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RFI on computer

Apr 29th 2012, 18:59

NM0L

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
I just got a Tentec 4020 QRP 5 watt rig. It is causing interference on my wife's Mac computer! 5 watts!! ?? Where do I place a ferrite?
Apr 30th 2012, 00:52

W0BTU

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
It's impossible to say where the RF is entering the Mac. You need to do a little experimenting, and the first place I would start is the power cord.

I have seen RF enter the computer through the AC line, keyboard cable, network/modem cable, mouse cord, and speaker cables. Solving this problem may involve ferrites on more than one cable, and which cable(s) is something that nobody can tell you for certain.

Or it may involve reducing common-mode currents on your antenna feedline. Can you describe your antenna and feed system? An end-fed antenna with no radials would be the most prone to causing RFI, and at 5 watts, that's what I'm guessing you have there.

And how close is your antenna to her computer?

Another thing is the type of ferrite needed. It would help if we knew what bands you operate when you have this problem. A good read is http://audiosystemsgroup.com/RFI-Ham.pdf

73, Mike
www.w0btu.com
Apr 30th 2012, 18:01

AA6E

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Be a little more explicit. What kind of interference? Is it something you hear, something you see on the screen? Or does it kill the machine? :)

In my experience, the most frequent problem is RF getting picked up in the audio leads to external (amplified) speakers. Ferrites on those wires usually do the trick. Keep coax and antenna wires separate from the computer as much as possible, etc.

73 Martin AA6E
May 3rd 2012, 06:12

W0BTU

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
This thread is a poster child of why I'm about ready to quit the forums.

Somebody asks a question, people with some technical knowledge about the question try and help them out, but there's not the least acknowledgement or thanks by the OP.

Hasta la bye-bye.
May 3rd 2012, 19:12

AA6E

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Forum admins please note: It would be very helpful to have a "subscribe thread" default option that would send an email whenever a new message comes in on a thread you started or contributed to.

73 Martin AA6E
May 4th 2012, 00:59

W0BTU

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
GREAT suggestion, Martin! Every major ham radio forum but this one has this feature.

However, I suggested this and other badly needed changes to this forum at http://www.arrl.org/forum/topics/view/48 (on July 28, 2011) as well as other places. But nothing has happened to date. It does not make the ARRL look good, to put it mildly.

BTW, perhaps I was a little harsh in my post above. Perhaps the OP had an emergency. Anyway, a subscription would sure help solve this issue.

73, Mike
www.w0btu.com

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