(Now a bi-weekly program)

November 13, 2012

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RFI Detective

Overview   

In this episode #43 we discuss the topic of finding and eliminating local sources of noise that interfere with signal reception and trying to mitigate them. The basic process is to first try to characterize what the noise characteristics are then to use fairly standard troubleshooting techniques to identify the source(s) and to describe the measures that can be taken to lessen or eliminate the noise. And per usual, we have a great set of references for further study, and a "project" that you can build and use in the shack or around the home to locate troublesome interference.

73, George N2APB  & Joe N2CX

Audio Recording ... (Listen to the MP3 podcast)

Discussion Notes:

<20:14:15> "Ray K2ULR": The K9YC paper is a classic.
<20:19:09> "George - N2APB": Which is the K9YC paper Ray?
<20:36:53> "Ray K2ULR": That's the Jim Brown paper.. Web link #1. Should be must reading for all hams.
<20:37:32> "Joe N2CX": K9YC piece is the auudiosystrmsgroup paper
<20:39:46> "Joe N2CX": spelling doesn't count....
<20:43:22> "Ken - VA3KMD": Does leaving the cable ground connections intact but adding a parallel wire to the power supply input ground create a ground loop?
<20:44:44> "Joe N2CX": That's why the internface box folks using internal xfmrs make a fortune
<20:45:41> "Pete - WB2QLL": You can buy ground loop isolators at any place that sells automotive audio, including Walmart.
<20:46:31> "Clint-ka7oei": My PTT didn't work
<20:47:02> "George - N2APB": Ahhhh, NP. Glad to have you with us tonight!
<20:52:09> "Mike WA8BXN": Is RFI radiation from DSL on ih house phone lines much of a problem?
<20:52:40> "Howie - K3HW": I use a mechanical hand-wound clock (yes! with gears and a main spring) in the shack to eliminate square wave clock signals which generate harmonics.
<20:52:51> "George - N2APB": I've not heard of this happening Mike ... But it might be.
<20:53:38> "George - N2APB": Yeah, even clocks, Howie, could indeed cause problems if too close to the radios.
<20:58:21> "Joe N2CX": Plasma TV's are yet another source of horrendous noise!
<20:58:33> "Milt-W8NUE": Amen
<20:58:39> "Joe N2CX": ON4WW
<20:58:57> "Alan W2AEW": I've got a plasma TV in my next door neighbors - horrible on 40 and 75m
<20:59:45> "Alan W2AEW": once tracked down a bad insulator on a utility pole using a shortwave receiver. Verified it was on the pole by whacking it with a baseball bat
<20:59:55> "Joe N2CX": Tell 'em they cause cancer so replace with an LED version...
<21:02:11> "Mike WA8BXN": 40 meter fox hunt starting, 73/72
<21:02:15> "Milt-W8NUE": Alan, whacking with a bat or hammer is frowned upon. Something is wrong with the pole and might come down when whacked!
<21:02:20> "Joe N2CX": Yet another $$$ sniffer application at: http://www.tmworld.com/design/failure-analysis/4389545/Can-a-129-spectrum-analyzer-be-any-good-
<21:02:50> "Joe N2CX": At least when the pole comes down the noise will stop!
<21:03:13> "Clint-ka7oei": MPSA18, 2N5089
<21:03:19> "Joe N2CX": 2N3565 is a good low nooise audio transistor for the TAPIR
<21:03:41> "Ken - VA3KMD": Someone should bring back the Sniffer kit!
<21:04:29> "Milt-W8NUE": Radiated noise from power lines is best tracked at VHF/UHF. At low frequencies the noise can not be easily located.
<21:05:05> "Clint-ka7oei": I use a telephone "sniffer" (the other end of a "toner") for this sort of thing... It's just a JFET (hi-Z, grounded source) in front of an LM386...
<21:08:53> "Lee KM4YY": The TPAIR kit appears to be sold out.
<21:09:04> "Lee KM4YY": Tapir'
<21:12:02> "George - N2APB": Yeah, Elektor often goes out of stock with their kits. Perhaps they'll soon have it again - they don't too often dsicontinue things. Or, perhaps put a WTB posting to the lists in hopes that someone wants to part with thiers.
<21:13:18> "Clint-ka7oei": It's always good to use the "AM" mode when using a receiver to find noise!
<21:14:01> "George - N2APB": Why?
<21:14:59> "Howie - K3HW": most noise is amplitude based
<21:15:07> "Clint-ka7oei": You beat me to it!
<21:15:39> "Howie - K3HW": sorry Clint - you have the floor!
<21:15:40> "George - N2APB": Outstanding comment Milt. For the record: Run the Rx audio into a spectragram program to better understand the characteristic of the noice.
<21:15:45> "Clint-ka7oei": If it's amplitude-modulated white noise, the 60/120 Hz component may be entirely missed unless on AM.
<21:15:46> "Joe N2CX": Alos the AM mode in most receivers is wider band!
<21:15:50> "Clint-ka7oei": No prob - saved me typing!
<21:18:41> "Clint-ka7oei": I solved that problem with 100 ohm resistors on the clk/data leads - with 100pf caps on the equipment (not cable!) side of the NUE/KBD.
<21:19:19> "Clint-ka7oei": (100 ohm resistors are 100 ohms at almost any frequency - unlike clamp-ons)
<21:20:32> "George - N2APB": Very good approach.
<21:22:56> "Howie - K3HW": Was able to key a 220 MHz FM Repeater with my HT in the control room of a diesel submarine with all hatches closed which you would think mimics (sp) a FARADAY Shield. My signal was being reradiated via coaxial cables passing through watertight hull penetrations.
<21:22:57> "Ray K2ULR": That was the issue for me... FT-817, Buddipole, NUE-PSK modem all within 10-15 feet
<21:24:09> "George - N2APB": That's amazing Howie. What power level in those instances?
<21:24:09> "Joe N2CX": I'll bre a balun at the Buddiepole feedpoint would keep RF off the coax shiled and lessen self-interfnerence.
<21:24:44> "Joe N2CX": That is I'll be, not I'llbre...
<21:25:09> "Milt-W8NUE": Our local power company is ususally eager to find bad insulators. With our drought condx, fires are common.
<21:25:19> "Joe N2CX": Om an, I meant I'll bet!
<21:25:37> "Ray K2ULR": Buddipole has a series of chokes ("balun") as part of the normal setup.
<21:26:38> "Joe N2CX": Ah, now they ahve learned their lesson. Early ones had no chokes.
<21:27:11> "Howie - K3HW": A 2 watt 220 MHz HT. The NOSC Engineers (Naval Ocean System Center) in San Diego surmised re-radiation via the coaxial cables through the hull penetrations and up to my antennas... USS Dolphin SS-555, she is a museum boat now in SD, CA.
<21:27:47> "Howie - K3HW": I was the comm officer/radioman at the time - My Commanding Officer was a Ham too!
<21:27:57> "Milt-W8NUE": Must go. 73 guys!
<21:31:00> "Armand WA1UQO": Great show again guys! Thanks for all the effort. BTW - Great teamspeak picture Alan! Gotta Go - 73


SESSION NOTES ....

  

Identify type of noise

          Frequency

          Identifying Characteristics

                   Listen

                             Compare sounds from ARRL site

                             URL <http://www.arrl.org/sounds-of-rfi>

                             Has audio of interference from:

                                      Household Appliances and Electrical Equipment.

                                       Computers and Computer Peripherals

                                      Transmitters and Intentional RF Emitters

                                      BPL, Line Noise and Industrial Equipment

                                      Miscellaneous equipment

         

 

Getting rid of RF riding on "zip cord" being used as speaker wire

 

 

Try to identify the interference source

          Turn power on/off various equipment in your house

          Does it vary with time of day

          Sniffing around the house or neighborhood

                   Use a good HF portable device like the FT817

                             E field noise can be received and located by using a short

                                      whip (~ 1-ft) right on the rig

                             H field can be traced down by using a coax cable connected

                                                to the rig's antenna jack with a 2-3 turn 2” dia. Loop.

          Try to track the interference to its source

 

To: FT817@yahoogroups.com
Subject: [FT817] Using your FT-817 to help locate sources of RF noise

Hi all!

I've found that among other things, the FT-817 makes an excellent portable receiver for locating RF noise sources. I've used it on at least 3 occasions for this, and easily located the offending source each time. Here's what I did:

Hook up a small rubber-duck style antenna to the front (BNC) connector on the radio, using a short and well shielded coax cable. I used a military surplus male-to-male BNC cable, about 24" long. One end connects to the radio, the other to a female-to-female BNC adapter.

The antenna also has a BNC connector, and so connects to the other side of the female-to-female adapter.

The antenna which I use for this is the stock antenna from an Alinco model DJ-580 dual band HT. You could also use the stock FT-817 antenna, but I've found it easier to localize noise sources with the Alinco antenna due to the smaller size.

Set up your FT-817 to operate from internal batteries, and away you go. I've found that you can locate most noise easily by tuning the radio to somewhere in the aircraft (118-136mhz) band, using the AM mode.

Then, walk around with the radio and antenna combo, while using the antenna on its flexible cable to "sniff" for noise. As you get closer to the noise source, you can run the antenna very close to the item (s) in question.

The neat thing about this is that since the FT-817 has such wide frequency coverage and good receive performance, along with a signal-strength meter, it can be most helpful in tracking down both wideband and frequency-specific noises. But, I'm not sure that it would work well within a high RF environment, such as a broadcast site.

Anyway, hope someone finds this useful. Take care and have a great
weekend!

- Darrell/KA7BTV


 

 

 

Steps to eliminate noise sources

          Change antenna location/orientation

          Increase physical proximity from the source

          Try different antenna cable locations or orientations

          Bypass and/or filter power and signal cables at both the interferer or your rig

          Use ferrite chokes (snap-on type) on power and signal cables

          Use choke baluns on your antenna feedlines at the antenna end

 

HRO RFI Filter                                      Power Strip with RFI Filter                            

 

 

 

 


RFI “Cases” and Sample Sounds … http://www.on4ww.be/emi-rfi.html

From the very informative and entertaining pages of ON4WW.  (Content greatly reduced here … view original web page for complete stories!)

 The 'AL BUNDY' case
Shoestores. No more, please. It took me two years to solve this one. The RFI was caused by a defective high voltage part of neon lighting at a shoestore.  This is how the RFI sounded like. It took out the whole 80m band. A second and longer soundclip is available, on which the RFI is much less distinct in strength than the interference on the first clip. That is because when the lighting was switched on, it took a while for the 'sparks' to get completely active (and become more dangerous in regard to fire hazard).
With special thanks to our Telecom services for a job well done to bring this case to a good end. 

The LATOYA NIGHTCLUB incident
This anomaly occurred during the cold wet winter months, with sparks clearly visible on the roof. Had this happened during the previous hot summer, who knows what could have happened. Another fire prevented? Here is how it sounded like at a distance of 1.5 km.

The faulty FREQUENCY CONTROLLED DEVICE at a big sportscomplex
Half December 2009, a terrible interference popped up on my southwest beverage on the 160m band.  Click
here to view the video. First you will see and hear (AM mode) the Yaesu FT-817ND radio picking up the intermittent interference sound, while a relay clicks away in the background. After the camera zooms in on a relay; you can see the I/O switch rocking sideways (sorry for the blurred quality, the macro function was not enabled).
This interference sound was 2 kilometer away from my Beverage antenna, and loud! It was audible on 1816-1832-1845 kHz-etc. On this soundclip you can hear how it sounded at my station, at 2 km distance!
It took 3 evenings and a complete shutdown of the sports and cultural complex to locate this electrical malfunction. At first we thaught the industrial relay, labelled C5 on the picture to the left (click to enlarge) was at the origin of the RFI. However, once this relay was disabled, the RFI continued. It seemed the frequency controlled device that steers the large heating system of the sports hall, was at the basis of this anomaly, and this assumption was proven correct later on.
Notice the blue wire (relay point nr. 4) shows a shade of black, which may indicate this wire has heated in the past. Due to the malfunction of the frequency controlled device?  Here is a video on which you can just see the green LED go off as the RFI stops.

Faulty STREET LAMP at ON4UN
February 2010. John ON4UN calls me for an inteference source hampering his reception on the 160m band. It turned out to be a faulty street lamp.  Here is a
video on this type of interference. You will see the blue backlight of a Yaesu FT-817ND radio, the dimmed street light during interference sequence (ignition), and the disappearing of the interference once the lamp gets activated. Here is another video, taken inside John's shack. You can hear the interference on the K3 radio, and at the end it drops off (when the lamp gets activated). The radio is in AM mode..

The TUNNEL case
Late 2004, my reception towards JA on 160m was hampered by a barely noticeable raised noise level. Just enough noise, when intermixing with the ever so weak JA-signals, as to make it impossible to make out callsigns.
 On this
soundclip you hear me talking in Dutch, announcing the monitored frequencies on an AM receiver. In this order, you can hear the RFI on the following frequencies: 3.5 MHz, 1.8 MHz, 168 kHz and 7 MHz. In between 168kHz and 7MHz you can hear me cleaning my boots before re-entering the house.

The TRAIN case
Working on topband means working night shifts. And early morning shifts, just before the sun gets up. My first years with beverage antennas, opened up a whole new world. Not only in being able to work new ones, but in being able to detect all kind of man/machine made noises. The first beverage-years, I often noticed this annoying noise early in the morning. I couldn't pinpoint it, it came and went, on different headings. I listened often to this sound (in AM mode), and because of that, I immediately recognized the same sound while watching a train go by in 'The TUNNEL case'... mystery solved! Here is a
soundclip of a train passing by... at 1 km distance! Think I made this recording in AM mode, on CW it sounds not as distinct but is still pretty annoying. I can more or less follow the train on my beverages... usually starting on south heading, going over southeast and east, and finally disappearing on northeast.

The CONSTRUCTION CRANE case
Here is a
soundclip of the first ever RFI-construction crane I encountered. You will understand that it is impossible to copy any weak signal on topband with this type of heavy interference. Distance from antenna to crane is 1.6 km.
Can it get worse? Here is a soundclip of two construction cranes hampering my reception on topband simultaneously!
The icing on the cake comes in this soundclip: a construction crane operational at 2 km distance and a train passing by at 1 km distance...all at once...wonderful!

SNOW STATIC
Well, we can debate if this is RFI/EMI or not, but it sure makes a lot of noise. You can often hear this on yagi antennas, but also beverages are prone to it. Can be induced by snow, hail, even dry cold air. This kind of interference is one of Murphy's favorites during the CQWW contests... here is a soundclip.

The FLUORESCENT TUBE LAMP case
This was an easy one. In 2003 I bought a couple of fluorescent tube lamps to be installed in my new shack. They are ignited with an electronic starter. On this video you can witness the result of a badly engineered fluorescent tube with electronic starter, causing heavy RFI on 28 MHz. Distance from the 28 MHz antenna to the lamp is 25 meter. If anyone has an easy solution for this one, let me know pse (yes, I know I should get a conventional starter).

The Samsung PLASMA TV case
For some years I had an annoying interference that was centered smack in the middle of the 80m (75m) SSB DX window. As I was not very active on 80m in those days, I didn't immediately tackle the problem. November 2004, it was time to take out the bike. I located the RFI source in a used car sales shop. The RFI was caused by a Samsung plasma TV, model P2. It was continuously on during daytime and late in the evenings. The RFI at 800m distance was noticeable at 200 kHz intervals. When close to the TV with a portable receiver, it was noticed that the TV radiated non-wanted signals from LF into VHF spectrum. Waw. The RFI on the soundclip, is recorded first on LSB, then AM mode, and back on LSB at a distance of 800m.

The da-di da-di case (solar panel inverter)
Although this is not a typical RFI source, it can be very annoying and is indeed interfering when listening to weak signals on the 80m and 160m bands. A 10 second tone is followed by 7 seconds of two different alternating tones. These signals were first heard in 2009. ON4UN,  This recording was made at a distance of 1 km. Some people may think it is the Hyperfix signal (heard in western Europe below 1825 kHz), it is not.

The FLUORESCENT TUBE LAMP case
This was an easy one. In 2003 I bought a couple of fluorescent tube lamps to be installed in my new shack. They are ignited with an electronic starter. On this
video you can witness the result of a badly engineered fluorescent tube with electronic starter, causing heavy RFI on 28 MHz. Distance from the 28 MHz antenna to the lamp is 25 meter. If anyone has an easy solution for this one, let me know pse (yes, I know I should get a conventional starter). 

The Samsung PLASMA TV case
For some years I had an annoying interference that was centered smack in the middle of the 80m (75m) SSB DX window. As I was not very active on 80m in those days, I didn't immediately tackle the problem. November 2004, it was time to take out the bike. I located the RFI source in a used car sales shop. The RFI was caused by a Samsung plasma TV, model P2. It was continuously on during daytime and late in the evenings. The RFI at 800m distance was noticeable at 200 kHz intervals. When close to the TV with a portable receiver, it was noticed that the TV radiated non-wanted signals from LF into VHF spectrum. Waw. The RFI on the soundclip, is recorded first on LSB, then AM mode, and back on LSB at a distance of 800m. 

 


THE PROJECT ...   Elektor Tapir Sniffs Out Electro Smog ... http://www.elektor.com/news/elektor-tapir-sniffs-out-electro-smog.2200626.lynkx

 

 

 

Do you worry about electromagnetic pollution? Wireless is cool, especially because it works without wires. On the other hand, Wi-Fi, Bluetooth, Zigbee, broadcast radio & TV transmitters, mobile phones and a plethora of electronic gadgets and instruments with base stations on every roof are polluting the electromagnetic environment in which we live. Is this pollution harmful for living organisms or not? Nobody really knows.

 

Does this worry you? Do you wonder how dirty the ether that surrounds you really is? Then the Elektor Tapir is what you need. A tapir is a large browsing mammal, similar in shape to a pig, with a short, prehensile snout. The Elektor Tapir is a small electronic device, similar in shape to a cigarette lighter with an antenna. It comes as a complete kit including two types of electromagnetic detectors and earphones. Sturdy and easy to build, the Elektor Tapir will sniff electro smog of almost any frequency.

 

Kit of parts available at a special low price. 

The Tapir PCB is sponsored by Beta Layout allowing us to sell the kit of parts at a ridiculously low price of only 13.30 / € 14,95 / $21.50!

 

 

 


REFERENCES

  1. ARRL RFI book – ARRL bookshop

  2. Elimination of Electrical Noise – RSGB bookshop

Articles

  1. <http://www.arrl.org/files/file/Technology/RFI%20Main%20Page/Hallas.pdf>

  2. <http://www.arrl.org/files/file/Technology/RFI%20Main%20Page/InterferencePrimer.pdf>

Web Links

  1. <http://audiosystemsgroup.com/RFI-Ham.pdf>

  2. <http://www.incompliancemag.com/index.php?option=com_content&view=article&id=739:using-ferrites-to-suppress-emi&catid=26:design&Itemid=130>

  3. <http://audiosystemsgroup.com/publish.htm>

  4. <http://www.on4ww.be/emi-rfi.html>

  5. <http://www.gare.co.uk/noise/index.htm>

  6. <http://egpreston.com/westinghouseduetrfi.htm>

  7. <http://www.w0qe.com/RF_Interference/grow_light_electronic_ballasts.html>

  8. <http://www.radioing.com/eengineer/glossary.html>

  9. <http://www.lutron.com/applicationnotes/360484.pdf>

  10. <http://lutron.com/nova/?s=17000&t=17200>

  11. <http://www.v-soft.com/ZipSignal/zip_answer.asp>

RFI Enforcement Pages

  1. <http://www.arrl.org/FCC-Enforcement-Activities-and-the-Electric-Utility-Industry>

  2. <http://www.arrl.org/part-15-letters>

 

FCC Enforcement News and Web Links

  1. <http://www.arrl.org/news/fcc-to-utilities-don-t-look-to-hams-to-pay-for-your-testing>

  2. <http://www.arrl.org/news/FCC-Issues-Citation-to-Part-15-Marketer>

  3. <http://www.arrl.org/files/file/Technology/news_20070830100.pdf>

  4. <http://www.arrl.org/files/file/Technology/news_200606081.pdf>

  5. <http://www.conformity.com/enews042006/Article2.html>

  6. <http://www.conformity.com/enews030906/Article1.html>

  7. <http://www.kcbd.com/Global/story.asp?S=6990655&nav=menu69_3_10>

  8. <http://www.kcbd.com/Global/story.asp?S=7122987&nav=menu69_3_9>

  9. <http://www.arrl.org/files/file/Technology/RFI%20Main%20Page/lubbock_2.wmv>

  10. <http://www.arrl.org/files/file/Technology/news_200108211.pdf>

Information for Electric Utilities

  1. <http://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/ucm106367.htm>

  2. <http://www.rsgb.org/emc/>

  3. <http://www.narte.org/h/captcha.asp?pagename=emcconsults.asp>

  4. <http://www.ce-mag.com/archive/03/ARG/emc_standards.html>

  5. <http://www.radioing.com/eengineer/index.html>

  6. <http://www.ofcom.org.uk/static/archive/ra/topics/research/RAwebPages/Radiocomms/index.htm>

  7. <http://news.com.com/2100-1033_3-6199149.html>

  8. <http://www.aerorfi.org/>

Naval Postgraduate School RFI Handbooks

  1. <http://www.arrl.org/power-line-noise-mitigation-handbook-for-naval-and-other-receiving-sites>

  2. <http://www.arrl.org/files/file/Technology/RFI%20Main%20Page/Naval_RFI_Handbook.pdf>

 


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