Is There A Plug In Filter To Reduce Line Interference On My Garage Workshop Radio?
MARK, N1LO, PUT LOTS OF HOURS AND Difficult Work INTO THIS Commodity
FOR ALL OF The states TO USE.
Past N1L0
USED WITH PERMISSION..THANKS Marker! New additional information on RFI near end of commodity
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Nathan Karras
North Systems Technologies
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RADIO FREQUENCY INTERFERENCE (RFI) Notes Past Mark D. Lowell, N1LO. Outset posted in December 1999 This document is a series of notes that I accept made concerning RFI and TVI problems and resolution after reading and digesting the bulletin archives of the RFI forum sponsored by the folks at www.contesting.com. The archive is located at: http://world wide web.contesting.com/_rfi/ ONLINE RFI REFERENCES 3 ONLINE RFI REFERENCES PUBLICATIONS FOR REFERENCE A good volume on EMI that every active ham ought to own is the ARRL's "Radio Frequency Interference: How to Discover It and Ready It". They've updated it and it's at present called "The ARRL RFI Volume". I all the same need to buy the new i, but the one-time 1 is really excellent! Don't take immediate responsibility for the problem. Brand information technology clear that although y'all are the source of an exterior radio indicate, the neighbor'due south device is supposed to exist designed to decline it. Practice not perform modifications on AC powered equipment that is not your own. Remember -- house Air conditioning power is dangerous and you may be blamed if anything EVER goes wrong with the device or house wiring. These modifications must only exist performed past qualified service personnel! Install a low-pass filter on your HF station. For telephone interference issues, offering to loan the neighbour an RF resistant telephone (run across telephone department) for testing and have him unplug all other phones. In regards to problems with close neighbors complaining about your radio interfering with their computers: Tell them to take their trouble upwardly with the computer manufacturer. DO NOT, under any circumstances, work on a neighbor's reckoner even if he is a close friend. The reason for this is that at a later appointment if and when any problem occurs (particularly a data crash) you lot will be blamed. FCC rules on estimator RFI are uncomplicated and clear cut. Computers are function xv devices and equally such they may not interfere with any licensed radio service and must take any interference Rectification and overload are both problems with the pattern of the affected equipment, and after decades of investigation, the FCC knows this. That's why their policy is such as information technology is at present. The FCC cannot get laws enacted to correct this by forcing manufacturers to properly design stuff so they've backed off and are non doing anything almost information technology themselves. If the neighbor is unwilling to cooperate, the FCC won't even desire to talk with them. They are instructed by the FCC to contact the manufacturer who made the lacking equipment for a solution. Sort of a "free market" solution. The "standard" splitters RS sells are in some cases quite leaky; notwithstanding, the "gilded" series ones they sell are pretty tight. They are much preferable. Skid a grounded, tubular braid (from some old coax, possibly) over connecting cords on the device. Shield the device with a metal box, or wire screening. Orient the device into a different position or move the antenna on the radio device. Spray plastic enclosures with an EMI shielding spray to plow them into shielded cases, and ground them. The appropriate ferrite mix to utilize for HF and below is type 73, 75, and 77 for higher permeability. For VHF/UHF, use type 43. Hither is a source for cores suitable for HF: From an ARRL Handbook: Mix Colour Textile ? Temp f (MHz) Notes stability (ppm/?C) Radio Shack Ferrites (if you lot can detect them) The second Radio Shack ferrite is a rectangular device which opens up and allows the ferrite halves to be separated so multiple turns tin can exist wrapped effectually it. It is 1.675 inches long by i.125 inches broad past .375 inches thick. The opening is much larger in this ferrite, and so more than turns can be wrapped around it than the cylindrical one. The values shown are for a single wire through the ferrite. Unlike the cylindrical ferrite, in that location is no inductance height. As with all coils, increasing the number of turns increases the inductance and ESR by the square of the increase. For instance, if one turn gives 1 uH and 10 ohms, two turns volition give 4 uH and forty ohms, iii turns would requite 9 uH and 90 ohms and then on. 1 inexpensive source of toroids is to use deflection yoke cores from junk television sets or monitors. They are bulky, even from a pocket-size tv, but work well. Multiple passes of the cable are possible to achieve high isolation reactance. These may not have the permeability for the frequency of interest, so experiment. Making common-mode chokes To realize effective chokes in few turns it is a need to use materials whose permeability is very loftier, 2000 or more. Large cablevision, such as monitor cables, are impractical to wind. The solution hither is to use large, divide toroids and mate the halves tightly afterwards winding the cable around each half. "Some improvement" with ferrites indicates that more ferrites added may cure the problem. Radio Shack "Clamp-On Chokes" must have 5 turns or more to be effective on 80 meters. Split beads are most ten times as good (Palomar FSB-i/2 or equivalent). TELEPHONES There is some info on RFI proof phones in the FCC's Interference Handbook (which is gratuitous if you inquire for them at 888-CALL-FCC): TCE Labs RR9 Box 243D New Braunfels, TX 78133 (800)KILL-TVI If you lot do have interference, effort to eliminate it with filters. All of the filters should be mounted as close to the telephone as possible. First, effort a telephone line filter. You lot can buy a commercial product, or make ane with nearly 10 turns onto an FT-140-43 ferrite core. If the interference is primarily from forty m and below, an FT-140-75 cadre may work a bit better. Y'all may besides have to filter the handset cord. Yard-Com sells handset filters. If the telephone or telephone device has a connexion to the AC line, usually through i of the "wall cube" type supplies, y'all may need to try a common-style choke on the power lead to the telephone (10 turns on an FT-140-43 or -74). Modern electronic telephones are potentially susceptible to radio-frequency interference [RFI] considering they contain many silicon diodes which act every bit crystal rectifiers. The crystal rectifiers catechumen inaudible, RF energy into audio-frequency energy which can exist heard in the earphone. This turns the phone into a crystal-set/radio-receiver in the presence of moderate to potent RF signals. Electronic telephones also comprise transistors which can dilate RF signals. This increases the RF-sensitivity of the telephone. The antenna for this unwitting radio receiver is the telephone wiring in the walls and attic of the building where the phone is located. The cyberspace consequence is that people who live well-nigh an AM radio station may hear music over their telephones. People who live near airports may hear pilots talking with the control tower. Those who live near an amateur radio station may hear garbled speech communication in their telephones. A properly engineered telephone will not let RF-free energy to enter the telephone circuits which incorporate the components that act as crystal rectifiers. Including an RF-energy filter in the pattern of a telephone would increase the retail price of the telephone by less than $1. RF-filter Installation MFJ electronics sells an RFI proof computer keyboard (model MFJ-551) . TOUCH LAMPS The easiest route here is simply to go rid of these pesky things, and return them to the store, if possible. A uncomplicated cure for those touch-controlled lamps that plow themselves on and off during nearby radio transmissions on 40 and lxxx meter functioning. A 1k ohm resistor in serial with the signal input pb (from the lamp base) to the encapsulated circuit that operates the lamp may cured the problem for me. If this isn't sufficient, add an RF asphyxiate (100 uH, 139 mA) in serial with the Many of the new computers are omitting the RFI filter in the power supply that keeps the garbage from the switching manner supply from entering the AC mains. Excellent results are possible in near eliminating the interference past replacing the AC connector on the back of the power supply with an integrated AC connector and RFI filter such every bit the Corcom 6EF1. Some power supplies accept a identify on the excursion board for a filter just have eliminated the components to save some money, and have just placed jumpers in the positions where the components had been. It would be possible to make a new filter and add information technology to the existing location--or to add information technology between the excursion board and the existing connector----but the commercial Corcom filter is probably the all-time and easiest way to go. The commerical filter has one.0 mH coils (bifilar rated at 6 amps in series with each side of the line. On the computer The filters are available from most Us electronics suppliers for around $ten or then, merely can ofttimes be found in the surplus market place for $one-$2, such as the iii amp version (3EF1, a little marginal). In that location is besides a 3EF2 and a 6EF2 that will work and may be even easier to fit inside the power supply--their terminals come out the top/bottom rather than the end. If adding and Air conditioning mains RFI filter doesn't completely cure the trouble then additional RFI suppression volition be needed--just in my cases it eliminates the trouble. One instance source: If you lot need one of these AC line filters, they are bachelor for $5.41 ea. (part # 562-857-03/47) from Mouser Electronics . You lot may as well achieve reduction of video noise when powering the monitor from the accessory a.c. socket on the dorsum of the computer p.south., instead of just a random socket in the station. If you lot are experiencing issues or problems with your computer that may accept time to fix, keep in mind computer rental Package GEAR (TNC) FUEL PUMPS DANGER! The primary noise source is normally slack bong insulators. Those bell shaped insulators you lot see at the ends of power line runs have metal parts which, if not electrically bonded, will arc at a 120Hz rate. Without sufficient tensioning, a thin oxide layer builds up in metal joints. They arc simply considering they are in such close proximity to loftier voltage (usually 4, 7.v, or 12 KV!). One time you find a bad pole, write its address and whatever identifying numbers you tin can spot on it and plough a "TVI" report into the power visitor. The thing to watch though, is that your study may not be written downward correctly, The folks you talk to at the power company don't unremarkably understand RF or think that anyone likewise their ain technician is incapable of understanding such an arcane subject. Try to get them to contact you lot and, preferably, allow you to exist nowadays when the piece of work is done. If your problem report is merely handed to a utility line repair foreman, he is probable to simply go to your dwelling house address and decide that he can hear the brawl game on his truck radio just fine and so non bother checking any further. Y'all want to exist able to give him the right repair information and then he will really piece of work on the real trouble.
Grand.D.Lowell, N1LO October, 1998 Progress: Through July 1999 archive Cheque http://www.qsl.net/n1lo/rfi.htm for the latest update
The existence, accurateness, content and organization of whatsoever section may change at any fourth dimension equally new discoveries, understandings, and concepts arise. I add new sections whenever appropriate.
PUBLICATIONS FOR REFERENCE three
RESOLVING RFI ISSUES WITH A Neighbour iii
DO's AND DON'TS three
GETTING THE FCC INVOLVED three
USING Low PASS AND BAND PASS FILTERS ON TRANSMITTERS 4
CHECKING A CABLE TV Organisation FOR LEAKS 4
General RFI-PROOFING MEASURES FOR DEVICES 4
FINDING AND SELECTING FERRITE CORES v
FERRITE MIX five
RADIO SHACK FERRITES 5
MAKING COMMON-MODE CHOKES half-dozen
FIXES FOR DEVICES SUSCEPTIBLE TO RFI half-dozen
TELEPHONES 6
TELEVISIONS 8
F-CONNECTORS 9
ANTENNA PREAMPS ix
Audio AMPLIFIERS nine
Simple COMMON-Manner CHOKE 9
Figurer KEYBOARDS 9
YAESU ROTATORS 10
GARAGE DOOR OPENERS 10
STOPPING COMMON SOURCES OF INTERFERENCE TO RADIO EQUIPMENT 10
Touch on LAMPS x
LIGHT DIMMERS 10
Night LIGHTS 11
Automated LIGHTS eleven
Low VOLTAGE LAMPS 11
DIGITAL TEMPERATURE DISPLAYS 11
COMPUTERS 11
COMPUTER MONITORS 12
TELEVISIONS 12
PACKET GEAR (TNC) 12
AUTOMOTIVE SOURCES 13
FUEL PUMPS 13
Electrical FENCES 13
TRACING Ability LINE Dissonance thirteen
ELEVATED POWER LINES 13
Clandestine FEEDERS fourteen
AMIDON Products Technical Reference
http://world wide web.bytemark.com/amidon/content0.htm There is detailed explanation
and design info here likewise as an excellent section on EMI/RFI
http://www.bytemark.com/amidon/emi-rfi.htm
http://world wide web.arrl.org/tis
http://www.fcc.gov/cib/Publications/tvibook.html
Practise's AND DON'TS
ARRL publishes an RFI pamphlet, written specifically to assist explain interference to your neighbors. To get a couple of copies, transport an SASE to the ARRL Technical Section Secretary, 225 Main St, Newington, CT 06111, along with a asking for "2 RFI pamphlets." The text of this pamphlet is available on ARRL'due south Spider web page, just the bodily printed pamphlet is more than constructive with your neighbor than a downloaded Spider web folio, in near cases.
The FCC no longer investigates RFI complaints to telephone, TV or amusement systems. You tin call their 800 number (888-CALL-FCC) and listen to the FCC'southward RFI bulletin. It is educational. You might want to give this number to your complaining neighbour since information technology tells him it's near likely his equipment at fault-not yours. Y'all can besides find out how to gild The FCC's interference handbook which tells the same story. Become an extra 1 for the neighbor if you want to be overnice of course.
1 chip of advice: It actually helps to clean up your Television/Stereo & telephones, so that you can bespeak at your equipment saying "My Tv/Stereo/Telephone doesn't get any interference, then it must be your equipment." While solving your ain RFI problems you lot'll learn how to assist your neighbors with theirs (should they finally ask for help). When helping a neighbor it's a good idea to have another local ham familiar with RFI act equally a liaison or 3rd party who is non interested in the dispute. Contact your local order or the ARRL for the proper noun of the local TS (Tech Specialist) who is willing to help out in this capacity.
About whatsoever low-pass filter will offer at least xxx-lx dB of stop-band attenuation. Good units are fabricated by Bencher, Drake and Ice. Proceed the jumper between the transmitter and filter equally brusque as possible to prevent the jumper from condign any kind of antenna for harmonics. In nearly cases, if the interference is acquired past transmitter unwanted emissions, this will exist quite enough to make the problem go away.
The main purpose of a low-pass xmit filter is and then that when you Exercise have an interference problem, you tin can point to information technology with pride.
Virtually cases of consumer interference are caused by fundamental overload, not transmitter harmonics. If the only requirement is to attenuate harmonics, the right solution is to utilize a lowpass filter or a harmonic notch filter - at any frequency. One important difference at VHF is that the percent frequency change is normally much smaller than at HF. This means that the harmonic frequencies are essentially stock-still, so harmonic notch filters using coax stubs can perform very well indeed. See the web page, http://www.ifwtech.co.united kingdom of great britain and northern ireland/g3sek/swxfiltr/swxfiltr.htm , for details of the harmonic notch filters past G4SWX which have excellent performance, can be congenital in minutes, toll literally a few pennies, and can handle a kilowatt. Checking a cable Goggle box arrangement for leaks If your neighbor is on cable, check that start. The easiest manner to narrow this down is to come across if at that place are leaks in the system. On cable, they utilize 2 frequencies to each aqueduct. The easiest one to use to bank check for us is ch. eighteen. Its picture is sent very near 145.26 and its sound about 149.76 . If you have a extended coverage receive two meter and a beam antenna, put it on 149.760 open up up the squelch, and rotate it and listen for the vocalisation leaks from ch. eighteen. In one case you become the heading. take a HT and go for a walk. You very well may find information technology seems to be stiff and then you lot may need to check for leaks in your own house. Become it as close as y'all tin with the HT, utilise your trunk equally a directional attenuator to become some directional headings on the HT.
In one case y'all close in to the house, room, pole or what e'er, you tin remove the antenna from the HT to pin point the verbal location of the leak. You lot may discover the problem a Cable Set TV tuner, a homeowner's own cablevision addition with non Cable Tv rated RG59, a splitter with a unused port and no terminating resistor cap on it. This will not have much time, unless the leak is in your neighbor's business firm and he is not cooperative. Document the steps, and the results.
Install ferrite toroids or ready-made filters on all conductors going into or out of the device. Use higher permeability cores (75 or more) for lower frequencies and medium permeability (43) for 30MHz & up.
Amidon Inc. P.O. Box 25867 Santa Ana, CA 92799 Telephone: (714) 850-4660
Part numbers are: minor ferrite bead, number 75 textile, FEB-75B-101, $four.50 PK/12
Larger core unit of measurement, number 77 fabric, FB-77-1024, $2.00 EA
Very big cadre, number 77 material, FT-240-77, $nine.00 ea, (swell for cables)
Magnetic Properties of Iron Pulverization Cores
26 Xanthous/white Hydrogen reduced 75 825 dc - 1 Used for EMI filters and dc chokes
three Gray Carbonyl HP 35 370 0.05 - 0.l Stable, good Q for lower freqs
15 Ruby-red/white Carbonyl GS6 25 190 0.10 - 2 Excellent stability, adept Q
1 Bluish Carbonyl C 20 280 0.l - 5 Similar to Mix-iii, but better stability
two Red Carbonyl E x 95 two - thirty High Q material
seven White Carbonyl TH ix xxx three - 35 Similar Mix-2&6, just meliorate temp stability
six Yellow Carbonyl SF 8 35 10 - fifty 5.practiced Q & temp. stab. for 20-50 MHz
10 Blackness Powdered iron W 6 150 30 - 100 Good Q and stability for 40 -100mhz
12 Greenish/white Synthetic oxide four 170 fifty - 200 Skillful Q, moderate temperature stability
17 Blue/yellow Carbonyl 4 50 40 - 180 Like Mix-12, better temp stability
0 Tan phenolic 1 0 100 - 300 Inductance varies greatly with windings
There was some discussion of the effectiveness of various ferrite chokes a few days agone. I take access to a HP 4194A Impedance Analyzer, so I put a couple of popular ferrites through a swept-frequency impedance analysis. I measured 2 of Radio Shack's products:
the first is a cylindrical ferrite in a plastic holder, virtually 1.25 inches long by .75 inches in diameter. It opens upward like a clamshell and clamps downward on the wire. The opening is about 0.25 inches. The values shown are for a unmarried wire through the ferrite. FREQ INDUCTANCE ESR (Equivalent Series Resistance)
300 kHz 2.07 uH 0.073 ohms
2.iii MHz two.25 uH 6.9 ohms (the inductance peaks at this freq)
10 MHz 1.xviii uH 54 ohms
20 MHz 0.lxxx uH 89 ohms
40 MHz 0.50 uH 130 ohms
FREQ INDUCTANCE ESR
300 kHz 0.39 uH 0.044 ohms
2.iii MHz 0.38 uH 0.6 ohms
10 MHz 0.29 uH 7 ohms
20 MHz 0.21 uH eleven ohms
xl MHz 0.18 uH 10 ohms
One discussion of caution: Radio Shack is known for changing their product line at the drop of a hat, so employ caution in applying these measurements.
The easiest style to make a common-fashion choke is to have a ferrite toroid and wrap about 5-15 turns of the feedline onto the toroid, forming a coil. This will attenuate common-fashion signals nicely, without significant effect to the differential-mode signals Within the feedline (the desired TV signals in the case of TVI). For lower HF, #73, #75, #77 or J type material is best; for upper HF and VHF, #43 is a good all around material.
Beads must exist where leads enter the electronics box. Also treat the power cord and whatsoever other wires entering the box. If feasable, .001 mfd disc capacitors from the leads to ground on the box side of the ferrites will make the beads more than constructive.
ARRL has a telephone-interference package bachelor for download from our Web site, http://www.arrl.org/. If filters don't help, a ferrite toroid in the line next to the phone may work. Use as many turns as possible in the toroid.
To summarize, interference to non-radio devices is non the fault of the transmitter. The FCC states in their cloth that telephones that pick up radio signals are improperly functioning equally receivers. You lot may desire to help your neighbor observe a solution, but you are in compliance with FCC regs. Starting time, simplify the trouble. Disconnect all of the telephone devices. If you have an "RFI proof" phone, plug it in and effort it.
One such telephone is the Radio Shack model 43-591 phone for $xix.95 (less if on auction). This phone is highly resistant to RFI.
If it doesn't solve the problem, you lot tin take information technology dorsum to RS. For additional RF rejection, snip off 1 of the modular plugs that comes with the 6' cord, wind equally many turns as possible on a 1/2" ID, 1" long ferrite bead, and then reinstall the modular plug. If it works, you have determined that there is no problem with the lines or phone company equipment. Now, start calculation devices back to the lines 1 at a time.
VHF interference to wired telephones is not common, but it does happen. The use of indoor antennas does add to the problem.
In general, you will demand an RFI filter at each phone or affected device. In addition, yous may also need a split up filter for the handset cord, especially for frequencies most 14 MHz, or a ferrite core (virtually 10 turns should do) on the power-supply leads going to any of the telephones, answering machines, standalone modems, etc, especially for frequencies below 14 MHz. Many telephone filters are not constructive at VHF. K-Com makes one specifically for the VHF range. Contact: Yard-Com, PO Box 82,
Randolph OH 44265 Usa. Phone: 330-325-2110 Fax: 330-325-2525. Products/Services: FILTER-Telephone EMI FILTER :
Filter models RF-1 (modular), RF-ii (wired) and RF-1 Coiled String (for handsets). INSTALLING FILTERS INSIDE TELEPHONES You can homebrew a telephone filter using 470 micro-Henry chokes and caps having a value anywhere in the range of 1000 to 3000 pF. Insert ane choke in series with each telephone line (blood-red and green, most unremarkably.) Install i cap in parallel across the red and green lines, at each end of the inductors (full count is two inductors and two caps.) Yous can add together a second stage with two more series inductors and 1 more shunt cap in the middle of the network (total count is four inductors and three caps.)
There is considerable variation in RF susceptibility betwixt different models of telephones from the same manufacturer. I don't know of any make that is RF-proof without calculation an RF-filter or filters. Unfortunately, a few models of telephones are very susceptible to RFI and are sometimes almost impossible to RF-proof with an external RF-filter. If you recently purchased a highly RF-susceptible telephone, and you saved the receipt and all of the packing cloth, don't hesitate to return the phone.
Tell the store manager that telephones are non supposed to pick up radio signals-and enquire for a full refund. If the shop manager tells you that the interference is the error of the radio station, tell him that he needs to talk to an FCC engineer. This is the only manner that the manufacturers volition get the bulletin.
Radio Shack has a desk-bound/wall-phone that is much more RF-resistant than the average phone. The current cost is effectually $30. In many cases, they can be operated without a filter if minor interference can be tolerated. With a RF-filter, they are often RF-proof.
A phone RF-filter will perform best if it is placed inside the telephone, shut to the modular input jack. The input and output ends of the filter should non exist placed next to each other. They demand to be separated or the filter's power to attenuate common-mode RF will be reduced.
When opening a telephone instance, it is advisable to identify the push-button side of the phone downward on a table so that the buttons will not fall out when the case is opened upwardly. If the telephone'south input modular socket is wired to a printed circuit board, it will be necessary to cut the two traces on the excursion board. The filter may exist installed on the foil side of the board. The filter may exist mounted on the component side of the board past drilling #55 - 60 holes near the cut traces. Mechanically, mounting the filter on the component side of the board is best. Electrically, information technology makes no departure.
If y'all want to install the RF-filter outside the telephone, the filter can be inserted into the modular string betwixt the phone and the wall outlet. To identify the polarity of the wires, mark i side of the string at the area where it will exist cut. Make the cut about 6-inches from the modular plug at the telephone end and solder the filter in serial with the ii ends, taking intendance not to reverse the polarity. Exposed conductors should be covered with plastic tape or shrink tubing.
Some pulse-dialing electronic-telephones will not tolerate much capacitance across the phone line. In such cases, one or more of the shunt capacitors across the telephone line end of the filter can exist eliminated.
Wall-mounted telephones tin often be RF-proofed past installing a RF-filter in the wall outlet.
The pair of 470?H inductances {the components with the green-body and axial leads} work on common-mode RF. Sometimes, it's necessary to use a ii-section filter to increase the attenuation of common-style RF. To do this, connect 2 inductors in series, per side, with a tertiary capacitor across their midpoints, every bit shown below. If a two-section filter will not fix the problem, the telephone may exist acting like a cocky-contained RF-detector. To completely eliminate RFI, such telephones can be placed inside a shielded metal box, along with the person using the telephone. This is not very practicable, so the best solution may be to discard the telephone. One manner to examination for such a phone is to run across if it can observe the presence of RF without being plugged in!
If this is the example, the problem is self independent and an external RF- filter is non likely to assistance. Reportedly, a wooden stake and a hammer cures the trouble every time.
Telephone answering machines and portable telephone base units may as well require a ferrite separate-cadre RF-filter asphyxiate on their ability cords. This is washed by wrapping at least iv-turns of the power cord on the core. More than turns are usually improve. Ferrite split up-cadre chokes are sometimes useful as an external helper-filter for a phone that however has a small amount of RFI later on the internal RF-filter has been installed. Ferrite split cadre chokes {two per package} are available from Radio Shackr equally Snap-On Chokes, p-n 273-104.
Since it is possible for one RF-sensitive telephone to cause secondary interference to all of the other telephones on the same line, information technology is advisable to examination each phone individually for RF-susceptibility with all of the other telephones unplugged from the line.
This arroyo will assistance sort out the telephones that need help from the ones that are OK. This test should be repeated on each offending telephone after RF filtering is installed.
Princess and TrimLine telephones are ordinarily more difficult to RF-proof because the ringer is in the base unit, the dialing excursion is in the handset, and they are connected by the coil-cord which can human activity as a loading-coil/antenna. Thus, it may be necessary to install a filter on the phone line input wires most the modular socket on the base unit, and install another filter in the handset. Desk-bound type telephones, in which the dialing and ringer circuits are in the same enclosure, are unremarkably easier to RF-proof.
Loosely twisted phone wire splices in the wall or attic tin can contribute to RFI. The set up is to solder the splices or glaze them with silverish conductive paint.
If you lot have a telephone that receives interference on a particular band, even with a two-department filter, the phone may be at a RF-voltage-maximum in the telephone wiring. It may aid to RF-ground the telephone wires at the wall outlet with a pair of 50pF to 300pF equal-value capacitors. The capacitors are for tuning out the inductive-reactance of the footing lead on the troublesome ring. The optimum number of pF must be found experimentally. The best RF-ground is Non a ground rod driven vertically into the soil. This is the case considering HF energy tin can not penetrate more than than a few inches into the earth. A meliorate RF-footing is a horizontal conductor that is on or very near to the surface. All footing organization connections that are subject to wet should be soldered with 5% silver/95% tin solder. Often, an elevated 0.2-wavelength insulated counterpoise makes the most effective RF-ground. However, if such a counterpoise is connected to a ground rod at its far terminate, it becomes a high-Z RF choke.
Near all problems are common mode currents flowing between the CATV shield and the electrical outlet or long speaker leads. 99% of the bug were cured past grounding the CATV shield to the prophylactic ground of the electric outlet powering the TV or VCR. This provides a direct path effectually the Telly for mutual mode currents. F-CONNECTORS
Consumer-installed F-connectors on coax jumpers are another mutual path for RFI if the connections are non tight or if the connector is not crimped or screwed onto the coax tightly enough, or if it is completely missing and the center conductor is just stuck into the female connector! ANTENNA PREAMPS
Some thoughts:
i) Radio Shack Boob tube/FM amps are merely broadband amps with little protection from master overload. Commonly just a crude pi filter for hi-pass.I have found that cable TV class Channel Master and Jerrold are better engineered [more expensive, likewise!]
two) Wasn't at that place, now information technology is... Usually a proficient sign that there is a bad joint with corrosion in it, creating a diode rectifier/reradiator.
One of you may be the "proud" owner of a TV Translator station! Antenna maintenance is pretty well neglected by hams and unknown to the rest of the folks, but corrosion is a constant enemy of antennas and reception. I've even read of a concatenation link debate which did this! Y'all may accept to sleuth it like the powerline stories in this issue. Principal dominion: Only change one thing at a time. Don't go impatient and exercise a whole lot of things or yous'll be out in the side by side snowstorm doing it all again. Sound AMPLIFIERS
Information technology'due south quite likely that the audio amplifier is performing RF detection. You lot need to place ferrites on the speaker cables equally close to the audio output (right at the PC board if possible) with as many windings every bit possible. If it is audio detection, it won't matter at all how many ferrites yous install on the power cord or cable TV or antenna cable although this will cutting down on the amount of RF getting into the TV via those conductors. Direct pick-up onto speaker wires causes most problems. Don't get into the television if it is non your own. Unproblematic Mutual-Manner CHOKE
A very simple and constructive way to eliminate MOST cable RFI is as follows... Attach a 75-300 ohm balun to the incoming cable at the rear of the fix...take another 75-300 ohm balun, and ..attach the 2 leads to the two leads you just concluded upwardly with, and y'all are back to 75 ohms....this isolates the shield, which is the source of most RFI (common way). Top it off with a 75 ohm how-do-you-do-pass filter to the set up. Sounds uncomplicated, simply the baluns are ferrite torroidal and the hi-pass filter adds an extra measure of harmonic protection. All parts are available at Radio Shack and are inexpensive. Computer KEYBOARDS
In cases where the keyboard is picking upwardly RFI, at that place are several things you can endeavour, short of replacing the keyboard. The single clench-on beads are really not enough for 80 or xl meters. Get some FT-140-43 ferrite cores (Amidon, Palomar, etc), or other cores you lot KNOW to be ferrite that will work in the HF range and warp near ten turns of the keyboard cablevision onto a ferrite core, at both ends of the cablevision. This SHOULD make a pregnant departure, at to the lowest degree in the ability threshold that causes the problem. If you find it goes from 15 watts to 95 watts, for example, you are on the correct track.If it makes no deviation, information technology may be the wiring in the keyboard itself that is causing the problem. (This could also be true if information technology goes from xv watts to fifty watts, as an example: the problem could have a xv watt threshold on the cable pickup and a fifty-watt threshold on direct pickup.)
If it IS the keyboard, the easiest solution is to try another, such equally the IBM Spacer Saver keyboard, which has been reported to be relatively rf immune. You could too Effort some of the EMI shielding sprays available, trying to get a proficient shield inside at least most of the keyboard. You could too try a shielded keyboard cable, grounded at either the computer or the keyboard end, or both. Flat 1/2-inch braided strap is usually hollow and can exist used to shield your existing cable.If y'all do attempt sprays, try to ensure that both halves of the keyboard instance will be electrically connected to each other and to the keyboard-cable shield. And call back, these sprays are conductive paint; if the surface beingness sprayed is non clean and compatible with the spray, the paint could fleck off later, putting bits of metal flakes inside the keyboard. The gibberish on the screen volition probably return.
You may also desire to effort a simpler solution: Place a .01 mf cap cap across the leads at the terminal strip on the main unit of measurement. STOPPING Common SOURCES OF INTERFERENCE TO RADIO EQUIPMENT
resistor. The choke alone may be enough to clear upwards the problem in some cases. If these cures don't work, it may exist possible to shield the electronic switch module, but this must be washed safely!
Radio Amateurs who have been cursed with RFI from solid-state calorie-free dimmers will exist interested to know that at least one domestic manufacturer, Lutron, produces light dimmers that incorporate RFI suppression techniques. The Lutron NOVA series uses toroidal chokes that provide a significant level of RFI suppression, such as their model N-600, which volition handle upwards to 600 watts of incandescent lighting.
Another brand light dimmer produces an S9+ reading at 230 kHz (an arbitrary noisy frequency). The N-600, by comparison, produced a reading of S3, a difference of about xl dB. Absolutely, this is not zero, but installing the Lutron model should provide a reduction in RFI that is very gratifying. Night LIGHTS
Some nighttime lights with sensor optics tin can exist a source of HF hash. The offending light blazon is a CdS photocell, an SCR (or TRIAC) and a small incandescent lamp. When the light level drops, the thing switches on and off at a rapid rate and hashes up everything in the area! The lamp light will visually feed back to the photocell. In this design, the petty porthole for the photocell is removable. Take it out and cement a three/8 inch ID x ane inch long kraft paper tube in its identify to shield the photocell from the lamp light. This should prevent the feedback oscillation. You lot tin also look for better designs such as an electroluminescent deejay which plugs in, runs all the fourth dimension, draws about 12ma and shows nothing on a spectrum analyzer. They are supposed to have a minimum 10 year life and toll virtually $4. AUTOMATIC LIGHTS
Like to night lights, this is not uncommon to have a lite controller (photoelectric) cause RFI due to arcing. This is usually caused by inferior workmanship or component breakup causing a poor closure to the contacts. Offset affair to practise is introduce yourself and explain the difficulty. Explain the causes and if left unattended may crusade overheating due to the arcing. Eventually it volition neglect so why non put it out of it's misery and change information technology out? See if it's nether warranty. If it is, yous're home free just if isn't, feel out how he feels most changing information technology out. Many neighbors are willing to cooperate if given the gamble. LOW VOLTAGE LAMPS (Besides meet updates near bottom of article)
Some really strong broad ring noises have been discovered emanating from wall transformers powering various 12V consumer domicile interior lights. They are rated at an output of 12 volts at 60 Watts, which is a lot more current than a typically sized wall transformer usually puts out, and may exist solid state, SCR-based devices.
In this case, You will get no help from the FCC and very fiddling from the manufacturer. If you are on expert terms with the neighbor, you tin offering to replace the device with a UL rated wall mounted transformer (that is actually a transformer) if the output is ac, or a UL rated dc ability supply if it is dc. Another option is to buy him a like, but higher quality lighting organization and trade with him. Pay an electrician to install information technology unless it will just plug in. The cost is probably less than $100 and it will certainly make your life more livable. DIGITAL TEMPERATURE DISPLAYS In ane example, a faulty digital "Quadra-Temp" temperature readout for a solar water heating system became a broadband RFI generator. COMPUTERS Computers can generate various birdies leaking from all cables. Strong broadband hash tin can be generated by the switching ability supply. This hash is non affected by unplugging all cables from the PC. The root cause of this problem is that at that place is supposed to be a line filter in the PC board in the power supply, just it's usually only jumpered through with bus wire (tin you say, make 'em cheaper?). Yous'll have to open the supply, so you'll probably run into the footprint on the PC board where the filter should have been. If you lot have a small ferrite core, take a pair of wires from a four-wire telephone cable, twist them together and made a bifilar winding of as many turns as y'all can on the ferrite core. And then install this in series with the jitney wires. In i case, this reduced the noise past 30-40 dB.
Apropos RFI from PC to HF it is the need of stopping the rf catamenia and consequent radiation, forth the interconnecting cables to outboard devices. The about applied manner to do it is to keep 'em short, and placing chokes as close every bit it is possible to their ends where they enter the computer. To realize effective chokes in few turns it is a need to use materials whose permeability is very high, 2000 or more.
Switching to a metallic case is besides effective.
Endeavor installing an Air conditioning line filter on the computer ability string to solve spontaneous re-kick problems. The RF can get into the Ac wiring and extension cords laying on the basis.
Replacement of the a.c. input connector with a filtered type is an easy 1-hour job, start to terminate and information technology will probably get rid of 95% of your problem. For the rest you might want to play with snap-on chokes.
The mounting hole for the connector must be widened a few millimeters on each side--something that can be done with a file in a minute or two. Only make certain in that location is enough room behind the connector position to articulate the somewhat longer RFI filter. In some cases, you may need to bend a capacitor out of the way.
Check anything else continued to the Tv. If no change then the path is direct radiations from the TV and shielding is required. A coax cablevision from your receiver terminated in a pocket-size one turn wire loop can snoop (cautiously) effectually the Goggle box chassis to find the source. Apply shielding to that area (cautiously and not-shorting). [ADD a i:1 Balun at your antenna]
If your ownership a TNC, get one with a metal case. If you have i with a plastic instance, attempt roofing it with foil or placing it inside another metal instance or box and bonding the foil or box to your station ground. AUTOMOTIVE SOURCES
They offer a fuel-pump filter that installs in the tank, right next to the in-tank fuel pump, which, if not covered by warranty, is a real pain to install, and may non work if y'all accept a non-metallic fuel tank. The part number for the filter is F1PZ-18B925-A and may cost up to $60. A cheaper and much easier solution that some take had success with is to wind BOTH power wires going to the fuel pump around ferrite cores. Electric FENCES Cheque all the connections on the transformer to exist sure they are tight. A poor or broken grounding conductor at the transformer box is a likely culprit. Check all standoff insulators for cracks, and make sure the wires are non touching anything except insulators. Inspect the nails property the insulators to posts or trees. Walk around the debate at night and mind and look for sparks to indicate problem spots. Weeds and branches from bushes and trees touching the wires is too a common trouble.
Eliminate or refresh poor splices in lines. If the fence belongs to someone else, offer to perform the repair work yourself.
Hither are some more points suggested past i electric fence manufacturer:
ane) Brand certain the wire feeding the fence is insulated for 20K volts. Romex or other wire, not intended for this use, tin can arc if information technology gets close to anything else.
two) If in that location are splices in the wire, make sure the two sections are connected with a compression clamp sold for that purpose, and try to avoid mixing types of wire. Soldered and twisted connections are not recommended either.
three) Some nail-on type insulators accept very, very little insulation between the boom and the wire. Supervene upon them with good nail-in insulators made for electric debate employ.
four) If at that place is much RF beingness generated, a iv,000-volt charger, for case, probably isn't delivering 200 volts to the fence.
Interference ever indicates something wrong that will reduce the voltage, and the efficiency, of the fence. This may help convince a contend owner to let y'all inspect the contend. TRACING Electric line NOISE
THIS PORTION OF THE ARTICLE IS FOR INFORMATIONAL PURPOSES Simply! Practise NOT Effort Whatever Physical CONTACT WITH Power line EQUIPMENT INCLUDING POLES OR GUY WIRES TO LOCATE SOURCES OF RFI!
Leave THIS TO THE ELECTRIC COMPANY. IT IS THEIR RESPONSIBILITY.....Non YOURS!
ASSIST THEM ONLY WITH TRAINED Power Visitor PERSONNEL SUPERVISING YOU.
Do Not Effort STATEMENTS IN RED IN THE Commodity Beneath Concerning ELEVATED Power LINES!
ELEVATED POWER LINES
You volition take good success using a inexpensive aircraft band portable. 108 to 136 MHz aircraft communications uses AM and so receivers for that band have AM detectors. Line dissonance is much shorter range on VHF so you normally have to be much closer to a noise source to detect it. My all-time results was with a home-brew tunable HF am detector only the aircraft band receiver is almost as good. What you are looking for is loose hardware on the poles.
You can spot slack bells quite hands since they usually sag under their own weight. If the line they are on was properly tensioned, they wouldn't sag. Bong insulators are supposed to have metallic spring clips or soldered on jumper wires to prevent
arcing simply occasionally these things are damaged and no longer brand contact.
Another common source of pole superlative arcing is just loose hardware. Any kind of metal-to-metal contact, such as nuts, bolts, brackets, and braces, tin loosen from the compress and swell of poles with weather changes. When loose, oxide layers build up and arcing begins. Even though non straight connected to the power lines, these arcs tin be then powerful that they couple into the line and propagate for miles. Information technology is not uncommon for loose nuts and bolts on a pole tiptop to loosen and arc so badly that the pole catches burn. Obviously, noise that goes away when the poles are wet and comes back when the poles are dry is a good candidate for loose hardware issues. It is a common task for a line maintenance crew to tighten hardware on pole tops.
Transformers are rarely the source of line noise. I actually found but one noisy transformer and information technology was just a loose loftier voltage connectedness to the pinnacle of the transformer.
Racket burst were produced as the wire wobbled. What y'all practise to locate a bad pole is to first narrow the search surface area downwards to a few poles. Carefully inspect the poles with binoculars for obvious loose or broken hardware. And so lightly kick doubtable poles to encounter if the noise is changed or modulated by pole vibration. Unless the base is actually stout, simply turn your back to the pole and give it a mule kick.
Some louder sources could ravel several miles on the lines though. If yous are having trouble narrowing the search down, try another fox. Go to a convenient pole guy line and gently wiggle information technology to get the ability lines to beginning swaying a niggling.
THE IMPORTANT THING TO REMEMBER IS DON'T Affect POWERLINE EQUIPMENT E'er. Be SAFE Not DEAD!
Sometimes, loose hardware on a conductor run would show upwardly from the line move. One affair to spotter out for, aside from the obvious danger of just being around power lines, is that y'all are not fooled by the noise peaks yous volition notice nigh pole footing lines, guy lines, and other conductors running down poles. These things bring electric line noise right down to you so might make yous retrieve y'all have establish a source when all you lot take is a dissonance antenna.
Exit 1 nighttime night and walk along under the lines and listen by ear too as radio and spotter carefully at each pole. If at that place is a leak across an insulator (commonly a cracked insulator) it may have a visible arcing.
++++++++++++++ A skillful tool to detect electromagnetic energy is a phone installer's inductive probe tool, such every bit those available from Progressive Instruments. They literally produce an audio output of whatever they notice, with no translation (1:i). This ways that if you have a conventional telephone line, you lot can hear the chat (not quite clearly though) by activating the tool and holding the probe end against or near the line. The proceeds on these tools is variable, so you can set your gauge threshold for reception. In terms of interference acquired by computer equipment, I'll add together another good few items to your list. Cable Modems are peculiarly bad in terms of interference. I've heard from a few shortwave operators or listeners mutter about interference in the 20-40 khz range. What y'all are hearing is the up aqueduct on your modem! You can frequently asking that your cable operator move your service to a different aqueduct (there are multiple shared up and down channels for both upload and download, with download usually beingness +800MHz. HPNA tin can go either fashion, lots of interference, or no interference. It's a more than or less worthless technology anyway though. It'southward far from fast, and cannot compete with 802.11g wireless, either in speed, or in ease of operation (and ease of unplugging if it DOES interfere!) Ethernet switches tin can exist an badgerer as well, producing noise from 10MHz to 350 MHz, depending on the speed of your network, and if y'all take multiple concurrent speeds, racket on multiple frequencies. LCD monitors tend to produce more interference than CRT units, due to the inverter lath that operates the fluorescent element in their backlights. These things can run at 7-800 volts at (sometimes multiphase) frequencies of around 400Hz. Some models are coming to market with LED based backighting, which should finer eliminate this trouble. UPS units can cause a lot of interference, especially when they go into their fast charging modes when regenerating after an outage. I have a rack of APC SmartUPS 2200s, each with a secondary battery pack attached. I can run all of my equipment for more than than two days with no line AC, and they use a very nice stepped modified sine moving ridge output, which most radio equipment actually can live with very well, though when they boot the charging into loftier gear, my shortwave is effectively useless if on the same circuits. Information technology works ok running off of their batteries though. Square wave (RMS style) UPS's are garbage. If you think yous tin take a 500 watt line interactive UPS for less than $200, you don't deserve one. Home security systems are as well a cause of annoyance. They oft use a very high voltage serial interface (12 volts!!!!) which tin can make your AM radio not piece of work well at all, frequently extending upwardly to around 4 MHz. Don't forget that incidental RF emissions from series communication equipment (even a computer serial device can count) can be found at frequencies several MHz (or several times in fact) higher than the operational frequency of the device. Regards UPDATES AND MORE INFO
Nathan Karras
N Systems Technologies
Admittedly, I am not an operator of apprentice radio (presently), though I do listen to shortwave. I've been in the procedure of reading everything I tin can become my hands on about shortwave and VHF communication for the last week or and then. I do, however, bargain very oft with microwave and UHF advice links, and with ethernet and like "near-rf" cabling systems.
The last thing I can remember of now is my subwoofer amp. It's built into the sub (Home theater equipment, not auto crap), and when information technology starts, there is an audible hiss at around i-4.five MHz, here and at that place, not all the way across, until it turns itself off (or is unplugged).
Nathan Karras
N Systems Technologies
IF YOU Accept VALUABLE HELP, HINTS, TIPS OR TRICKS TO GET RID OF RFI, PLEASE LET US KNOW VIA OUR E-mail ADDRESS . WE WILL Exist HAPPY TO Add together THEM TO THIS Folio! From: Mike OH2FCZ 03-2014
LED strip lighting may crusade RFI due to the long run of LEDs radiating whatsoever problems in the (oft cheap) switching mode power supply. Wrapping the supply lines effectually a ferrite core may aid mitigate the trouble. Mobile phone & tablet chargers should also be treated with suspicion.
LINKSYS ROUTERS AND PRODUCTS GENERATING RFI!
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Is There A Plug In Filter To Reduce Line Interference On My Garage Workshop Radio?,
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