Re: [digitalradio] Re: RF feedback with interface
The best luck I've had getting rid of RFI in my shack through audio lines is the filter chokes sold by Radio Shack. They cost around $9 for a pair, and they are about 2 inches square, and snap open so audio lines can be wrapped around the inside. I'll admit that I had to use two of them the last time, but it cured the RFI problem right quick! I also have a Butternut vertical about 40 feet from the shack, and (at the time) had a double-sized G5RV with the apex at 35 feet, about 40 feet from the shack, with the twin-lead only 25 feet from the shack. The G5RV was the culprit, but the filters got rid of the problem. I also have a separate earth ground approximately 20 feet from the rig - an eight foot copper rod driven into part of the cellar floor. Hope you can get it fixed! I know how irritating it can be! 73 es GL Dave KB3MOW > Antenna that gives me the main problem is an inverted vee dipole with > apex at about 35 feet and ends at about 15 feet high. I have a Butternut > vertical located about 150 out from the house that does not seem to > cause any problems, but for close in (< 200 miles) the dipole is > indispensable. It is of course throwing RF back to the shack as the apex > is only 40 feet in horizontal distance to the base of the tower on the > end of the garage. > > Everything is coax fed. I have tried "balanced" lines with tuners off > and on over the years, but it is less convenient for routing and can be > more of a problem with RF feedback too. I don't use any separate > grounding and may have to try it as the main RF ingress seems to be the > audio lines from the computer. > > If I disconnect from the computer (even leaving the DIN plug connected > with the ferrite rod on that line which is a few feet long) it seems to > clear up. It is only a foot of cable between the sound card and my 1:1 > isolation transformers. I suspect that if I put a scope on the shield > from the sound card I won't like what I see. > > It would be about 20 feet to run a ground to the outside SPG and I have > also been skeptical that would help a lot. For some lightning > protection, I disconnect my rigs from the antenna switch which grounds > all unused feedlines, but of course, only through their shields, but at > least it makes them common to each other. I admit that for 160/80 and > maybe 40 meters, a 20 foot run is not too bad for "grounding." > > 73, > > Rick, KV9U > > > > > > > > > > Brian A wrote: >> Rick, >> >> Welcome to the world of QRO. >> >> You didn't mention your antenna system or band. Common problems guys >> have: >> 1) open wire line with goofy unbalanced antenna attached. >> 2) poor grounding of the rig. (A fat short ground connecting amp and >> rig needed.) Corroded connections at the ground stake. Old ground >> stake which has had the copper clad corroded away. >> 3) no balun or at least a coil of coax at the feedpoint of balanced >> antennas. The number of turns varies with freq. More turns isn't >> necessarily better. Unbalanced antennas often need a string of >> ferrites at the feed point around the coax. >> 4) tuners trying to tune a too short antenna. >> 5) indoor antennas or antennas too close to the house. >> >> Too bad one can't take a can of aerosol spray, spray the air and see >> the concentrations of RF. >> >> A severe RFI problem appeared over night here once. It turned out >> that the ground to the xcvr had worked loose with time. Tightening it >> up solved the problem. >> >> If you only operate one band, a 1/4 wave counterpoise connected to the >> amp may help. Just run it under the rug. >> >> Is the computer case grounded? >> >> 73 de Brian/K3KO >> >> >> --- In digitalradio@yahoogroups.com, Rick <[EMAIL PROTECTED]> wrote: >> >>> Until recently, I only ran 100 watts maximum power, but I did purchase >>> an Ameritron ALS-600 amplifier to help me mostly on lower band SSB. I >>> was using the rig today and testing out my new Heil 781 mike that I am >>> using to replace my ICOM hand mike. And we were testing various >>> >> settings >> >>> on the rigs bass and treble transmit controls. >>> >>> During the test the other stations suddenly noticed rather severe RFI >>> feedback. I switched back to the old mike but the problem was still >>> there. Having had a lot of problems in the past, I knew that this was >>> likely due to RF getting into my digital control or audio lines from >>> >> the >> >>> computer sound card to the rig. >>> >>> Turning off the amplifier did stop the RFI, so it is apparently due to >>> the increased RF. Also, after unplugging the audio line in and out to >>> the ICOM 756 Pro 2, which is via a DIN plug on the back of the rig, the >>> problem went away. Even with the amplifier running at full power. The >>> CI-V was still connected. >>> >>> I still can not explain why no one noticed the problem earlier as they >>> were critiquing my audio and would have noticed it. >>> >>> On both my CI-V and my audio lines I have about 20 turns of the cables >>> around thei
Re: [digitalradio] Re: RF feedback with interface
Hi All: I hve had same problems,, and everything here is by the book.. single point ground antennas 1.1:1 etc etc etc RF only occured on 20 and 40 ( but entire band..) to solve problem I bought 2 T-4 un-un balums, problem is gone running al811h about 800 pep and mostly around 220 wtts digital pictures with the un un's out side all RF is gone ( and doing digital pictures you notice every little bit-- trust me) Radio Works has a excellent paper on line about RF and solutions.. http://radioworks.com/nindex.html un-un's aren't cheap ( about 40 bucks each) but then quality never is.. read his page before you deceide. Garrett / AA0OI - Original Message From: Brian A <[EMAIL PROTECTED]> To: digitalradio@yahoogroups.com Sent: Thursday, November 8, 2007 10:22:38 AM Subject: [digitalradio] Re: RF feedback with interface Rick, Welcome to the world of QRO. You didn't mention your antenna system or band. Common problems guys have: 1) open wire line with goofy unbalanced antenna attached. 2) poor grounding of the rig. (A fat short ground connecting amp and rig needed.) Corroded connections at the ground stake. Old ground stake which has had the copper clad corroded away. 3) no balun or at least a coil of coax at the feedpoint of balanced antennas. The number of turns varies with freq. More turns isn't necessarily better. Unbalanced antennas often need a string of ferrites at the feed point around the coax. 4) tuners trying to tune a too short antenna. 5) indoor antennas or antennas too close to the house. Too bad one can't take a can of aerosol spray, spray the air and see the concentrations of RF. A severe RFI problem appeared over night here once. It turned out that the ground to the xcvr had worked loose with time. Tightening it up solved the problem. If you only operate one band, a 1/4 wave counterpoise connected to the amp may help. Just run it under the rug. Is the computer case grounded? 73 de Brian/K3KO --- In digitalradio@ yahoogroups. com, Rick <[EMAIL PROTECTED]> wrote: > > Until recently, I only ran 100 watts maximum power, but I did purchase > an Ameritron ALS-600 amplifier to help me mostly on lower band SSB. I > was using the rig today and testing out my new Heil 781 mike that I am > using to replace my ICOM hand mike. And we were testing various settings > on the rigs bass and treble transmit controls. > > During the test the other stations suddenly noticed rather severe RFI > feedback. I switched back to the old mike but the problem was still > there. Having had a lot of problems in the past, I knew that this was > likely due to RF getting into my digital control or audio lines from the > computer sound card to the rig. > > Turning off the amplifier did stop the RFI, so it is apparently due to > the increased RF. Also, after unplugging the audio line in and out to > the ICOM 756 Pro 2, which is via a DIN plug on the back of the rig, the > problem went away. Even with the amplifier running at full power. The > CI-V was still connected. > > I still can not explain why no one noticed the problem earlier as they > were critiquing my audio and would have noticed it. > > On both my CI-V and my audio lines I have about 20 turns of the cables > around their own 1/2" x 7" ferrite rod which has a mu of 125. This was > the way that I found would externally remove RF flowing on the outside > of cables. > > For those of you who run power, even if not for digital modes but for > other modes and have the connections left in place on the rig, how are > you able to reduce or eliminate RF feedback in your audio lines? I have > 1:1 transformers in line, no other chokes or bypass capacitors. > > 73, > > Rick, KV9U > __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
[digitalradio] Re: RF feedback with interface
Rick, Your no ground situation + high power is a recipe for RF problems. Try some 1/4 wave counterpoises connected to the rig ground. You can have multiple ones for different bands connected simultaneously. People who live on second and third floors have the same problem with long ground paths. Counterpoises help them sometimes. Cheap and easy. Sounds like you need <10 db of improvement and these may be enough. 73 de Brian/K3KO --- In digitalradio@yahoogroups.com, Jose Amador <[EMAIL PROTECTED]> wrote: > > > Rick, > > Every wire "under the influence" of your radiating antenna can be a > feedback pickup path. > > Try to minimize currents, ferrites are your best friends. Use only > capacitors in shunt to ground > only after a choke to minimize currents. > > All the homebrew equipment I have built has an RF filter in the power > leads, L first and C after. > > I had to wind some ten turns of my speakers power cable on a mid size > toroidal ferrite core > (salvaged fom a defunct 100 W commercial radio) to quiet down the noises > of PSK31 and Olivia. > > In a course of a certain solid state high power broadcast transmitter I > learned that EVERYTHING > that enters the transmitter cabinet passes thru some ferrite core FIRST, > because every wire may > be a feedback path in the near field of the broadcast antenna. It even > provides some lightning > protection, inductors first, varistors after, in the incoming signal path. > > Hope this helps, > > Jose, CO2JA > > Rick escribió: > > > Antenna that gives me the main problem is an inverted vee dipole with > > apex at about 35 feet and ends at about 15 feet high. I have a > > Butternut vertical located about 150 out from the house that does not > > seem to cause any problems, but for close in (< 200 miles) the dipole > > is indispensable. It is of course throwing RF back to the shack as > > the apex is only 40 feet in horizontal distance to the base of the > > tower on the end of the garage. > > > > Everything is coax fed. I have tried "balanced" lines with tuners off > > and on over the years, but it is less convenient for routing and can > > be more of a problem with RF feedback too. I don't use any separate > > grounding and may have to try it as the main RF ingress seems to be > > the audio lines from the computer. > > > > If I disconnect from the computer (even leaving the DIN plug > > connected with the ferrite rod on that line which is a few feet long) > > it seems to clear up. It is only a foot of cable between the sound > > card and my 1:1 isolation transformers. I suspect that if I put a > > scope on the shield from the sound card I won't like what I see. > > > > It would be about 20 feet to run a ground to the outside SPG and I > > have also been skeptical that would help a lot. For some lightning > > protection, I disconnect my rigs from the antenna switch which > > grounds all unused feedlines, but of course, only through their > > shields, but at least it makes them common to each other. I admit > > that for 160/80 and maybe 40 meters, a 20 foot run is not too bad for > > "grounding." > > > > 73, > > > > Rick, KV9U > > > __ > > Participe en Universidad 2008. > 11 al 15 de febrero del 2008. > Palacio de las Convenciones, Ciudad de la Habana, Cuba > http://www.universidad2008.cu >
Re: [digitalradio] Re: RF feedback with interface
Rick, Every wire "under the influence" of your radiating antenna can be a feedback pickup path. Try to minimize currents, ferrites are your best friends. Use only capacitors in shunt to ground only after a choke to minimize currents. All the homebrew equipment I have built has an RF filter in the power leads, L first and C after. I had to wind some ten turns of my speakers power cable on a mid size toroidal ferrite core (salvaged fom a defunct 100 W commercial radio) to quiet down the noises of PSK31 and Olivia. In a course of a certain solid state high power broadcast transmitter I learned that EVERYTHING that enters the transmitter cabinet passes thru some ferrite core FIRST, because every wire may be a feedback path in the near field of the broadcast antenna. It even provides some lightning protection, inductors first, varistors after, in the incoming signal path. Hope this helps, Jose, CO2JA Rick escribió: > Antenna that gives me the main problem is an inverted vee dipole with > apex at about 35 feet and ends at about 15 feet high. I have a > Butternut vertical located about 150 out from the house that does not > seem to cause any problems, but for close in (< 200 miles) the dipole > is indispensable. It is of course throwing RF back to the shack as > the apex is only 40 feet in horizontal distance to the base of the > tower on the end of the garage. > > Everything is coax fed. I have tried "balanced" lines with tuners off > and on over the years, but it is less convenient for routing and can > be more of a problem with RF feedback too. I don't use any separate > grounding and may have to try it as the main RF ingress seems to be > the audio lines from the computer. > > If I disconnect from the computer (even leaving the DIN plug > connected with the ferrite rod on that line which is a few feet long) > it seems to clear up. It is only a foot of cable between the sound > card and my 1:1 isolation transformers. I suspect that if I put a > scope on the shield from the sound card I won't like what I see. > > It would be about 20 feet to run a ground to the outside SPG and I > have also been skeptical that would help a lot. For some lightning > protection, I disconnect my rigs from the antenna switch which > grounds all unused feedlines, but of course, only through their > shields, but at least it makes them common to each other. I admit > that for 160/80 and maybe 40 meters, a 20 foot run is not too bad for > "grounding." > > 73, > > Rick, KV9U __ Participe en Universidad 2008. 11 al 15 de febrero del 2008. Palacio de las Convenciones, Ciudad de la Habana, Cuba http://www.universidad2008.cu
Re: [digitalradio] Re: RF feedback with interface
Antenna that gives me the main problem is an inverted vee dipole with apex at about 35 feet and ends at about 15 feet high. I have a Butternut vertical located about 150 out from the house that does not seem to cause any problems, but for close in (< 200 miles) the dipole is indispensable. It is of course throwing RF back to the shack as the apex is only 40 feet in horizontal distance to the base of the tower on the end of the garage. Everything is coax fed. I have tried "balanced" lines with tuners off and on over the years, but it is less convenient for routing and can be more of a problem with RF feedback too. I don't use any separate grounding and may have to try it as the main RF ingress seems to be the audio lines from the computer. If I disconnect from the computer (even leaving the DIN plug connected with the ferrite rod on that line which is a few feet long) it seems to clear up. It is only a foot of cable between the sound card and my 1:1 isolation transformers. I suspect that if I put a scope on the shield from the sound card I won't like what I see. It would be about 20 feet to run a ground to the outside SPG and I have also been skeptical that would help a lot. For some lightning protection, I disconnect my rigs from the antenna switch which grounds all unused feedlines, but of course, only through their shields, but at least it makes them common to each other. I admit that for 160/80 and maybe 40 meters, a 20 foot run is not too bad for "grounding." 73, Rick, KV9U Brian A wrote: > Rick, > > Welcome to the world of QRO. > > You didn't mention your antenna system or band. Common problems guys > have: > 1) open wire line with goofy unbalanced antenna attached. > 2) poor grounding of the rig. (A fat short ground connecting amp and > rig needed.) Corroded connections at the ground stake. Old ground > stake which has had the copper clad corroded away. > 3) no balun or at least a coil of coax at the feedpoint of balanced > antennas. The number of turns varies with freq. More turns isn't > necessarily better. Unbalanced antennas often need a string of > ferrites at the feed point around the coax. > 4) tuners trying to tune a too short antenna. > 5) indoor antennas or antennas too close to the house. > > Too bad one can't take a can of aerosol spray, spray the air and see > the concentrations of RF. > > A severe RFI problem appeared over night here once. It turned out > that the ground to the xcvr had worked loose with time. Tightening it > up solved the problem. > > If you only operate one band, a 1/4 wave counterpoise connected to the > amp may help. Just run it under the rug. > > Is the computer case grounded? > > 73 de Brian/K3KO > > > --- In digitalradio@yahoogroups.com, Rick <[EMAIL PROTECTED]> wrote: > >> Until recently, I only ran 100 watts maximum power, but I did purchase >> an Ameritron ALS-600 amplifier to help me mostly on lower band SSB. I >> was using the rig today and testing out my new Heil 781 mike that I am >> using to replace my ICOM hand mike. And we were testing various >> > settings > >> on the rigs bass and treble transmit controls. >> >> During the test the other stations suddenly noticed rather severe RFI >> feedback. I switched back to the old mike but the problem was still >> there. Having had a lot of problems in the past, I knew that this was >> likely due to RF getting into my digital control or audio lines from >> > the > >> computer sound card to the rig. >> >> Turning off the amplifier did stop the RFI, so it is apparently due to >> the increased RF. Also, after unplugging the audio line in and out to >> the ICOM 756 Pro 2, which is via a DIN plug on the back of the rig, the >> problem went away. Even with the amplifier running at full power. The >> CI-V was still connected. >> >> I still can not explain why no one noticed the problem earlier as they >> were critiquing my audio and would have noticed it. >> >> On both my CI-V and my audio lines I have about 20 turns of the cables >> around their own 1/2" x 7" ferrite rod which has a mu of 125. This was >> the way that I found would externally remove RF flowing on the outside >> of cables. >> >> For those of you who run power, even if not for digital modes but for >> other modes and have the connections left in place on the rig, how are >> you able to reduce or eliminate RF feedback in your audio lines? I >> > have > >> 1:1 transformers in line, no other chokes or bypass capacitors. >> >> 73, >> >> Rick, KV9U >> >> > > > > > Announce your digital presence via our Interactive Sked Page at > http://www.obriensweb.com/drsked/drsked.php > > Yahoo! Groups Links > > > > > > >
[digitalradio] Re: RF feedback with interface
Rick, Welcome to the world of QRO. You didn't mention your antenna system or band. Common problems guys have: 1) open wire line with goofy unbalanced antenna attached. 2) poor grounding of the rig. (A fat short ground connecting amp and rig needed.) Corroded connections at the ground stake. Old ground stake which has had the copper clad corroded away. 3) no balun or at least a coil of coax at the feedpoint of balanced antennas. The number of turns varies with freq. More turns isn't necessarily better. Unbalanced antennas often need a string of ferrites at the feed point around the coax. 4) tuners trying to tune a too short antenna. 5) indoor antennas or antennas too close to the house. Too bad one can't take a can of aerosol spray, spray the air and see the concentrations of RF. A severe RFI problem appeared over night here once. It turned out that the ground to the xcvr had worked loose with time. Tightening it up solved the problem. If you only operate one band, a 1/4 wave counterpoise connected to the amp may help. Just run it under the rug. Is the computer case grounded? 73 de Brian/K3KO --- In digitalradio@yahoogroups.com, Rick <[EMAIL PROTECTED]> wrote: > > Until recently, I only ran 100 watts maximum power, but I did purchase > an Ameritron ALS-600 amplifier to help me mostly on lower band SSB. I > was using the rig today and testing out my new Heil 781 mike that I am > using to replace my ICOM hand mike. And we were testing various settings > on the rigs bass and treble transmit controls. > > During the test the other stations suddenly noticed rather severe RFI > feedback. I switched back to the old mike but the problem was still > there. Having had a lot of problems in the past, I knew that this was > likely due to RF getting into my digital control or audio lines from the > computer sound card to the rig. > > Turning off the amplifier did stop the RFI, so it is apparently due to > the increased RF. Also, after unplugging the audio line in and out to > the ICOM 756 Pro 2, which is via a DIN plug on the back of the rig, the > problem went away. Even with the amplifier running at full power. The > CI-V was still connected. > > I still can not explain why no one noticed the problem earlier as they > were critiquing my audio and would have noticed it. > > On both my CI-V and my audio lines I have about 20 turns of the cables > around their own 1/2" x 7" ferrite rod which has a mu of 125. This was > the way that I found would externally remove RF flowing on the outside > of cables. > > For those of you who run power, even if not for digital modes but for > other modes and have the connections left in place on the rig, how are > you able to reduce or eliminate RF feedback in your audio lines? I have > 1:1 transformers in line, no other chokes or bypass capacitors. > > 73, > > Rick, KV9U >
