Re: Topband: Reducing Noise in the Shack
On Tuesday 26 June 2012 05:39:27 John Kaufmann wrote: > This report on RFI mitigation may be of interest to folks here: > http://edocs.nps.edu/npspubs/scholarly/TR/2007/NPS-EC-07-002.pdf. It was > done at the Naval Post Graduate School and almost appears to have been > written for ham applications. > > 73, John W1FV > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK John, is the companion document on reducing noise internally at a site also available? (It's mentioned in the document) Thanks, Bob -- Bob Smits Poverty is the worst form of violence Mohandas Gandhi ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
Thanks for the link, John. This is an excellent study that should be read by anyone plagued by noise. Not a single mention of a clamp on ferrite ring however, as this study has to do mainly with power lines and large industrial noise sources. 73, Ken - K4XL On Tue, Jun 26, 2012 at 8:39 AM, John Kaufmann wrote: > This report on RFI mitigation may be of interest to folks here: > http://edocs.nps.edu/npspubs/scholarly/TR/2007/NPS-EC-07-002.pdf. It was > done at the Naval Post Graduate School and almost appears to have been > written for ham applications. > > 73, John W1FV > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > -- Ken - K4XL BoatAnchor Manual Archive BAMA - http://bama.edebris.com ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
This report on RFI mitigation may be of interest to folks here: http://edocs.nps.edu/npspubs/scholarly/TR/2007/NPS-EC-07-002.pdf. It was done at the Naval Post Graduate School and almost appears to have been written for ham applications. 73, John W1FV ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
Hi Jose, You had no problem hearing my 5W signal in the "Summer Stew" and you were the farthest contact made during my limited operating time. Some loud signals could not hear me at all so I figured you probably had an excellent receive system. I enjoyed reading the description of your interference filters. Thanks and Best Regards, Jim / W1FMR --- On Sun, 6/24/12, N4IS wrote: From: N4IS Subject: Re: Topband: Reducing Noise in the Shack To: "'Guy Olinger K2AV'" , "'DAVID CUTHBERT'" Cc: Topband@contesting.com, "'Wayne Willenberg'" Date: Sunday, June 24, 2012, 11:43 AM Hi guys Let me share what I've done about reducing noise in the Shack, not all station has this kind of configuration, you may not need it. 1- Tom is 100% right about common mode noise. I killed all common mode noise outside the Shack. My desk is in the corner of the house and I'm using two steel galvanized box, one for AC with a huge common mode filters made with wire #10 and FT270-31. The second 24x24x8 for the RX and TX cables, all grounded inside. The RX cables have also FT240-31 chokes with RG142 cables. 2- The 220Vac enters the wall and is connect to another filter with very large surge protectors and feed my amplifier. After the filter connected to a large aluminum bar 8"x 1/4"x 72 " followed by an 1 KW isolation steep down transformer to 110Vac. It is important to avoid ground loop using only one point of grounding. 3- EMI/RFI has two components, electrical and magnetic field must be blocked. My RX antennas has low gain and they work near RX noise floor ,that requires a high gain preamp, my preamp has >40 db gain. Aluminum boxes are not enough to kill the magnetic field noise from the PC and from my 2 LDC screen monitors, the solution was steel tinplated 24"x36"galvanized steel plate bellow the desk and to build a large box 20" x 30" x 3" to install all preamps and the RX switches inside. 4- Also there is a long ground #00 cable around the corner of the house with ground rods each 10 FT, one leg is 40Ft log and the other is 60 FT long and connected to the house power meter ground rod. at the end, like NEC requires. That builds a huge low impedance ground protecting the house and the shack. It is a good ground but for protection it is never good enough. If my station has a big secret it is the ground system for sure, one for RF and another for lightening connected together in one point by a large galvanized 4"steel pipe between the box in the house and the box in ta the base of the TX tower 70 FT apart. All my cable runs inside a galvanized steel pipes to cut the magnetic field. I know it is overkill the problem but I'm glad I did it that way. Regards Jose Carlos N4IS ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
> 3- EMI/RFI has two components, electrical and magnetic field must be > blocked. My RX antennas has low gain and they work near RX noise floor > ,that > requires a high gain preamp, my preamp has >40 db gain. Aluminum boxes > are > not enough to kill the magnetic field noise from the PC and from my 2 LDC > screen monitors, the solution was steel tinplated 24"x36"galvanized steel > plate bellow the desk and to build a large box 20" x 30" x 3" to install > all preamps and the RX switches inside. While this does exist at frequencies below where skin depth in shields occurs, the "magnetic field thing" is a very common myth, or misconception, with radio frequency signals. A monitor with low frequency energy or transformer might be able to induce very low frequency signals across a thin shield, and they might get into circuits sensitive to low frequencies, but this takes special errors. This is why audio system behavior cannot be applied to RF systems. If we look at the thin copper sheet on this page: http://www.w8ji.com/skindepth.htm we see nothing penetrates the wall, once it is several skin-depths thick. Neither magnetic nor electric fields will penetrate any shield or wall more than several skin depths thick, no matter what conductive material the shield or wall is made from. This is why the foil layer on CATV cable is so effective. While a braid weaves in and out, and current from the outer wall can weave in and out once the braid tarnishes or becomes "unpacked", it doesn't matter how "dirty" a solid wall becomes. All we need is good electrical integrity to the connector shell at each end, many skin depths of thickness, and the shield system is very effective. This is also why metal boxes with properly mounted connectors are necessary in high noise environments, although a proper groundplane (with properly mounted connectors) can be almost as effective. My antenna distribution and group system switching system is an open groundplane construction, and has no measureable noise ingress. http://www.w8ji.com/images/New%20Contest%20Room/Contest%20station%20CQWW2007/receiver-switch-matrix.jpg Note the connectors are not mounted on plastic with grounding leads entering the area of electronics, but are mounted on the groundplane formed by the 5-sided box that houses the amplifiers and relays. The groundplane prevents common mode from exciting the internal point-to-point wiring, so I can use twisted-pair enamel wiring inside the matrix for space and speed. What goes through the shield of a shielded loop antenna? Nothing at all, not the magnetic or electric fields. The shield is the actual antenna, and it couples to the inner conductor via the voltage across the gap. That's why a "shielded loop" has to have perfect shield symmetry, or it has common mode issues. If you install a device built with a plastic box, especially without a solid groundplane, it is guaranteed to have common mode issues. On the other hand even an open housing (like I use in my switching matrix) is OK, if the backplane has integrity and the connectors mount properly. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
Hi guys Let me share what I've done about reducing noise in the Shack, not all station has this kind of configuration, you may not need it. 1- Tom is 100% right about common mode noise. I killed all common mode noise outside the Shack. My desk is in the corner of the house and I'm using two steel galvanized box, one for AC with a huge common mode filters made with wire #10 and FT270-31. The second 24x24x8 for the RX and TX cables, all grounded inside. The RX cables have also FT240-31 chokes with RG142 cables. 2- The 220Vac enters the wall and is connect to another filter with very large surge protectors and feed my amplifier. After the filter connected to a large aluminum bar 8"x 1/4"x 72 " followed by an 1 KW isolation steep down transformer to 110Vac. It is important to avoid ground loop using only one point of grounding. 3- EMI/RFI has two components, electrical and magnetic field must be blocked. My RX antennas has low gain and they work near RX noise floor ,that requires a high gain preamp, my preamp has >40 db gain. Aluminum boxes are not enough to kill the magnetic field noise from the PC and from my 2 LDC screen monitors, the solution was steel tinplated 24"x36"galvanized steel plate bellow the desk and to build a large box 20" x 30" x 3" to install all preamps and the RX switches inside. 4- Also there is a long ground #00 cable around the corner of the house with ground rods each 10 FT, one leg is 40Ft log and the other is 60 FT long and connected to the house power meter ground rod. at the end, like NEC requires. That builds a huge low impedance ground protecting the house and the shack. It is a good ground but for protection it is never good enough. If my station has a big secret it is the ground system for sure, one for RF and another for lightening connected together in one point by a large galvanized 4"steel pipe between the box in the house and the box in ta the base of the TX tower 70 FT apart. All my cable runs inside a galvanized steel pipes to cut the magnetic field. I know it is overkill the problem but I'm glad I did it that way. Regards Jose Carlos N4IS ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
Differential mode filtering goes inside the outlet strip and ferrites on the outside take care of common mode on my filters. Ferrites can be externally added to any DM only filter. Carl KM1H - Original Message - From: "Guy Olinger K2AV" To: "DAVID CUTHBERT" Cc: ; "Wayne Willenberg" Sent: Thursday, June 21, 2012 3:07 PM Subject: Re: Topband: Reducing Noise in the Shack > On Thu, Jun 21, 2012 at 2:59 PM, DAVID CUTHBERT > wrote: > >> The W7NQN line filter is a differential-mode filter. You need a filter >> that >> is designed for common-mode filtering. >> >> Dave WX7G > > > This is from the web page advertisement: > - > Compare this with a Brand "C" filter which only handles common-mode > interference problems. The NQN AC power-line filters are optimized for > common-mode and differential-mode filtering and have about 3 times the > components of brand "C". > - > > Seems to specifically include common mode. > > See http://arraysolutions.com/Products/nqnaclinefilter.htm > > 73, Guy. > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > - > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1424 / Virus Database: 2433/5083 - Release Date: 06/21/12 > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
I'd take that question to the seller for an explanation. The filter may be intended to quiet a particular noisy device, like a PC. It only needs to be rated for the current drawn if it's on the customer side of the power outlet. Otherwise all our lamps would have to have #12 zip cord, and all extension cords would have to be #12. And fuses are not required in extension cords or lamp cords clearly unsafe with an actual 15 or 20 amps on it. 73, Guy. On Thu, Jun 21, 2012 at 4:28 PM, DAVID CUTHBERT wrote: > I don't like diff mode only filters because they have diff mode to common > mode conversion due to component tolerance. > > I don't see a fuse in the NQN filter and it us rated for only 7 amps. To > be used on a 20 amp circuit without an internal fuse it must be able to > handle 20 amps. I assume it's not UL listed? > > Dave WX7G > On Jun 21, 2012 1:07 PM, "Guy Olinger K2AV" wrote: > >> On Thu, Jun 21, 2012 at 2:59 PM, DAVID CUTHBERT >> wrote: >> >>> The W7NQN line filter is a differential-mode filter. You need a filter >>> that >>> is designed for common-mode filtering. >>> >>> Dave WX7G >> >> >> This is from the web page advertisement: >> - >> Compare this with a Brand "C" filter which only handles common-mode >> interference problems. The NQN AC power-line filters are optimized for >> common-mode and differential-mode filtering and have about 3 times the >> components of brand "C". >> - >> >> Seems to specifically include common mode. >> >> See http://arraysolutions.com/Products/nqnaclinefilter.htm >> >> 73, Guy. >> > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
I don't like diff mode only filters because they have diff mode to common mode conversion due to component tolerance. I don't see a fuse in the NQN filter and it us rated for only 7 amps. To be used on a 20 amp circuit without an internal fuse it must be able to handle 20 amps. I assume it's not UL listed? Dave WX7G On Jun 21, 2012 1:07 PM, "Guy Olinger K2AV" wrote: > On Thu, Jun 21, 2012 at 2:59 PM, DAVID CUTHBERT wrote: > >> The W7NQN line filter is a differential-mode filter. You need a filter >> that >> is designed for common-mode filtering. >> >> Dave WX7G > > > This is from the web page advertisement: > - > Compare this with a Brand "C" filter which only handles common-mode > interference problems. The NQN AC power-line filters are optimized for > common-mode and differential-mode filtering and have about 3 times the > components of brand "C". > - > > Seems to specifically include common mode. > > See http://arraysolutions.com/Products/nqnaclinefilter.htm > > 73, Guy. > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
White papers: http://docs.commscope.com/Public/Coax101.pdf Although the test frequency and method is not described, this shows the difference between Quad shield and single foil and braid is 7 dB before 10,000 flexes and 13 dB after 10,000 flexes. My measurements of F11 are at: http://www.w8ji.com/coaxial_cable_leakage.htm Those measurements were made in 2007, and repeated in 2011 with no definate change in results. That cable has crimped connectors. Another white paper, which bears out measurements: http://www.westpenn-wpw.com/pdfs/coax_construction.pdf 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
Dear Topbanders, I use an ICE Model 475-3 AC Line filter in the shack. It provides inductive isolation, overvoltage control, capacitive decoupling and interference control of both common mode and differential mode signals. It will handle 25 amp at 110 VAC. Usually across the line capacitors are used to suppress differential mode noise (usually termed X-capacitors). And, too, common mode choke coils are used to suppress common mode noise (in series); line bypass capacitors (Y-capacitors) supress common mode noise. This unit really works. 73, John, W4NU On 6/21/2012 3:07 PM, Guy Olinger K2AV wrote: > On Thu, Jun 21, 2012 at 2:59 PM, DAVID CUTHBERT wrote: > >> The W7NQN line filter is a differential-mode filter. You need a filter that >> is designed for common-mode filtering. >> >> Dave WX7G > > This is from the web page advertisement: > - > Compare this with a Brand "C" filter which only handles common-mode > interference problems. The NQN AC power-line filters are optimized for > common-mode and differential-mode filtering and have about 3 times the > components of brand "C". > - > > Seems to specifically include common mode. > > See http://arraysolutions.com/Products/nqnaclinefilter.htm > > 73, Guy. > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
On Thu, Jun 21, 2012 at 2:59 PM, DAVID CUTHBERT wrote: > The W7NQN line filter is a differential-mode filter. You need a filter that > is designed for common-mode filtering. > > Dave WX7G This is from the web page advertisement: - Compare this with a Brand "C" filter which only handles common-mode interference problems. The NQN AC power-line filters are optimized for common-mode and differential-mode filtering and have about 3 times the components of brand "C". - Seems to specifically include common mode. See http://arraysolutions.com/Products/nqnaclinefilter.htm 73, Guy. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
The W7NQN line filter is a differential-mode filter. You need a filter that is designed for common-mode filtering. Dave WX7G On Jun 21, 2012 10:32 AM, "Wayne Willenberg" wrote: > As I mentioned in a post a few days ago, I am at the very beginning of > being able to operate on 160 and 80M’s. (To date, I have only operated on > 10, 15 and 20M.) I have been doing a lot of reading, primarily ON4UN’s > “Low-Band DXing.” > > > My rig (FT-dx5000) is located on a desk. Immediately under the desk is my > computer, and just above the rig is a shelf on which sits 2 flat-screen > monitors. > > > One of the points made in “Low-Band DXing” is the necessity of reducing > noise in the shack. The author states at page 7-75: “It is essential to > feed the equipment at the shack through high-quality mains filters.” In > looking for such filters, I have come across the W3NQN AC Line Filter. It > seems to be built with quality components, but I have not been able to find > any specs on the amount of attenuation it provides to EMI and RFI noise at > various frequencies (either common or differential mode). Could someone > recommend a “high-quality mains filter” or comment on the W3NQN filter? > > > The author goes on to state: “The bottom side of the operating table in my > shack is completely covered with aluminum sheet. This represents a lot of > capacitance and virtually zero inductance, which is just what you want! > Quality mains filters are bolted directly to those sheets and the mains > outlet to which the equipment is connected is connected as well. The > ground plane is connected with very short low-inductance wide straps to > long copper ground rods.” Would someone please explain to me the purpose > of this ground plane and how it helps reduce noise? How does “a lot of > capacitance and virtually zero inductance” under a transceiver help reduce > noise? > > > Thanks in advance for advice and help for a newcomer. > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
You can build many excellent line filters for the cost of one of anything from DXE, etc. I build mine into the older style USA made outlet strips using standard ferrite rods, and AC rated disc caps with a 3dB cuttoff of 100KHz. Listening on any frequency on a TS-940 and TS-950SD without an antenna there is absolutely no noise above about 400 KHz and it shows up below that but is well below antenna noise for most of the way down in frequency. Carl KM1H - Original Message - From: "Wayne Willenberg" To: Sent: Thursday, June 21, 2012 12:32 PM Subject: Topband: Reducing Noise in the Shack As I mentioned in a post a few days ago, I am at the very beginning of being able to operate on 160 and 80M’s. (To date, I have only operated on 10, 15 and 20M.) I have been doing a lot of reading, primarily ON4UN’s “Low-Band DXing.” My rig (FT-dx5000) is located on a desk. Immediately under the desk is my computer, and just above the rig is a shelf on which sits 2 flat-screen monitors. One of the points made in “Low-Band DXing” is the necessity of reducing noise in the shack. The author states at page 7-75: “It is essential to feed the equipment at the shack through high-quality mains filters.” In looking for such filters, I have come across the W3NQN AC Line Filter. It seems to be built with quality components, but I have not been able to find any specs on the amount of attenuation it provides to EMI and RFI noise at various frequencies (either common or differential mode). Could someone recommend a “high-quality mains filter” or comment on the W3NQN filter? The author goes on to state: “The bottom side of the operating table in my shack is completely covered with aluminum sheet. This represents a lot of capacitance and virtually zero inductance, which is just what you want! Quality mains filters are bolted directly to those sheets and the mains outlet to which the equipment is connected is connected as well. The ground plane is connected with very short low-inductance wide straps to long copper ground rods.” Would someone please explain to me the purpose of this ground plane and how it helps reduce noise? How does “a lot of capacitance and virtually zero inductance” under a transceiver help reduce noise? Thanks in advance for advice and help for a newcomer. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1424 / Virus Database: 2433/5083 - Release Date: 06/21/12 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
My rig (FT-dx5000) is located on a desk. Immediately under the desk is my computer, and just above the rig is a shelf on which sits 2 flat-screen monitors. One of the points made in “Low-Band DXing” is the necessity of reducing noise in the shack. The author states at page 7-75: “It is essential to feed the equipment at the shack through high-quality mains filters.” In looking for such filters, I have come across the W3NQN AC Line Filter. It seems to be built with quality components, but I have not been able to find any specs on the amount of attenuation it provides to EMI and RFI noise at various frequencies (either common or differential mode). Could someone recommend a “high-quality mains filter” or comment on the W3NQN filter? I'd worry about that later, and if I needed filters, I'd filter at the noise source. Unless you look at a Star Roamer or some other vacuum tube vintage receiver, you'll find most radios are extremely good for internal shielding of mains or power supply leads to the receiver RF system. In my experience, most leakage problems are in marginal shield grounding connections in phono plugs or poor external equipment design, and not in radios at all. For example, plastic boxes with wires for jack ground leads inside are hundreds or thousands of times worse than anything getting into the radio. When external connections are cleaned up, with any modern solid state radio I have owned or used, the issue becomes devices radiating out to antennas, which then pick up the noise. I had a particularly difficult computer supply. Rather than do extraordinary and difficult things to a dozen points in the RX system, and move my antennas further away from the house, I cleaned up that supply with a filter. A normal station with proper attention to common mode suppression on feedlines at the antenna, and good connections on shields, should not even need a desk ground. (One exception might be power line safety. My old two-wire tube gear, like my Ranger II and HQ-120, has safety grounded cabinets.) Would someone please explain to me the purpose of this ground plane and how it helps reduce noise? How does “a lot of capacitance and virtually zero inductance” under a transceiver help reduce noise?>>> The only cases I can think of, where a large desk groundplane might reduce noise, are if: 1.) The antenna has significant common mode current that makes it all the way into the house. For example, look at a longwire shack ground. An end fed longwire antenna is a system with terrible common mode, as are "end-fed dipoles". http://www.w8ji.com/long_wire_antenna.htm 2.) There are poorly constructed 'boxes" in the receive path. The groundplane and shield path integrity in receiving paths is critical. 3.) Internal shack cables have poor shield connections. 4.) Some device in the shack, or near the shack, is exciting terrible common mode RF currents on wiring. Personally, I'd never bother with an extraordinary desk ground. I'd fix the real problem or problems. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: Reducing Noise in the Shack
As I mentioned in a post a few days ago, I am at the very beginning of being able to operate on 160 and 80M’s. (To date, I have only operated on 10, 15 and 20M.) I have been doing a lot of reading, primarily ON4UN’s “Low-Band DXing.” My rig (FT-dx5000) is located on a desk. Immediately under the desk is my computer, and just above the rig is a shelf on which sits 2 flat-screen monitors. One of the points made in “Low-Band DXing” is the necessity of reducing noise in the shack. The author states at page 7-75: “It is essential to feed the equipment at the shack through high-quality mains filters.” In looking for such filters, I have come across the W3NQN AC Line Filter. It seems to be built with quality components, but I have not been able to find any specs on the amount of attenuation it provides to EMI and RFI noise at various frequencies (either common or differential mode). Could someone recommend a “high-quality mains filter” or comment on the W3NQN filter? The author goes on to state: “The bottom side of the operating table in my shack is completely covered with aluminum sheet. This represents a lot of capacitance and virtually zero inductance, which is just what you want! Quality mains filters are bolted directly to those sheets and the mains outlet to which the equipment is connected is connected as well. The ground plane is connected with very short low-inductance wide straps to long copper ground rods.” Would someone please explain to me the purpose of this ground plane and how it helps reduce noise? How does “a lot of capacitance and virtually zero inductance” under a transceiver help reduce noise? Thanks in advance for advice and help for a newcomer. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
