply a very short, beefy copper connection between > the CHASSIS of all of the equipment. Most important is > between the chassis of the K3 and the chassis of the > computer. > > See http://audiosystemsgroup.com/HamInterfacing.pdf > > > 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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On Tue, 19 Jan 2010 17:55:04 -0500, Don Wilhelm wrote:
>I agree too, but would like to clarify that the "bonding" should not be >a "helter-skelter" connection of one piece of equipment to another. >The most effective way of accomplishing that is to connect each piece of >equipment in the shack to a common point (which may be optionally >grounded or connected to a low impedance for RF (mother earth ground is >only for lightning protection and personal safety, not RF grounding). >That type of bonding connection is often referred to as a "star" >configuration - as opposed to a 'daisy-chain' where the connection is >from one piece of equipment to another. There are really at least three different issues being addressed here. One of them is bonding for lightning protection and power system safety. The bonding that I was talking about to solve this issue is specifically aimed at solving what I suspect are pin 1 problems in the interconnected equipment. So the function of the bonding I recommended is to provide a low impedance path from chassis to chassis, so that RF is more likely to flow on the bonding conductors, chassis to chassis, than on interconnect cables (audio and control) into the circuit board and into the circuitry (by the pin 1 problem). That's also the reason for ferrite chokes on the interconnect cables. I certainly agree that a very low impedance bond of all equipment to a single point is a good idea. BUT -- I don't want the path from computer chassis to rig chassis to be any longer than necessary -- I don't want it to go to the center of the star and back, for example. I've seen this "star" approach implemented with a piece of copper pipe that runs along the back of a radio bench, with a dozen or so wires connected at points that are 6-10 ft apart. By contrast, my laptop sits on my operating bench between two K3s, and there's a short piece of #10 braid going to both rigs. The third reason for bonding is to minimize the audio voltage from chassis to chassis that is caused by leakage current in the power system, and that gets added to signal for any unbalanced connection between equipment. By bonding that equipment with big copper, we minimize that voltage (and divert the current away from pin 1 problems as well). As for my lightning protection bonding -- THAT'S where I implement the star. The rigs are bonded to the power outlet green wires with a short piece of braid (outlets are just below the bench). The power outlets are bonded to the coax entry panel, also just below the bench, which in turn goes to a half dozen ground rods. There's also a lot of coax routed through various switches to the coax entry panel (with feedthrough arrestors). That provides a DC bond, but those coaxes have a lot more inductance compared to the short braids. The power outlets run in EMT (thinwall steel conduit) back to the power panel, which has three ground rods of its own, on the other side of the small building that houses my shack, and some #4 copper runs around the perimeter of the shack to tie the ground rods together that way. Does this clarification allay your concerns? 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 |
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On Tue, 19 Jan 2010 18:27:27 -0800, "Jim Brown"
<[hidden email]> wrote: Jim, Thanks for that explanation of grounding methods. I got at least one of them right; I have a 1/2 inch copper pipe that runs along the back of the operating table that all of the equipment on the desk is grounded to. 73, Tom, N5GE [hidden email] K3 #806 with SUB RX, K3 #1055, PR6, XV144, XV432, KRC2, W1, 2 W2's and other small kits 1 K144XV on order http://www.n5ge.com http://www.swotrc.net >On Tue, 19 Jan 2010 17:55:04 -0500, Don Wilhelm wrote: > >>I agree too, but would like to clarify that the "bonding" should not be >>a "helter-skelter" connection of one piece of equipment to another. >>The most effective way of accomplishing that is to connect each piece of >>equipment in the shack to a common point (which may be optionally >>grounded or connected to a low impedance for RF (mother earth ground is >>only for lightning protection and personal safety, not RF grounding). >>That type of bonding connection is often referred to as a "star" >>configuration - as opposed to a 'daisy-chain' where the connection is >>from one piece of equipment to another. > >There are really at least three different issues being addressed here. >One of them is bonding for lightning protection and power system safety. >The bonding that I was talking about to solve this issue is specifically >aimed at solving what I suspect are pin 1 problems in the interconnected >equipment. So the function of the bonding I recommended is to provide a >low impedance path from chassis to chassis, so that RF is more likely to >flow on the bonding conductors, chassis to chassis, than on interconnect >cables (audio and control) into the circuit board and into the circuitry >(by the pin 1 problem). That's also the reason for ferrite chokes on the >interconnect cables. > >I certainly agree that a very low impedance bond of all equipment to a >single point is a good idea. BUT -- I don't want the path from computer >chassis to rig chassis to be any longer than necessary -- I don't want it >to go to the center of the star and back, for example. I've seen this >"star" approach implemented with a piece of copper pipe that runs along >the back of a radio bench, with a dozen or so wires connected at points >that are 6-10 ft apart. By contrast, my laptop sits on my operating bench >between two K3s, and there's a short piece of #10 braid going to both >rigs. The third reason for bonding is to minimize the audio voltage from >chassis to chassis that is caused by leakage current in the power system, >and that gets added to signal for any unbalanced connection between >equipment. By bonding that equipment with big copper, we minimize that >voltage (and divert the current away from pin 1 problems as well). > >As for my lightning protection bonding -- THAT'S where I implement the >star. The rigs are bonded to the power outlet green wires with a short >piece of braid (outlets are just below the bench). The power outlets are >bonded to the coax entry panel, also just below the bench, which in turn >goes to a half dozen ground rods. There's also a lot of coax routed >through various switches to the coax entry panel (with feedthrough >arrestors). That provides a DC bond, but those coaxes have a lot more >inductance compared to the short braids. The power outlets run in EMT >(thinwall steel conduit) back to the power panel, which has three ground >rods of its own, on the other side of the small building that houses my >shack, and some #4 copper runs around the perimeter of the shack to tie >the ground rods together that way. > >Does this clarification allay your concerns? > >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 ______________________________________________________________ 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
Amateur Radio Operator N5GE
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In reply to this post by Jim Brown-10
Jim (and all),
I believe we are both correct - and "it all depends...". The variety of "sneak" ground paths from one piece of equipment to another are numerous indeed (pin 1 problems are another source of trouble, and may confuse the real source as well). A star grounding system is the first place to start (IMHO), but additional bonding may be helpful in some situations. There is no one right answer - it all depends on your particular installation and your antenna installation. Is the problem RF or is it from ground current coupling from one piece of equipment to another? How to treat a particular problem will depend on the answer to that question. And, if it is caused by ground currents, the method to properly reduce them will vary from one installation to another (bonding the offending two pieces of equipment by a low impedance path may be required). A good starting point is in Jim Brown's website information, but the total answer is station to station dependent - this is not a case where "one size fits all". Some investigation along with a bit of trial and error may be required. Consider that "sneak" grounding paths are just what that indicates - they are unwanted and unlikely to be obvious to casual observations. 73, Don W3FPR Jim Brown wrote: > On Tue, 19 Jan 2010 17:55:04 -0500, Don Wilhelm wrote: > > >> I agree too, but would like to clarify that the "bonding" should not be >> a "helter-skelter" connection of one piece of equipment to another. >> The most effective way of accomplishing that is to connect each piece of >> equipment in the shack to a common point (which may be optionally >> grounded or connected to a low impedance for RF (mother earth ground is >> only for lightning protection and personal safety, not RF grounding). >> That type of bonding connection is often referred to as a "star" >> configuration - as opposed to a 'daisy-chain' where the connection is >> > >from one piece of equipment to another. > > There are really at least three different issues being addressed here. > One of them is bonding for lightning protection and power system safety. > The bonding that I was talking about to solve this issue is specifically > aimed at solving what I suspect are pin 1 problems in the interconnected > equipment. So the function of the bonding I recommended is to provide a > low impedance path from chassis to chassis, so that RF is more likely to > flow on the bonding conductors, chassis to chassis, than on interconnect > cables (audio and control) into the circuit board and into the circuitry > (by the pin 1 problem). That's also the reason for ferrite chokes on the > interconnect cables. > > I certainly agree that a very low impedance bond of all equipment to a > single point is a good idea. BUT -- I don't want the path from computer > chassis to rig chassis to be any longer than necessary -- I don't want it > to go to the center of the star and back, for example. I've seen this > "star" approach implemented with a piece of copper pipe that runs along > the back of a radio bench, with a dozen or so wires connected at points > that are 6-10 ft apart. By contrast, my laptop sits on my operating bench > between two K3s, and there's a short piece of #10 braid going to both > rigs. The third reason for bonding is to minimize the audio voltage from > chassis to chassis that is caused by leakage current in the power system, > and that gets added to signal for any unbalanced connection between > equipment. By bonding that equipment with big copper, we minimize that > voltage (and divert the current away from pin 1 problems as well). > > As for my lightning protection bonding -- THAT'S where I implement the > star. The rigs are bonded to the power outlet green wires with a short > piece of braid (outlets are just below the bench). The power outlets are > bonded to the coax entry panel, also just below the bench, which in turn > goes to a half dozen ground rods. There's also a lot of coax routed > through various switches to the coax entry panel (with feedthrough > arrestors). That provides a DC bond, but those coaxes have a lot more > inductance compared to the short braids. The power outlets run in EMT > (thinwall steel conduit) back to the power panel, which has three ground > rods of its own, on the other side of the small building that houses my > shack, and some #4 copper runs around the perimeter of the shack to tie > the ground rods together that way. > > Does this clarification allay your concerns? > > 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 > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.730 / Virus Database: 270.14.150/2632 - Release Date: 01/19/10 02:34:00 > > 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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Don Wilhelm wrote: > Jim (and all), > > I believe we are both correct - and "it all depends...". > The variety of "sneak" ground paths from one piece of equipment to > another are numerous indeed (pin 1 problems are another source of > trouble, and may confuse the real source as well). A star grounding > system is the first place to start (IMHO), but additional bonding may be > helpful in some situations. There is no one right answer - it all > depends on your particular installation and your antenna installation. > Is the problem RF or is it from ground current coupling from one piece > of equipment to another? How to treat a particular problem will depend > on the answer to that question. And, if it is caused by ground > currents, the method to properly reduce them will vary from one > installation to another (bonding the offending two pieces of equipment > by a low impedance path may be required). A good starting point is in > Jim Brown's website information, but the total answer is station to > station dependent - this is not a case where "one size fits all". Some > investigation along with a bit of trial and error may be required. > Consider that "sneak" grounding paths are just what that indicates - > they are unwanted and unlikely to be obvious to casual observations. > > 73, > Don W3FPR > > Jim Brown wrote: > >> On Tue, 19 Jan 2010 17:55:04 -0500, Don Wilhelm wrote: >> >> >> >>> I agree too, but would like to clarify that the "bonding" should not be >>> a "helter-skelter" connection of one piece of equipment to another. >>> The most effective way of accomplishing that is to connect each piece of >>> equipment in the shack to a common point (which may be optionally >>> grounded or connected to a low impedance for RF (mother earth ground is >>> only for lightning protection and personal safety, not RF grounding). >>> That type of bonding connection is often referred to as a "star" >>> configuration - as opposed to a 'daisy-chain' where the connection is >>> >>> >> >from one piece of equipment to another. >> >> There are really at least three different issues being addressed here. >> One of them is bonding for lightning protection and power system safety. >> The bonding that I was talking about to solve this issue is specifically >> aimed at solving what I suspect are pin 1 problems in the interconnected >> equipment. So the function of the bonding I recommended is to provide a >> low impedance path from chassis to chassis, so that RF is more likely to >> flow on the bonding conductors, chassis to chassis, than on interconnect >> cables (audio and control) into the circuit board and into the circuitry >> (by the pin 1 problem). That's also the reason for ferrite chokes on the >> interconnect cables. >> >> I certainly agree that a very low impedance bond of all equipment to a >> single point is a good idea. BUT -- I don't want the path from computer >> chassis to rig chassis to be any longer than necessary -- I don't want it >> to go to the center of the star and back, for example. I've seen this >> "star" approach implemented with a piece of copper pipe that runs along >> the back of a radio bench, with a dozen or so wires connected at points >> that are 6-10 ft apart. By contrast, my laptop sits on my operating bench >> between two K3s, and there's a short piece of #10 braid going to both >> rigs. The third reason for bonding is to minimize the audio voltage from >> chassis to chassis that is caused by leakage current in the power system, >> and that gets added to signal for any unbalanced connection between >> equipment. By bonding that equipment with big copper, we minimize that >> voltage (and divert the current away from pin 1 problems as well). >> >> As for my lightning protection bonding -- THAT'S where I implement the >> star. The rigs are bonded to the power outlet green wires with a short >> piece of braid (outlets are just below the bench). The power outlets are >> bonded to the coax entry panel, also just below the bench, which in turn >> goes to a half dozen ground rods. There's also a lot of coax routed >> through various switches to the coax entry panel (with feedthrough >> arrestors). That provides a DC bond, but those coaxes have a lot more >> inductance compared to the short braids. The power outlets run in EMT >> (thinwall steel conduit) back to the power panel, which has three ground >> rods of its own, on the other side of the small building that houses my >> shack, and some #4 copper runs around the perimeter of the shack to tie >> the ground rods together that way. >> >> Does this clarification allay your concerns? >> >> 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 >> ------------------------------------------------------------------------ >> >> >> No virus found in this incoming message. >> Checked by AVG - www.avg.com >> Version: 9.0.730 / Virus Database: 270.14.150/2632 - Release Date: 01/19/10 02:34:00 >> >> >> > ______________________________________________________________ > 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 > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.730 / Virus Database: 270.14.150/2632 - Release Date: 01/19/10 02:34:00 > > 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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