RFI from Big Screen TV.... Grrrrrr! Help???

[W4LTM]

Hi gang,

I posted this elsewhere a number of months back and did not get any answers I could live with, so I am posting it here where a wealth of knowledge has always been shared.

I have a 60" Phillips / Magnavox TV (rear projection) that is Downstairs on the other side of the house (back of house) from my upstairs shack.  The shack and downstairs are on separate circuits.  My Multiple Inverted V's are in the backyard.  The TV is pointing towards the front of the house and at a small angle from the shack.

Now, when the TV is turned on the RFI noise from the TV is so loud it makes all of 80 and small bits of other bands useless.  My kids like there TV and I like AM, but with noise like this I can't do a thing.  I have put on snap-on, wire through, loop around, and all other kinds of Cores to stop the RFI from getting out, but I am afraid it may be radiating from the CRT 's in the TV or some other part that is not cable related.

Any ideas?  Any at all?  I am at a loss.

Thanks,
Matt

[Jim, W5JO]

Good luck Matt.  There is an 800 number to call in the user's manual.  You can try, but don't expect much from them but a hang up.  Your best bet is document and report it to the FCC and copy the CEO with your letter.  Part 15.

[Jack-KA3ZLR-]

Tuff Nut to crack here Matt, Um, well, you could try a Tuned Loop to ground and Capacitively try drawing the rf to ground...although finding the Reference Freq to tune the loop to is your first priority...all this being done internally...Check the chassis Ground Potential...Um, check Circuit schematic Grounds and go over them real well, this thing shouldn't be emitting this much RF...at least in my mind something is amiss...although I've never had a big screen so...maybe the Boys can come up with something here...

What say fellas a brother is having a Problem here...

[Vinnie/N2TAI]

I had a similar problen with a Daewoo DVD player tossing hash on 80. It did not even have to be on just plugged in. I think the noise came from the switch mode power supply. solved the problem by giving the DVD away. Interesting the manual said it met FCC regs but the DVD can create interference and in the case of radio interference to try moving the radio to a different circuit. I thought that these things were not to produce any interference. Go Figure

[ka0pad]

Try one of the noise cancelling box'es if nothing else works, like the mfj1026 maybe?

Good luck with it.

Larry

[N9NEO]

Yes noise probs can be tuff nuts to crack.

I don't have much to add.   I suppose rfi is being transmitted from tv set and picked up by antenna.  I wonder if noise is being transmitted through air like you said, or maybe into your 115v line, or maybe out the antenna jack and down your antenna coax.  That is, the noise is ending up on cables which are re-radiating into the ether.

I would think all would be likely candidates.  

Maybe you need to get a little more aggressive with the filter.  Try a good emi filter designed for smps type applications very close to back of tv on 115v line.  Making sure you have good AC grounds  near tv might help emi filter work.


  Does the noise get better if tv antenna cable disconnected?  Maybe a few turns of the antenna coax wound on a hi-perm core near back of set might help.  

If EMI is being transmitted directly and not conducted thru lines then maybe some kind of sheilding between tv and your antennas might help.  The noise does go away when you disconnect your 80m antenna, yes?  I guess this might be too radical an approach for some.  Ferrite tiles glued to living room walls might not be so pleasing to the female eye.  Maybe copper or steel or aluminum plate strategically placed at side of tv and grounded might be all the magic you need.

Please let us know how problem is resolved.

good luck
Bob

[K6JEK]

Do all that stuff.  If you're still hosed,  you might consider the set up I use here in the Noisevale (Silicon Valley).  I use a tuned loop for receive.  It has a very sharp null.  I point the null at the nasty noise of the day. I also use an MFJ 1025 noise cancelling phasing gizmo with the transmit antenna and the loop.

The loop is the one in the ARRL antenna book, a shielded (coax) loop.  It's dead simple to build and effective.

Jon

[W1DAN]

Hi:

I have some RFI from my PC.

After e-mailing the ARRL and receiving some correspondence (both helpful and not. They suggested a totally linear external DC supply) I opened my PC's power supply. There was none of the usual RF hash filter at the AC line input. So I added one right at the input (like bob suggests above). This brioght my noise from S9+30 to S6, and I am living with that.

I suggested an article to the ARRL where they would either test some RF quiet PC power supplies or create a new recent article on how to sniff and filter your noise. They declined.

My real problem is the receiver I am using has a wire antenna in the same room as the computer. I need to get my antenna away from the PC.

So I would suggest:

Take a well shielded receiver. Make a small loop antenna with a long enough piece of coax atatched and sniff around the TV. The noise may be radiating from the power line, or other lines going to the TV. Or it may just be radiating from the TV case. You would then find where to better shield or filter.

Unfortunately the best solutions may be to either separate the ham antenna from the house (what I should do in my case) or enclose the TV in some wire screening and better filtering on the lines coming to the set(yuk!).

I am finding that even though items have the UL rating does not mean they pass RF noise emissions limits.

Hope this helps some. Good luck!

73
Dan
W1DAN

[Mike/W8BAC]

I remembered seeing something similar on the CCA reflector some time back. Here it is. Good luck.

Mike


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Subject:  {collins} TVI FIXED!!!!!
From:  John May <johnmay@bellsouth.net>
Date:  Sun, 09 Sep 2001 08:25:23 -0400
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WOW ... Jerry K7ENP pegged it!!

By simply plugging the TV into the outlet instead of going through a
surge protection outlet strip the problem went away.  This hash was
between 20-40db over s9.  It was wiping out almost everything - AND NOW
IT"S GONE!

The outlet strip is rate for about 600 watts and I was pulling about
300.  Should have been OK.  Jerry's suggestion was that lighting might
have hit it and I not know it, is probably correct.

I would like to thank Jerry and everyone who helped.  I learned quite a
bit from the information I received.  This was a difficult situation for
me.  I had just bought the family this new TV, but if I wanted to use
the rig at the same time (which seemed like most of the time) it was
impossible.  This is truly a great list!

Thanks again Jerry - DX  here I come!  John K6MAY.

I have repeated Jerry's email below...

Hi John have you tried Exchanging or replacing the
Dish with components? I had s8 on my kwm2/a when i
turned tv off it dropped to s3 When I threw out the
surge protector, and plugged the tv in to the wall
my s meter dropped to nearly 0 Hi Moral here my
surge protector was hit with lightning and I didn't
know it. 73 your friendly ham Jerry k7enp





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[W4LTM]

Thanks for all the help gang.

Lots of good ideas and I will look into them.  It will be nice to get this darn thing fixed.

Thanks again,

Matt

[Glenn K2KL]

It may seem like the easy way out, but the JPS ANC-4 is a God sent!
I've been a very happy customer for several years now. At my QTH, there are just too many problem noise sources. Not just from my house, but all the surounding homes as well. Add to that all the crud coming from the strip-mall down the street, neon signs, pulse type battery chargers, computer monitors, electric doggie fences, etc, etc, etc...... there's no way I could track down and quiet all this garbage.  :evil:  :evil:

Experimenting with different noise antennas is the key to getting the most of of the device. I don't know about the MFJ device but the ANC-4 is truly incredible. At my last QTH, the ANC-4 worked so well at removing the noise, I was able to copy weak AM broadcast stations from Europe that were otherwise unreadable. Needless to say, I'm looking forward to next year's move to 10 or more acres in North Carolina.    

Here's a link to a PDF on the ANC-4. It's now being manufactured by Timewave who bought the design from JPS.

http:// http://www.timewave.com/Acrobat/ANC-4DS.pdf

Thanks for all the help gang.

Lots of good ideas and I will look into them.  It will be nice to get this darn thing fixed.

Thanks again,

Matt

[W4LTM]

I have a MFJ-1026 deluxe Noise Canceler enhancer.  I just acquired this unit so I have not had time to work with it and figure the best noise antenna.

My ANC-4 had the relay hang and I fried a few resistors (R31, 32, & 33 I think it was).   I replaced the resistors, but the darn thing just never worked after that.

How does the 1026 compare with the Anc-4?

I have not had a chance to do further testing on the TV as work has had me on an overload schedule.

Cheers,
Matt

[Rob K2CU]

Many switchers have varistors in the AC input line for some sort of surge protection.  When you open up the set to inspect for input line filter, check this as well, even replace with a new one.  Also consider adding snubbers. a simple .001 uF !KV ceramic cap in series with a 27 to 50 ohm resistor. add to any supply volatge line that you suspect. it is not enough to just add bypass caps as they are probably already there. you need the resistor to absorb th eenergy.
IF all else fails:

This may seem a bit drastic, but it has worked before. Install a high performance line EMI filter.  Then purchase a hgih conductivity copper spray paint (many sources on the web) and spray the interior of the cabinet per directions for EMI shielding.  Finally, purchase a conductive transparent EMI film for front of TV. You will need copper foil tape with conductive adhesive to connect the shielding sedctions together.  You may need to add copper braid(s)  to connect case to input coax ground.  Also, as suggested above, add a choke balun to the input coax right where it enters cabinet, as well as a coax high pass filter, and ground case to sprayed on cabinet coating.  Be sure all filter cases and gounds are connected with braid and or copper foil.

[Glenn K2KL]

You probably fried one of the FET's Matt. That should be an easy fix.
I mostly use separate xmtrs and rcvrs so the relay thing isn't an issue for me...

Sorry, I've never played with the MFJ unit. Had no reason to since the ANC-4 worked so well.

I have a MFJ-1026 deluxe Noise Canceler enhancer.  I just acquired this unit so I have not had time to work with it and figure the best noise antenna.

My ANC-4 had the relay hang and I fried a few resistors (R31, 32, & 33 I think it was).   I replaced the resistors, but the darn thing just never worked after that.

How does the 1026 compare with the Anc-4?

I have not had a chance to do further testing on the TV as work has had me on an overload schedule.

Cheers,
Matt