picturedude Loc: Yosemite natl. park, Ca.

barrel shaped thing you see about 2-3 inches from the end of a cord? It's on my puter cord, also have a couple cords with the same thing at both ends and the cord loops through it and around it.

snowbear

It's a ferrite (iron) bead - it helps prevent electro-magnetic (EMF) interference in the computer cord/circuit.

DennisK Loc: Pickle City,Illinois

Thank you very much for asking this question.I have been wondering that exact same thing for many years,but was afraid to ask. :thumbup:
And thanks snowbear for providing the answer.

GPappy Loc: Finally decided to plop down, Clover, S.C.

Funny I have asked a whole bunch of electricians that same question and was always told it was a "shunt" and they had no idea as to what it was really for. I guess I know now. Thank you!

picturedude Loc: Yosemite natl. park, Ca.

Thank you very much. Now I finally know. (I just hope I can remember.)

jeep_daddy Loc: Prescott AZ

I wish they worked better than most of them do. I still get a lot of RF from my laptop charger and my plasma tv in the receive section of my ham radio station.

Bill Emmett Loc: Bow, New Hampshire

The ferrite balls are only good on the items they are on. They do not stop EMF from their equipment to your HAM radio. You need to shield your radio from the EMF in the air. Use good grounding practices, filters on you HAM radio set.

BTW, electricians will normally not know about electronic grounding. You should look into a radio/tower/electronic company for a professional who will know about this. There are electronic engineering companys who specialize in the field of EMF/RF protection.

jeep_daddy Loc: Prescott AZ

I have tried everything the 'experts' have suggested. You wouldn't believe my grounding system. It's a little harder to fix that you might think since I live in a condo and have restrictions by CC&R. I've discovered that the only thing that gets rid of the interference is to unplug my plasma tv and all laptop chargers. I think I'm going to move all my ham radio equipment out to the garage. My main electric panel is on the back of the garage and I'd only have a 5' run of 120vac power and 240vac power that can be on separate new circuits. Grounding will be next to the main panel too. This is the last straw and if it doesn't work I'll just get rid of all my non portable equipment and go totally mobile.

Bill Emmett Loc: Bow, New Hampshire

Remember, One, ground is not the same as return. Two, you must only ground in one place for all circuts on a single powersupply. Or, you will create ground loops. Make sure all your electronics boxes are grounded too, to the single ground plain. If you ever worked on your own equipment make sure you put all the RF guards back in place and connected to the ground plain. Be sure all speaker wires, and other wires are grounded in one place. And are open at one end, or they become antennas.

Bill

Bill Emmett Loc: Bow, New Hampshire

I forgot to ask, is the interfearance a humm? If so, it may be 60 hz humm, from the AC power.

jeep_daddy Loc: Prescott AZ

No, it's not a humm. On 20 meters my S meter is at S7-S8 most of the time. If I unplug my plasma tv it goes down to S5, if I unplug 2 laptop computers it drops to S3, if I turn off all power from the sub panel and run my tranceiver off a 12vdc battery I have maybe and S1 noise floor on 20M. I have a 3" wide, 1/4" thick 30" long copper ground bus behind my equipment and all equipment is grounded via 1" braided ground strap less than 20" in length to the ground bus. I had 2 ground rods about a foot apart grounding my ground bus with AWG#6 stranded copper wires but decided to remove one in case it didn't like 2 of them. My 120vac recepticles are all grounded properly - in fact, I replaced every switch and recepticle in the house with brand new.

I used to get into my surround sound speakers (on transmit) but found a loose speaker wire and a couple of open tv cables - RG6's that didn't have terminators on them. I fixed both and don't get into the tv or speakers any more.

Bill Emmett Loc: Bow, New Hampshire

This sounds like a real RF problem. I think I would find some copper screen, and make RF box trap. Put the tranceiver inside the RF screen box be sure there is no opening, ground the box and test. RF travels on the outside of the screen and will enter where it can. If the noise lessens open the tranceiver and look for ferrit donuts attached to the ground plane of the "motherboard" it only takes on loose donut to make a lot of circuit noise. A cold solder joint could even do this. Remember, when connecting grounds any ground not making good contact becomes an antenna.

jeep_daddy Loc: Prescott AZ

Thanks for the advise. I'm taking a break from ham radio now until it cools off. I might even try not grounding the shack. Some guys have told me that's what they do. I don't know.