Re: Topband: Elimination of Treadmill RFI on 160 meters
Data from another treadmill RFI success story. A few days ago Lionel (N5LB) added filters to his treadmill based on what I had done to eliminate RFI from my wife's treadmill, and below are his very successful results. Don I want to tell you my results with the treadmill and the delta filter. Before the filter: 160m - 91 dbm 80m -77 dbm 40m -97 dbm 20m -93 dbm 15m -97 dbm 12m -110 dbm 10m nil After the Delta install 160, 80, 40, 20 m below the mds at - 131 dbm 15, 12m -110 dbm After adding a FT240-61 with 7 turns of #12 stranded in the line side of the Delta. 160 - 10m not measurable, mds is ~ -131dbm. Not visible on Flex 5000 waterfall. All of the dbm readings are from the Flex 5000 meter. S7 = ~ -90 dbm so the RFI was really bad. So like you case I needed additional filtering. For me it was higher in frequency so the Delta attenuation must drop off above 20m. I was able to fit the Delta and the toroid inside of the treadmill motor and control housing making for a neat install. Thanks for the excellent suggestions. I bought the Delta from Digikey and had it 36 hours later, incredible service. Lionel Note that Lionel used the same Delta Filter that I used (model : 20DRGG5). He used an FT240-61 core which he had on hand with 7 turns of the Hot and Neutral wires passing through the core (ground wire die not pass through his core) whereas I used 14 turns of the power cord on a 2.4 OD Fair-Rite #31 mix toroid core (Neutral, Hot, and Ground wires passing through the core). Just FYI, and glad to hear others are having success using filters on their treadmill similar to what I used which have provided excellent results. 73, Don (wd8dsb) _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Elimination of Treadmill RFI on 160 meters
Bifilar winding of power leads is a two edged sword. While it reduces core flux from power line currents, it also reduces differential suppression in a similar fashion. In a tightly coupled choke, the windings simply behave like a transmission line. It takes a stand-alone choke in each conductor to add significant differential mode impedances, or a poorly coupled common core choke. You will not obtain that with a bifilar or trifilar winding. For a long time, Corcom has recognized this for use in their power-entry EMI/RFI filters. Their high-performance line filters use a combination of common-mode and differential-mode components. In the link below, note the use of additional DM filtering in their FC10 product. The FC10B model uses identical CM filtering but lesser differential mode filtering at a reduced price. These filters will typically cure most any junk that appears on AC lines of modern household appliances, including switched variable-speed motor drives. http://www.mouser.com/ds/2/418/NG_CS_1654001_CORCOM_PRODUCT_GUIDE_FC_SERIES_0611-370733.pdf Paul, W9AC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
On Sat,1/31/2015 5:48 AM, Paul Christensen wrote: For a long time, Corcom has recognized this for use in their power-entry EMI/RFI filters. Their high-performance line filters use a combination of common-mode and differential-mode components. In name only. As Tom noted earlier, AC line filters do NOTHING to the Green wire -- it goes right through them. What the power industry calls common mode is voltage between neutral and Green. That's NOT common mode as the rest of the world would define it. On Sat,1/31/2015 6:58 AM, Jim Garland wrote: We're just making the point that a common mode choke's effectiveness in blocking common mode currents depends on the impedance to GROUND of the termination of the conductors. I used a parallel line in my example merely to illustrate the point, since current flow in e.g., coax cable. On Sat,1/31/2015 6:58 AM, Jim Garland wrote: We're just making the point that a common mode choke's effectiveness in blocking common mode currents depends on the impedance to GROUND of the termination of the conductors. Not the impedance to GROUND, but the impedance of the common mode circuit as an antenna. I used a parallel line in my example merely to illustrate the point, since current flow in e.g., coax cable. An antenna doesn't have to be grounded to carry RF current and radiate it. As the extreme case, consider, for example, your parallel wire line that is a half wavelength long (free space). It's a near ideal length, and will radiate a lot of signal if the antenna puts common mode current on it. A ham talkie has no connection to earth, but the chassis and the capacity-coupled body of the person holding it provides enough of a counterpoise for it to work. Likewise, a quarter-wave whip on a vehicle has no connection to earth, but the vehicle's frame provides the counterpoise (if we manage to remove or bypass the paint that prevents sections of it from making contact). A common mode choke of the sort I've recommended (and measured) is, by definition, a brute force solution. Yes, the extent to which it reduces radiation from the unintentional antenna will be very dependent on the impedance of the common mode circuit and the effectiveness of those unintentional antennas as radiators. I've looked at it in NEC models with best and worst cases of feedline length with half-wave dipole fed varying degrees of off center, for example. But if the noise source is strong, and/or if the noise source is close enough to us, antennas don't have to be ideal to give us a lot of grief. The first work I did on this was around 2003, in Chicago, and the first noise sources I tackled were the wired Ethernet switch and computers connected to it. I made a pretty good dent in the birdies that I heard in my HF RX by winding 5-7 turns of the CAT5 through a #43 Fair-Rite toroid (I didn't yet have #31). But it made no dent at all in the broadband noise I heard on 2M from those cables. But the reason I was looking at this in the first place was that I was hearing lots of anecdotal reports of RFI to church sound systems from stations on the high end of the AM broadcast band, and wanted to both understand the causes and develop a fix. The SCIN paper that I referenced to you yesterday showed one of the causes. Another paper documented the Pin One Problem as part of the cause. Both causes were related to shield current on shielded twisted pair cables. The multi-pair mic cables running through a wood-frame church make great RX antennas on the broadcast band, and the otherwise very nice Mackie mixers not only had Pin One Problems at their mic inputs, but also had response from DC to daylight in the name of good audio phase response. When I swept 2 MHz into their inputs, I got 2 MHz at their outputs! In a field test across the road from WGN (50kW) 14 turns of the mic cable around a #43 2.4-in o.d. toroid killed the RFI. As I learned later when I studied chokes in detail, this wasn't even an ideal choke, but it was good enough. This was 2001-2005, and after I very seriously beat them up, Mackie redesigned their mixers to correct these issues. Obviously a parallel line not terminated in anything will have no common mode current because there's no place for the current to go. Introducing choke coupling and stray capacitance, Q, resonances, etc., into the discussion, while obviously important in real life, tend to obscure the basics. Not true -- indeed, a common mode choke is most effective BECAUSE OF the high resistance around resonance that RESULTS from its own stray capacitance. And because it's a very low Q resonance (typically 0.4), it's quite broad. The virtue of #31 material is that there are TWO resonances -- the resonance of the coil, and the dimensional resonance of the core. This is discussed in my tutorial. Dimensional resonance is discussed in detail in the first Snelling book, which is also referenced. 73, Jim K9YC
Re: Topband: Elimination of Treadmill RFI on 160 meters
Tom, You simply don't get it. The choke is NOT a filter. It is a high impedance added to the common mode circuit. The common mode circuit is acting as an ANTENNA, either for RX or TX. If for TX, the noise source is inside the box, and the current will depend upon the voltage of the source and behavior of the circuit as an antenna. If for RX (that is, the noise is received on the wiring by simple antenna action and coupled into the box via failure of the wiring to go the shielding enclosure) the current will again depend upon the behavior of the circuit as an RX antenna. When we add a choke of sufficiently high resistive impedance to that circuit, we reduce the current at frequencies where the choke is effective. When preparing to publish my first research on this in 2003 (to the AES), I found references in ancient applications notes from EU mfrs of ferrites showing that they clearly understood this principle. Those ferrite cores molded onto cables emerging from electronic equipment are not filters, they are chokes. They do work in the frequency for which they are designed, and the only capacitance in the circuit is their own parallel capacitance that forms their resonant circuit -- it is the capacitance from one end of the core to the other via the dielectric of the core. 73, Jim K9YC On Fri,1/30/2015 3:16 AM, Tom W8JI wrote: Any filtering or decoupling system works by the ratio of series impedance to shunt impedances. A series choke is useless unless there is some value of shunt impedance in the system. As a matter of fact, lack of established shunt impedances is what can drive choke requirements to unrealistic values. This is true in baluns, just like it is in line filters. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
On Fri,1/30/2015 2:49 PM, Jim Garland wrote: But, like I said, maybe I'm not following something. Right -- you are not. First, you don't understand what common mode is. Second, you don't understand the choke. A ferrite common mode choke STARTS OUT as a lossy inductor, but one with shunt capacitance. This forms a very low Q resonant circuit (typically 0.4), and thus a very broad resonant peak. It is the resistance around resonance that forms an effective common mode choke. I've discussed this in considerable detail in tutorial form in k9yc.com/RFI-Ham.pdf and some of that material has been added to the ARRL Handbook. There's also a pdf of the slides that go with an RFI tutorial that I've done for several ham clubs. It's on my website -- k9yc.com/publish.htm I suggest that you study these two pieces. It's far too much work (and probably boring for many readers of this list) for me to post it here. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
Guys, I'm not following all this, possibly because I'm confused by Jim's distinction between filters and chokes, because in both cases they're just lossy inductors, although used in different ways and for different purposes. Consider common mode noise on a simple parallel wire transmission line. Identical in-phase noise currents would flow on each of the parallel wires. A common mode choke around the line would insert a high impedance equally onto both wires.The choke's effectiveness at suppressing the common mode currents would depend on the shunt impedance to ground of the two wires. The shunt impedance between the two wires e.g., the impedance of the transmission line, is immaterial since there is no common mode voltage difference between them. On the other hand, the choke's ability to shield differential (as opposed to common mode) currents depends a great deal on the differential shunt impedance. The lower the shunt impedance, the more effective the choke. Seems to me this is quite apparent if one draws out the circuit and includes both the impedances to ground and the differential impedance beteeen the two wires. But, like I said, maybe I'm not following something. 73, Jim W8ZR -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Jim Brown Sent: Friday, January 30, 2015 2:27 PM To: topband@contesting.com Subject: Re: Topband: Elimination of Treadmill RFI on 160 meters Tom, You simply don't get it. The choke is NOT a filter. It is a high impedance added to the common mode circuit. The common mode circuit is acting as an ANTENNA, either for RX or TX. If for TX, the noise source is inside the box, and the current will depend upon the voltage of the source and behavior of the circuit as an antenna. If for RX (that is, the noise is received on the wiring by simple antenna action and coupled into the box via failure of the wiring to go the shielding enclosure) the current will again depend upon the behavior of the circuit as an RX antenna. When we add a choke of sufficiently high resistive impedance to that circuit, we reduce the current at frequencies where the choke is effective. When preparing to publish my first research on this in 2003 (to the AES), I found references in ancient applications notes from EU mfrs of ferrites showing that they clearly understood this principle. Those ferrite cores molded onto cables emerging from electronic equipment are not filters, they are chokes. They do work in the frequency for which they are designed, and the only capacitance in the circuit is their own parallel capacitance that forms their resonant circuit -- it is the capacitance from one end of the core to the other via the dielectric of the core. 73, Jim K9YC On Fri,1/30/2015 3:16 AM, Tom W8JI wrote: Any filtering or decoupling system works by the ratio of series impedance to shunt impedances. A series choke is useless unless there is some value of shunt impedance in the system. As a matter of fact, lack of established shunt impedances is what can drive choke requirements to unrealistic values. This is true in baluns, just like it is in line filters. _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
Consider common mode noise on a simple parallel wire transmission line. Identical in-phase noise currents would flow on each of the parallel wires. A common mode choke around the line would insert a high impedance equally onto both wires.The choke's effectiveness at suppressing the common mode currents would depend on the shunt impedance to ground of the two wires. The shunt impedance between the two wires e.g., the impedance of the transmission line, is immaterial since there is no common mode voltage difference between them. On the other hand, the choke's ability to shield differential (as opposed to common mode) currents depends a great deal on the differential shunt impedance. The lower the shunt impedance, the more effective the choke. Seems to me this is quite apparent if one draws out the circuit and includes both the impedances to ground and the differential impedance between the two wires. But, like I said, maybe I'm not following something. Differential current suppression is a pretty complex function in a bifilar or trifilar choke, because mutual coupling between conductors enters the equation. Bifilar winding of power leads is a two edged sword. While it reduces core flux from power line currents, it also reduces differential suppression in a similar fashion. In a tightly coupled choke, the windings simply behave like a transmission line. It takes a stand-alone choke in each conductor to add significant differential mode impedances, or a poorly coupled common core choke. You will not obtain that with a bifilar or trifilar winding. All of these problems, regardless of strong opinions, translate to ratios of shunt impedances and series impedances. They are nothing more than pi-attenuators, or pi-filters. If impedances loading a choke on either or both ends are very high, attenuation is significantly reduced. We can see this with choke baluns. If a choke balun is placed where the antenna sources very high common mode voltages (high impedance), choking impedance often has to reach impractical levels. The same is true for the load side of the choke. As you say ZR, it is all about all of the impedances. It is a system, and looking at one part in isolation is pointless. I keep bringing up a CATV system I had to cure for BCI. An apartment complex was constructed right over the radial system of a 5 kW AM station. The cable TV company tried triple shielded cables, and regular common mode chokes. They also tried CATV high pass filters. None of it worked, the system was mess. All I did was have the special cables removed, and standard cables installed. All filters and chokes were removed. The cable entering each building entered alongside power mains, and the shield was bonded to the mains ground. The cable followed the power distribution to each apartment. Inside the apartment, the CATV wall plate was commoned with the safety ground of the wall outlet for the TV set though a suitable rating capacitor. Nearly every apartment cleaned up completely without using a single choke or filter. This was because there was no differential RF allowed between the CATV and the mains. The common mode of the TV, since it was very high at 1520 kHz, prevented significant common mode to the set. A CM choke simply would not have done anything, because the TV's were already electrically small and had a pretty high CM impedance. I have minimal CM choking here. I have no RFI issues, even beaming the four square through the house (just 75-150 feet away). This is because I don't allow differential between wires and cables by use of outlet strips that tie the MATV antenna and other things to the power feeds at each hub. When I do need a choke, it isn't an astronomical value or difficult design. Just a snap on will often be enough, because the shunting impedances are kept low. What works for ingress also works for egress. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
This snide remark ignores the fact that it is generally not practical (nor is it good politics) to go inside your neighbor's equipment to add bypass capacitors. Nor is it practical to open up a wall wart, nor even most consumer equipment. It also ignores the fact that much of RFI at HF is common mode, not differential mode, caused by bonding failures (the Pin One Problem and its power systems equivalent). And it ignores the fact that it is often the cable shield or the power system equipment ground that is carrying the RF noise current, for reasons noted in my earlier post. It isn't a snide remark, it is how we focus on chokes. Any filtering or decoupling system works by the ratio of series impedance to shunt impedances. A series choke is useless unless there is some value of shunt impedance in the system. As a matter of fact, lack of established shunt impedances is what can drive choke requirements to unrealistic values. This is true in baluns, just like it is in line filters. Most outlet strips and devices have room inside for several UL/CSA/ VDE approved bypass capacitors. Rather than paying $30 or much more for some capacitors in a physically large filter can, with minimal choke impedance inside, one might consider a few well-spent dollars for external components. Many times RFI is cured simply by bypassing and closing a loop through a device, where choke requirements alone would be astronomical or ineffective. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
Nice to hear all the comments, recommendations, and indeed some success stories here. I too have a treadmill problem. Although I'm blessed with a radio-friendly spouse who always asks before she starts it up, I'd like to add a line filter. Ferrites on the cord don't by themselves squelch it. Murphy dictates that the new one will show up when she's in the middle of her workout. How about some outlet box recommendations? The electrics are not the hard part for me, it's the mechanics. I've been looking for a suitable box to mount it all in and coming up kind of dry. Maybe I'm not looking for the right keywords. Seems simple, a box with a cutout for two 120VAC outlets and enough room inside for a line filter and some toroids. A strain relief clamp would be a big plus but something else can always be worked out for that. In the past I've bolted a surface mount outlet box to another project box but it's kinda big and ugly, and more expensive than it ought to be. 73 and thanks in advance, Carl WS7L _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
A deep 4 inch box? Add extension rings if necessary? Ganged outlet boxes? http://www.mcmaster.com/#standard-outlet-boxes/=vohae8 I know I've seen on the web somewhere, a Grow-Light filter with 3 big 2.4 toroids all in a 4 inch box. I don't think there was any room left for outlets. I use 4 inch boxes for all sorts of ham accessories (having nothing to do with 120VAC power). They are nice and heavy and stay put. The 3/8 BX clamps work great for cable strain relief. If the treadmill manufacturer had just included 15 cents of waveshaping at the MOSFET, all the external filtering would be completely unnecessary. Tim N3QE On Thu, Jan 29, 2015 at 1:23 PM, Carl Clawson clawso...@gmail.com wrote: Nice to hear all the comments, recommendations, and indeed some success stories here. I too have a treadmill problem. Although I'm blessed with a radio-friendly spouse who always asks before she starts it up, I'd like to add a line filter. Ferrites on the cord don't by themselves squelch it. Murphy dictates that the new one will show up when she's in the middle of her workout. How about some outlet box recommendations? The electrics are not the hard part for me, it's the mechanics. I've been looking for a suitable box to mount it all in and coming up kind of dry. Maybe I'm not looking for the right keywords. Seems simple, a box with a cutout for two 120VAC outlets and enough room inside for a line filter and some toroids. A strain relief clamp would be a big plus but something else can always be worked out for that. In the past I've bolted a surface mount outlet box to another project box but it's kinda big and ugly, and more expensive than it ought to be. 73 and thanks in advance, Carl WS7L _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
If you're trying to find a suitable box to mount *in the wall* that will fit two duplex receptacles and some filters, try a 4-11 box (4-11/16 square) that is 2-1/8 deep (this is a standard size). You can use a plaster ring on this box to allow two duplex receptacles to mount properly and then mount the box in the wall (this last part will be a bit tricky since the 4-11 boxes don't usually have mounting wings). You could also get a double duplex raised cover for the 4-11 box if you want to mount the box on the surface. Any of the electrical supply houses should have all this stuff, just ask for a four eleven box. You might need to ask for a deep box (which is the 2-1/8 version) since there is also a shallow box around 1-1/4 deep. The 4-11 boxes can take any standard clamps that normal electrical boxes take. With the raised cover option you could make a kind of filter cord. Use the raised cover on the 4-11 box. The raised cover adds about 1/2 so that most of the internal space in the 4-11 box would be available for filter components without interference from the receptacles. Ideally you'd use a cable gland (sometimes also called a rubber cord grip) to bring flexible power cable into the box (like type SJ cable). The cable gland is a round fitting with a big tapered rubber grommet inside. When you screw the metal ring over the grommet, the grommet inside compresses in the tapered fitting to grip the cord all the way around. It's much better than any of the metal clamps that are intended for NM cable (Romex). If you want a REALLY strong grip to the cable you can use a kellums grip (a wire basket that works like the Chinese handcuffs that grab fingers), but that's really not necessary. Any of this stuff is available from commercial electrical supply houses but probably not the big box stores. The wholesalers will usually sell to anyone as long as you're friendly and don't ask lots of crazy questions since they don't want to take time to explain things to non-professionals. Just ask for the following items: Four-eleven deep box Double duplex raised cover for the four eleven box Cable gland for 14/3 SJ (or whatever cable you're using) Lock nut for the cable gland (they usually don't include one) Get a few spec-grade receptacles -- they're good and only a few bucks at the supply houses. NEMA number 5-15R is the regular one, 5-20R is the 20 amp version with a T shaped slot. If you need even more room, I'd use a 6x6x4 PVC junction box and mount the receptacles on the blank cover using a normal flush wall plate. This would give you a LOT of room inside, but you'll need to cut your own holes for a cable gland as well as for the receptacles themselves. Some of my electricians have found the cheapest cutter for this is the conduit size step drill that is available from harbor freight for around $10. You can also use a 7/8 hole saw. -Bill KB8WYP -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Clawson Sent: Thursday, January 29, 2015 1:24 PM To: Topband Reflector Subject: Re: Topband: Elimination of Treadmill RFI on 160 meters Nice to hear all the comments, recommendations, and indeed some success stories here. I too have a treadmill problem. Although I'm blessed with a radio-friendly spouse who always asks before she starts it up, I'd like to add a line filter. Ferrites on the cord don't by themselves squelch it. Murphy dictates that the new one will show up when she's in the middle of her workout. How about some outlet box recommendations? The electrics are not the hard part for me, it's the mechanics. I've been looking for a suitable box to mount it all in and coming up kind of dry. Maybe I'm not looking for the right keywords. Seems simple, a box with a cutout for two 120VAC outlets and enough room inside for a line filter and some toroids. A strain relief clamp would be a big plus but something else can always be worked out for that. In the past I've bolted a surface mount outlet box to another project box but it's kinda big and ugly, and more expensive than it ought to be. 73 and thanks in advance, Carl WS7L _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
On 1/29/2015 10:23 AM, Carl Clawson wrote: Nice to hear all the comments, recommendations, and indeed some success stories here. I too have a treadmill problem. Although I'm blessed with a radio-friendly spouse who always asks before she starts it up, I'd like to add a line filter. Ferrites on the cord don't by themselves squelch it. Ferrites on the cord don't work on 160 meters if they are of the single turn class: easy to use, but ineffective, clamp on beads. What does have a chance of working is 15 or so turns on a 2.4 inch O.D. toroid. Impedance varies as the square of the number of turns, so 15 turns is like 225 beads. Fair-Rite Products also makes some large clamp on ferrites that you can wind with a lot of turns. The advantage of these is that the plug on the end of the cord is no longer a constraint. Rick N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
Ganged outlet boxes are no longer a good option. In years past, they were fairly beefy. Modern ones are lighter gauge steel and too flimsy to hold together outside of a wall (and too flimsy in the wall too, IMHO). They also usually use internal cable clamps with a screw that sticks out the back so they don't make a nice assembly to use in the field. Extension rings suffer from the same flimsy problem these days. If you use a 4 inch box (usually called a 4 square in the trade), I recommend getting the drawn kind (one formed piece with round corners) instead of the more common welded kind (two end plates tack welded to the rest of the assembly with sharp square corners). The drawn kind I think are made by Steel City and Home Depot has them. If you can get the deep version (2-1/8 deep), you'd have more room for filters inside than with the more common version that is around 1-1/2 deep. I think 4-11 boxes are even better if you need to mount things inside, but I've only ever seen them in the welded style. Note that the extension rings for 4-11 boxes are DIFFERENT! They have a round cutout between the box and the ring instead of the square cutout you'd expect! They are probably NOT very suitable for this application! The BX clamps work but the rubber cable glands are better for not much more money. Home Depot actually does carry a Halex version of the cable gland, but the Appleton and Hubbel ones are MUCH MUCH better. And why would the manufacturer spend 15 cents when their customers can spend $50 of their own money instead? ;-) -Bill A deep 4 inch box? Add extension rings if necessary? Ganged outlet boxes? http://www.mcmaster.com/#standard-outlet-boxes/=vohae8 I know I've seen on the web somewhere, a Grow-Light filter with 3 big 2.4 toroids all in a 4 inch box. I don't think there was any room left for outlets. I use 4 inch boxes for all sorts of ham accessories (having nothing to do with 120VAC power). They are nice and heavy and stay put. The 3/8 BX clamps work great for cable strain relief. If the treadmill manufacturer had just included 15 cents of waveshaping at the MOSFET, all the external filtering would be completely unnecessary. Tim N3QE [snip] _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
Ferrites on the cord don't work on 160 meters if they are of the single turn class: easy to use, but ineffective, clamp on beads. What does have a chance of working is 15 or so turns on a 2.4 inch O.D. toroid. Impedance varies as the square of the number of turns, so 15 turns is like 225 beads. Fair-Rite Products also makes some large clamp on ferrites that you can wind with a lot of turns. The advantage of these is that the plug on the end of the cord is no longer a constraint. People just love adding series impedances, that what we do as hams. :) Bypassing is usually much more effective than simply adding series impedances. Sometimes bypassing alone is more than enough. 90% of the time when I clean up an offshore SMPS for Ham use, it is just moving ground leads and bypassing.:) 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
On Thu,1/29/2015 11:18 AM, Tim Shoppa wrote: A deep 4 inch box? Add extension rings if necessary? Ganged outlet boxes? Slide #6 in http://nccc.cc/pdf/CQP-RFI2013-2.pdf shows how I mounted a 20A line filter in deep multi-gang boxes. Each box is sized to hold a single duplex outlet or switch. I've forgotten the correct name for them, but they're in the big box stores, about $2 per section. All it takes to gang them is remove one side cover of the end boxes and both side covers of the interior boxes and screw them back together. I bought these at Home Depot. I later found a cover for the rest of the box -- some of the less common stuff like multi-gang covers I had to buy online from amazon, etc. Another good way to do it is to buy a suitable length of ordinary extension cord (same big box store), break it close to the male plug connect the two ends to the line filter, going in and out of the box with compression fittings, and winding a common mode choke on the longer output side of the cable. I've done that with a cable where the output went to a multi-output strip or 3-way split. When you're wiring to the filter (and outlets) ALL THREE WIRES MUST be connected on both sides. Here's a link to ARRL's page about grow lights. http://www.arrl.org/grow-light-rfi It includes a link to line filters that W0IVJ and W0QE have developed. From the spectrum sweeps, it's not clear to me that their filter goes down below 40M. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
On Thu,1/29/2015 1:23 PM, Tom W8JI wrote: People just love adding series impedances, that what we do as hams. :) Bypassing is usually much more effective than simply adding series impedances. Sometimes bypassing alone is more than enough. 90% of the time when I clean up an offshore SMPS for Ham use, it is just moving ground leads and bypassing. :) This snide remark ignores the fact that it is generally not practical (nor is it good politics) to go inside your neighbor's equipment to add bypass capacitors. Nor is it practical to open up a wall wart, nor even most consumer equipment. It also ignores the fact that much of RFI at HF is common mode, not differential mode, caused by bonding failures (the Pin One Problem and its power systems equivalent). And it ignores the fact that it is often the cable shield or the power system equipment ground that is carrying the RF noise current, for reasons noted in my earlier post. The use of common mode chokes that have a high value of resistive impedance at the desired operating frequency is an effective fix for common mode RFI the results from poor equipment design. Your only problem is that you didn't think of it first. Think about it -- a single ferrite core applied to wiring from a noise source has a low Q parallel resonance in the range of 150 MHz, causing to appear as a resistance in the range of several hundred ohms. (Look at the impedance curves on the data sheet for any Fair-Rite suppression part. If you don't recognize that as a parallel resonant circuit, you failed electrical circuits 101.) The impedance of that single core is enough to get the equipment past Part 15 in the VHF range, so they stop there. The resonance is in the wrong place for HF, so we wind turns to move it down where we need it, and in the process, multiply both R and L by the square of the turns, and C by the number of turns. Again, all of this is fundamental circuit concepts. Do all systems NEED 5-10K ohms resistive Z? Of course not, BUT most systems are used over a wide range of frequencies and have a wide range common mode impedances -- anything from high to low, capacitive to inductive to resistive. A simple inductor resonates with a capacitive common mode circuit, which increases the common mode current, making the problem worse. But resistance ALWAYS reduces the current -- by how much depends on the impedance of the circuit. I have always recommended high values of common mode Z because it never makes the problem worse, because it doesn't require the person with the problem to be a trained engineer, because it's relatively simple and inexpensive, and because we don't have to go inside the box. The only potential problem is if the conductor being choked has enough common mode current to fry the choke -- for example, a high power antenna system. If you happen to BE the product engineer, certainly you should be solving the problem inside the box before the product goes out the door. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
On Wed,1/28/2015 8:34 AM, Brad Rehm wrote: I've never looked closely at the problem, but I wonder how the 31-mix cores behave in the presence of high-current, 20 kHz fundamental frequency pulses that drive the PWM motor in our treadmill. That mix would suppress the higher-frequency harmonics, but would the core eventually change its properties because of the transients it has to live with. (The load current rating of our treadmill was 15 Amps.) Is it possible the core could begin to generate more noise at Topband frequencies if it became easier to saturate? Several points. First, RF current on the green wire will couple to the other conductors, so ALL conductors should be run through the common mode choke. Second, since all conductors are going through the choke, the baseband magnetic field (that is, 60 Hz and harmonics of 60 Hz) is zero unless the load device is miswired with neutral connected to the green wire and the load device is grounded. Except for lightning, your concerns with transients changing the core is not at all warranted. Based on my experience with noisy stuff, I always apply the common mode choke as close as practical to the noise source, and nearly all of my various electronic loads are plugged into multi-boxes into which I have installed a line filter. We're lucky out here around Silicon Valley in that we still have a big electronics surplus warehouse. One thing they had a lot of several years ago was a selection of AC line filters from Delta, Corcom, and a few smaller vendors. I bought a bunch for a buck or two apiece. http://www.halted.com/ 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
Jim, No question that a separate filter for the green wire can make a difference when there's RF current on that lead. But I'd wait to add the extra filter until I was sure it was needed. The case yesterday is an example of one in which it wasn't. We weren't surprised, because we'd already pre-tested the fix with another filter, checked for currents on the ground lead and satisfied ourselves that a properly-selected 2-circuit filter would cure the problem. I suspect that cases in which green-wire filtering is needed could be cured with a 3-phase line filter. Something like Corcom's 20AYP6C. This would be easier to install, but the cost would be 4 to 6 times that of the filter we used yesterday. I've found them at hamfests, though. I've never looked closely at the problem, but I wonder how the 31-mix cores behave in the presence of high-current, 20 kHz fundamental frequency pulses that drive the PWM motor in our treadmill. That mix would suppress the higher-frequency harmonics, but would the core eventually change its properties because of the transients it has to live with. (The load current rating of our treadmill was 15 Amps.) Is it possible the core could begin to generate more noise at Topband frequencies if it became easier to saturate? Brad KV5V On Tue, Jan 27, 2015 at 10:13 PM, Jim Brown j...@audiosystemsgroup.com wrote: On Tue,1/27/2015 3:19 PM, Brad Rehm wrote: You make a good point about the difference between our definition of CM noise and the definition implied in Part 15. If the external torroid made a difference for you, then it's important and worth having. Exactly. The commercial filter addresses only differential mode. The ferrite choke is necessary to suppress what we (and Part 15) call common mode. Several years ago, I put some good quality line filters in electrical boxes for use on Field Day and California QSO Party county expeditions with our Yamaha generators. They didn't do much -- to kill the moderate trash, I had to to wind multiple turns of the line cord through a big ferrite core. I used a big 1-in i.d. Fair-Rite #31 clamp-on that's a couple of inches long (the biggest they make). Depending on the diameter of the line cord I had used, I was able to get either three or four turns through it. That was enough to kill 20-10M, which is what we heard in the tri-banders that were close to the generator, and for the 80/40 dipoles that were much further away. If the 80/40 antennas had been closer we would likely have needed more turns. Did the commercial line filters do any good? I don't know -- but they certainly didn't hurt, and the boxes I put them in have a bunch of outlets on them for power distro. :) OTOH, one of the guys used to bring his big RV with a noisy generator on-board. All I used there was as many turns as I could get through a small stack of 1.4-in i.d. #31 toroids as close as I could get them to the generator, and it did the job. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
Hi Brad, Great to hear you had similar results. The 20VR1 and the 20DRGG5 filter appear to be of very similar design (two stage filters, and component values not vastly different). The 20VR1 looks to be double the price of the 20DRGG5, but it might offset some of the additional cost if it allows elimination of the additional Toroid core choke. Since all cases are different I would have to test the 20VR1 in my application to see if it would indeed allow elimination of the Toroid core choke, but I doubt I would be able to eliminate the Toroid core choke for the following reason that Jim K9YC mentioned on another reflector : What the power industry calls common mode is NOT what we call common mode. They are talking about the voltage between neutral and the green wire. We are talking about current that is flowing in the same direction on three conductors. In my case the additional Toroid core choke had a very noticeable impact, and I now can't tell when the treadmill is on when using the combination of both filters. P.S. I sent an e-mail to the manufacturer of our Treadmill, and they never responded. I am now going to call them on the phone in an attempt to get in touch with their design engineers, and likely will also file a complaint with the FCC regarding treadmills in general. There are a couple more treadmills near my home that generate very strong RFI, but fortunately they normally use their Treadmills during the day, and I operate mostly at night. 73, Don (wd8dsb) On Tue, Jan 27, 2015 at 1:26 PM, Brad Rehm bradr...@gmail.com wrote: Don, FWIW, today, W5UJE and I dealt with a treadmill problem similar to yours by installing a commercial line filter between the line and the treadmill electronics. A Corcom/TE Connectivity 20VR1 filter reduced the 40m and 75m noise at his receiver from S9+10db to less than S2 (his noise floor this morning). The 20 Amp rating was needed because the manufacturer's published current requirement for the treadmill was 15 Amps. In measurements we'd made earlier, we found that this was a common-mode problem and that the noise spurs were about 20 kHz apart when the treadmill was operating under a moderate load. The spectrum scope on his radio showed 20 kHz-spaced broadband noise up through 29 MHz, peaking between 1.8 and 15 MHz. The line filter we chose offers 10-20 dB of supperssion below 50 kHz and 60-80 dB of suppression between 300 kHz and 29 MHz. No additional filtering with torroids or capacitors was needed. In other words, our results were similar to yours, and one wonders how manufacturers can say these things meet Part 15 requirements for conducted emissions. Brad KV5V On Mon, Jan 26, 2015 at 7:22 PM, Don Kirk wd8...@gmail.com wrote: Treadmill combination filter update. Today I replaced the 10 amp commercial filter with the 20 amp version of the filter, and the results are similar. Below are a few measurements on 160 meters and 80 meters showing how effective the combination of the two filters are (14 turn toroid choke, and commercial filter model 20DRGG5 made by Delta) in reducing my treadmill RFI. *1.8068 Mhz* No Filters : 19db over S9 With Filters : S7 which is my noise floor *1.8291 Mhz* No Filters : 15db over S9 With Filters : S7 which is my noise floor *3.5250 Mhz* No Filters : 28db over S9 With Filters : S6 which is my noise floor *3.5475 Mhz* No Filters : 25db over S9 With Filters : S6 which is my noise floor The 3.5250 Mhz readings indicate the filter is knocking the signal down at least 46db (and probably more). 73, Don (wd8dsb) _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
Don, You make a good point about the difference between our definition of CM noise and the definition implied in Part 15. If the external torroid made a difference for you, then it's important and worth having. We can't be too optimistic about the manufacturer's interest in fixing this kind of problem. He won't be willing to install a $50 or even $25 filter to satisfy a few hams who have EMC complaints. At the same time, because the products you and I have dealt with responded so well when we added filters, we have to wonder if and how the Part 15 compliance testing was done. In the EMC lab where I worked, we tested them under load (with someone walking on the treadmill or with a fixed load applied), but some labs might be tempted to test only the uP controller. It's hard to imagine how this could be justified, because the belt is usually driven with square pulses. RF noise from these can be hard to suppress. I didn't think to check the label for the machine I worked on, but I wonder if you've looked for an FCC compliance mark on your treadmill. If it has one, it might be interesting to go to the FCC URL and look at the report that was filed for it. And BTW, if the treadmill was manufactured in the far east, the mark could be bogus or filtering could have been deleted after the initial testing was done. This kind of thing isn't all that unusual. 73, Brad KV5V On Tue, Jan 27, 2015 at 4:05 PM, Don Kirk wd8...@gmail.com wrote: Hi Brad, Great to hear you had similar results. The 20VR1 and the 20DRGG5 filter appear to be of very similar design (two stage filters, and component values not vastly different). The 20VR1 looks to be double the price of the 20DRGG5, but it might offset some of the additional cost if it allows elimination of the additional Toroid core choke. Since all cases are different I would have to test the 20VR1 in my application to see if it would indeed allow elimination of the Toroid core choke, but I doubt I would be able to eliminate the Toroid core choke for the following reason that Jim K9YC mentioned on another reflector : What the power industry calls common mode is NOT what we call common mode. They are talking about the voltage between neutral and the green wire. We are talking about current that is flowing in the same direction on three conductors. In my case the additional Toroid core choke had a very noticeable impact, and I now can't tell when the treadmill is on when using the combination of both filters. P.S. I sent an e-mail to the manufacturer of our Treadmill, and they never responded. I am now going to call them on the phone in an attempt to get in touch with their design engineers, and likely will also file a complaint with the FCC regarding treadmills in general. There are a couple more treadmills near my home that generate very strong RFI, but fortunately they normally use their Treadmills during the day, and I operate mostly at night. 73, Don (wd8dsb) On Tue, Jan 27, 2015 at 1:26 PM, Brad Rehm bradr...@gmail.com wrote: Don, FWIW, today, W5UJE and I dealt with a treadmill problem similar to yours by installing a commercial line filter between the line and the treadmill electronics. A Corcom/TE Connectivity 20VR1 filter reduced the 40m and 75m noise at his receiver from S9+10db to less than S2 (his noise floor this morning). The 20 Amp rating was needed because the manufacturer's published current requirement for the treadmill was 15 Amps. In measurements we'd made earlier, we found that this was a common-mode problem and that the noise spurs were about 20 kHz apart when the treadmill was operating under a moderate load. The spectrum scope on his radio showed 20 kHz-spaced broadband noise up through 29 MHz, peaking between 1.8 and 15 MHz. The line filter we chose offers 10-20 dB of supperssion below 50 kHz and 60-80 dB of suppression between 300 kHz and 29 MHz. No additional filtering with torroids or capacitors was needed. In other words, our results were similar to yours, and one wonders how manufacturers can say these things meet Part 15 requirements for conducted emissions. Brad KV5V On Mon, Jan 26, 2015 at 7:22 PM, Don Kirk wd8...@gmail.com wrote: Treadmill combination filter update. Today I replaced the 10 amp commercial filter with the 20 amp version of the filter, and the results are similar. Below are a few measurements on 160 meters and 80 meters showing how effective the combination of the two filters are (14 turn toroid choke, and commercial filter model 20DRGG5 made by Delta) in reducing my treadmill RFI. *1.8068 Mhz* No Filters : 19db over S9 With Filters : S7 which is my noise floor *1.8291 Mhz* No Filters : 15db over S9 With Filters : S7 which is my noise floor *3.5250 Mhz* No Filters : 28db over S9 With Filters : S6 which is my noise floor *3.5475 Mhz* No Filters : 25db over S9 With Filters : S6 which is my noise floor The 3.5250 Mhz readings
Re: Topband: Elimination of Treadmill RFI on 160 meters
are talking about current that is flowing in the same direction on three conductors. In my case the additional Toroid core choke had a very noticeable impact, and I now can't tell when the treadmill is on when using the combination of both filters. P.S. I sent an e-mail to the manufacturer of our Treadmill, and they never responded. I am now going to call them on the phone in an attempt to get in touch with their design engineers, and likely will also file a complaint with the FCC regarding treadmills in general. There are a couple more treadmills near my home that generate very strong RFI, but fortunately they normally use their Treadmills during the day, and I operate mostly at night. The FCC requires testing of power line conducted emissions with a line sample unit that connects from each conductor to ground. One LISN is specified to go from each current-carrying conductor to ground. The safety ground, since it does not carry current, is grounded. The flaw in this system is that differential voltages between current carrying wires are not measured, and anything on the safety ground isn't measured. Noise voltage is only measured from individual current carrying conductors to ground, and the safety ground is grounded and not measured. Filters inside devices and many outside filters often route the noise right out on the safety ground, in differential to the equipment case (if large it acts like a groundplane) or other connecting wired systems like a Telco line or data interface cable. Since the FCC mandates the safety ground and other grounds be grounded to the test equipment RF measurement groundplane, that path or ground loop paths are not measured. This allows some pretty ratty stuff to pass FCC tests. The FCC should have created a better test, instead of assuming all grounds in the real world were common-connected with near zero impedance. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
On Tue,1/27/2015 3:19 PM, Brad Rehm wrote: You make a good point about the difference between our definition of CM noise and the definition implied in Part 15. If the external torroid made a difference for you, then it's important and worth having. Exactly. The commercial filter addresses only differential mode. The ferrite choke is necessary to suppress what we (and Part 15) call common mode. Several years ago, I put some good quality line filters in electrical boxes for use on Field Day and California QSO Party county expeditions with our Yamaha generators. They didn't do much -- to kill the moderate trash, I had to to wind multiple turns of the line cord through a big ferrite core. I used a big 1-in i.d. Fair-Rite #31 clamp-on that's a couple of inches long (the biggest they make). Depending on the diameter of the line cord I had used, I was able to get either three or four turns through it. That was enough to kill 20-10M, which is what we heard in the tri-banders that were close to the generator, and for the 80/40 dipoles that were much further away. If the 80/40 antennas had been closer we would likely have needed more turns. Did the commercial line filters do any good? I don't know -- but they certainly didn't hurt, and the boxes I put them in have a bunch of outlets on them for power distro. :) OTOH, one of the guys used to bring his big RV with a noisy generator on-board. All I used there was as many turns as I could get through a small stack of 1.4-in i.d. #31 toroids as close as I could get them to the generator, and it did the job. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
On Tue,1/27/2015 4:08 PM, Tom W8JI wrote: The flaw in this system is that differential voltages between current carrying wires are not measured, and anything on the safety ground isn't measured. Noise voltage is only measured from individual current carrying conductors to ground, and the safety ground is grounded and not measured. Exactly right, Tom. A common design/manufacturing defect is that the green wire fails to make contact with the shielding enclosure, but instead goes to common on a circuit board, which may or may not ever find the chassis. This defect, which is the power system equivalent of a Pin One Problem, puts noise on the green wire. You may remember that we corresponded several years ago about Astron power supplies, in which a very common defect is that the green wire is soldered to the mounting lug of a terminal strip, which is insulated from the chassis by paint. The same mounting lug is the point where V- is bonded, so it never finds the chassis either. AND, wiring for both V- and the green wire act as antennas for both TX and RX. I have long suspected that similar defects are at least partially responsible for noise conducted onto coax and AC lines from consumer products of all sorts. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Elimination of Treadmill RFI on 160 meters
Treadmill combination filter update. Today I replaced the 10 amp commercial filter with the 20 amp version of the filter, and the results are similar. Below are a few measurements on 160 meters and 80 meters showing how effective the combination of the two filters are (14 turn toroid choke, and commercial filter model 20DRGG5 made by Delta) in reducing my treadmill RFI. *1.8068 Mhz* No Filters : 19db over S9 With Filters : S7 which is my noise floor *1.8291 Mhz* No Filters : 15db over S9 With Filters : S7 which is my noise floor *3.5250 Mhz* No Filters : 28db over S9 With Filters : S6 which is my noise floor *3.5475 Mhz* No Filters : 25db over S9 With Filters : S6 which is my noise floor The 3.5250 Mhz readings indicate the filter is knocking the signal down at least 46db (and probably more). 73, Don (wd8dsb) On Thu, Jan 8, 2015 at 8:14 AM, Don Kirk wd8...@gmail.com wrote: For many years my wife's treadmill caused strong interference on 160 meters when it was in use, and yesterday I was able to completely eliminate the RFI using a combination of two different filters (a commercial line filter that provides both common mode and differential mode filtering, and 14 turns of the power cord on a 2.4 OD Fair-Rite #31 mix toroid core based on the K9YC hams guide to RFI document). I created a simple website that documents my tests and the filters used, and for those interested the website URL is http://sites.google.com/site/treadmillrfi/ The website contains a link to a video on youtube where you can actually see the effectiveness of the filters. 73, Don (wd8dsb) _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Elimination of Treadmill RFI on 160 meters
For many years my wife's treadmill caused strong interference on 160 meters when it was in use, and yesterday I was able to completely eliminate the RFI using a combination of two different filters (a commercial line filter that provides both common mode and differential mode filtering, and 14 turns of the power cord on a 2.4 OD Fair-Rite #31 mix toroid core based on the K9YC hams guide to RFI document). I created a simple website that documents my tests and the filters used, and for those interested the website URL is http://sites.google.com/site/treadmillrfi/ The website contains a link to a video on youtube where you can actually see the effectiveness of the filters. 73, Don (wd8dsb) _ Topband Reflector Archives - http://www.contesting.com/_topband
