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Old 01-11-2008, 10:41 AM   #1
Andy N1ORK
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Default RFI from power converter.

Hi to all! Since I am new to this great site, I thought I may get some help with a problem I'm having.
I'm getting a lot of interference in my Crossroads Zinger camp trailer from my WF-8955AN w/Plastic power converter installed in the camper. It seems to be coming from the 12VDC lighting, as I am able to affect the interference by turning different lights on and off, thereby affecting the output load. Even with all the lights off, I still hear the RF noise (RFI). It happens on all the HF bands (1.6 through 54 MHz) with about 5 to 6 S-units of noise and the frequency drifts about 10khz back and forth over a period of about an hour.

I am using a Yaesu 857D all band Ham transceiver with a di-pole antenna hung in the trees outside my camper. My radio is grounded to an 8 foot outside grounding rod, but this did not help.

I need help in eliminating this RFI noise issue. Does anyone know of or can anyone recommend something to cancel out the noise? Maybe a torroid choke or something like it connected at the DC output or at some other location. I plan to try .01mf caps to ground at bothe ends of the DC wiring when we go back to the camper later this year. I tried contacting the manufacturer, wfcoelectronics.com, but no reply from there. Any help will be appreciated.

Thanks and 73
Andy - N1ORK



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Old 01-11-2008, 10:49 AM   #2
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See also "Electrical Noise" in the "RV Systems" forum
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Old 01-11-2008, 11:03 AM   #3
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Default Thanks for the info!

I see I'm not the only one with a problem. It's too bad ther's no easy way to get back at the manufacturer to provide a fix.
Thanks again!



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Old 01-12-2008, 12:29 PM   #4
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There are two types of lights commonly used in RV's Incandescent and florescent

If the RFI occurs only with the Florescent lamps then I'd suspect the solid state "Ballast" in the lamp as opposed to the converter If it is worse with the Incandescent then I'd suspect the converter.

Several years ago QST had an article on TVI ... The took a cheap portable TV and during one of the W1AW scheduled transmissions turned it on and looked for the station which had the worst picture. IT WAS A MESS, no usable picture at all 100% noise (Remember you are close enough to W1AW's antenna farm to throw snowballs and hit them)

Then they took the same TV, put it in a Farday cage they had built with bandpass filters on the antenna and power leads (low on power, high on ant) and the picture was 100% there, no problems at all.

In this case I'd suggest that you not put your receivers in such a cage but rather the converter, Use a brute force filter on the 120 volt side (Any good filter should do) right where it enters the "Cage" and use a stack of bypass capacitors on the output where it goes through the cage,, .1 .01 .001. .0001 Micro Farad Perhaps 2 or 3 stacks all in all

I'd not suggest chokes at this point unless they are the ferrite bead type (no coils, just beads) Make sure the cage has lots of vent holes (use screen not sheet metal) so the converter can breath and get rid of excess heat... A "HOT" converter is not going to thank you.

Option 2: A better converter. alas, I don't know of one.

I have a Progressive Dynamics 9180 with wizard in my rig, Just for fun I turned it off, waited till the batteries had run down a bit and turned it back on. My TS-2000 could not tell the difference, (If I let 'em run down far enough it can but that's low-batt performance v/s full-batt performance) In my rig the converter is at the back and the batteries are at the front, over 30 feet away, over 40 electrical feet, I was on 80 meters and the radio is in the middle as is the fuse panel (I had to add about 1 foot to the power leads Kenwood supplied, Very nice location, I also don't miss my net turn should I feel the need to ... UR.... Go somewhere... Since that's where I"m sitting while awaiting my turn anyway )

Yet another poster here reports he gets a lot of interference from his PD-9180 w/wizard

Same exact converter... I have no clue as to what Damon did right
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Old 01-12-2008, 01:59 PM   #5
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These converters are made as cheap as they can make them and sense they are switching power supplies they create a lot of RF noise. The reason they make so much noise is that to keep them small and light weight they take the AC in and convert it to DC than chop it with a Oscillator at around 20 to 100 KHZ now this much higher freq (compared to 60hz) can be stepped down to 13.5 volts with a very small transformer because you have a much shorter duty cycle. Now with a old fashion linear power supply you would use a huge step down transformer (60 cycles has a much longer duty cycle) step it down to maybe 18 volts run it through a regulator and filter it. Much cleaner, no RF noise but much heaver and larger. With a switching power supply you really need a lot of filtering to get a half way clean output. It needs filters on the AC input each stage and the output something that cost more to make and the manufactures just don't care about our hobby.

My now work around will be to turn off my converter with the circuit breaker and then use a old linear converter I have in the garage to charge the batteries and run everything. This converter is rated at 40 amps is rather large but all I need to do is connect it to the batteries like a charger and plug it in. A person could do the same thing with a lest say a 20 amp battery charger as long as it is linear type (Heavy) I would imagine a 10 amp would also do the trick. I used this setup when I had a tent trailer and it worked like a champ then all I will need to do it install caps on all my fans like in the heater and exhaust fans.
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Old 07-06-2009, 12:01 AM   #6
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I pulled this old thread out, originated by Andy. I still have an RFI problem in the 5er on 75/80 meters. That's the only band I'm having trouble with. Have any of you ever heard that GFI circuit breakers can cause RFI ? I was told that a few weeks back by a ham with a motorhome. I've not done any testing yet. Wondered if any of you may have heard of such ?

Thanks.



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Old 07-06-2009, 03:38 AM   #7
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Hey Jim,
Never heard of a GFI making RFI, but it might be propogating it through the AC line from another source. Try using an old portable AM/SW radio to find the source. I think you will find it is the power converter/charger. I got rid of my RFI when I sold the trailer. By the way, I had a spare converter that I put into a metal cabinet and tried to build a 55 amp 12vdc power supply. It still puts out hash, so I need to add filtering in the AC input as well as the DC output. I do have a brute force filter on the AC now which doesn't seem to help much.
Good Luck,
Andy - n1ork



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Old 07-06-2009, 08:51 AM   #8
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There are entire books on RFI. IN fact, the ARRL sells at least one at the arrl store (www.arrl.org and follow the STORE link)

This seems to be a "luck of the draw" issue. I have a PD-9180 with wizard and a Kenwood TS-2000.. I know of a few other hams who have more or less the same thing... They complain about RFI from their PD converter... Me. If I'm listening to my Kenwood, and the breaker trips.... The lights dim, that's the only way I know the breaker tripped. No change in the sound at all, ZERO interference 160 meters to 70cm that I'm able to find (in fact I go all the way to AM broadcast on the long end) ZIP.

And as I said, the others have the same converter, same batteries, same radio, same, same, same.

Check the chassis ground on both the converter's case and the radio.. All I can think of is mine is well grounded.
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Old 07-06-2009, 08:55 PM   #9
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when I initially set up the IC706 in MH, and was just powering the rig from it's own 12v battery, the noise was terrible...i replaced a few of the 12v incandesent lamps at the rigs' operating position with LED lites & noise went away...go figure, uh?
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Old 07-07-2009, 10:49 AM   #10
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Incandesent's causing noise.. That is strange.

LED's do, create RFI by the way, if not properly filtered, (those things generate noise dang near "From DC to Light" as the saying goes, in fact, the light they generate *IS* RFI., However sometimes that is what we want. True white noise generators.. Just not much of it, and thus you don't hear it in the radio.


I once made a tune up aid.. Consisted of a near-square wave generator feeding a diode... Genuine white noise with a 1,000 cycle per second on/off rate, Other than frequency you could tweak coils for maximum BEEP and your signal to noise ratio was... Also peaked.

The last step in tuning (Frequency) required other test gear.
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Old 07-07-2009, 09:48 PM   #11
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Quote:
Originally Posted by wa8yxm View Post
There are entire books on RFI. IN fact, the ARRL sells at least one at the arrl store (www.arrl.org and follow the STORE link)

This seems to be a "luck of the draw" issue. I have a PD-9180 with wizard and a Kenwood TS-2000.. I know of a few other hams who have more or less the same thing... They complain about RFI from their PD converter... Me. If I'm listening to my Kenwood, and the breaker trips.... The lights dim, that's the only way I know the breaker tripped. No change in the sound at all, ZERO interference 160 meters to 70cm that I'm able to find (in fact I go all the way to AM broadcast on the long end) ZIP.

And as I said, the others have the same converter, same batteries, same radio, same, same, same.

Check the chassis ground on both the converter's case and the radio.. All I can think of is mine is well grounded.
John, you are one of the lucky ones. I might say VERY lucky ones. Reading your post, I assume you are aware of that.

Jim



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Old 07-08-2009, 05:11 AM   #12
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This is a test. Is something broke with this thread? I see Jim posted a message yesterday, but I can't get to it. If it's in page 2, I can't get there either. Am I missing something here?



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Old 07-08-2009, 05:16 AM   #13
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That's wierd, after I posted my Test message above, I can now see Jim's post and get to page 2 of this thread. Jim, were you posting at the same time as the software update was happening yesterday? Oh well I guess it's FM. Hope you find and fix your RFI Jim.



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Old 07-08-2009, 09:17 AM   #14
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I posted that last night Andy and it looked like it should have gone to the top of page two. I would click on "Page 2" but it would consistantly take me to "Page 1". Seems to be working now.

Awhile back, when I was attempting to eliminate some things, I ran an extention cord in from an outlet outside and there was no noise. Quiet as a mouse. Here I am telling my wife, I have got to get this noise isolated and cleaned up before we leave at the end of the month. She came up with an excellant suggestion. I always feed my antenna coax in through one of the corners in the bedroom slide. She reminded me that every campground we go to has a couple of extra 120VAC outlets at the electrical pedastal. She said, "while you are running the coax in through the bedroom slide, why don't you just carry a good extention cord along and run it in by the slide as well ?" Plugging it into the extra outside 120 connection. Now why didn't I think of that ? I gave her a great big hug and said, "problem solved !" Hopefully that will eliminate any noise in the CG as it did here at home when I tested it.

I've got a good 50 ft. "heavy duty", well insulated cord I can use. I can feed it in the same time I pull the 2 RG8X lines in. I remember why I married her now.



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Old 07-08-2009, 04:29 PM   #15
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I wish I'd of thought of that b4 I sold the TT! Duh!!!!!!!!



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