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Author Topic: Computer Monitor Causing Birdies  (Read 285 times)
N1ZHE
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Posts: 68




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« on: August 22, 2004, 09:36:58 AM »

I work mostly HF digital.

I notice that 14.080 has a lot of "interference". On a lark (pardon the pun), I shut off my computer's monitor and the interference went away completely!

Changing refresh rates only moves the interference to somewhere else that I don't want it to be.

Short of buying a flat panel display, is there any way to filter the interference out? (Will a flat panel cure it?)

David, N1ZHE
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AC5E
Member

Posts: 3585




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« Reply #1 on: August 22, 2004, 09:51:51 AM »

You are probably hearing harmonics of your monitors horizontal sweep oscillator. You can try a couple of  of Radio Shack's snap on ferrites - wrap a few turns of the power cord around the ferrite and snap; ditto with the signal cable. That works fine on some monitors, not at all on others.

I have changed to all LCD monitors here in the shack. They work fine, take up less room and draw less power. And the various ones I have tried have been RF silent.

73  Pete Allen  AC5E

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KG6JEV
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Posts: 65




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« Reply #2 on: August 22, 2004, 09:53:56 AM »

How far away is your antenna from your monitor? I used to have the same problem when we lived in Northern California and my HF antenna was less than 15 feet away from the shack. We have since moved and the same antenna is now about 70 feet away and I experience no RFI from my monitor on HF - used to have bad problems with RFI into the ham radio from the monitor and from the ham radio into the computer, when we lived there. The only problem I have now is on 6m - my discone is in the attic above my shack and I have problems at 10w - also have birdies.

73,

Steven
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KC8FNJ
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Posts: 7




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« Reply #3 on: August 22, 2004, 10:24:19 AM »

David:
   I had the same noisy experience with my Dell monitor.  I called the Dell tech line with the request for help to quiet the interference on my "ham" radio.  The only suggestion they could come up with was to move the computer to another room.  (not an option)  So, the only solution I have is to turn the monitor off when the noise covers up a station I want to hear.  
    I have considered field-stripping the monitor and coating the inside with an rf shielding coating such as Electrodag, to see if it helps.  I have my doubts, however.  For the time being, I'll just hit the OFF button.
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W4TME
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Posts: 299




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« Reply #4 on: August 22, 2004, 11:17:58 AM »

I had some problems with my monitors in the shack too.  They are very close to the rig.  I tried a lot of different monitors and RFI reduction techniques.  After a lot of experimentation, I found that the following helped a lot.

1.) Reduce the computer’s video resolution.  I found that a lot of the RFI was reduced when I used a resolution that was less than the video cards max.

2.) Put several ferrites on the power cord and the cable connecting to the video card.  Place them as close to the monitor as possible. It took up to three in some cases to get rig of the RFI.

3.) Changing the sync rates don't help much.

4.) Change video card.  I replaced the old video card with a newer one and that reduced the RFI a lot.  The ones imbedded on the motherboard seemed to be real noisy.

5.) When all else fails use a Faraday cage.  The spray on shielding is a start, but I prefer to use the adhesive backed Cu foil and ground it well.

If you don't want to go to that much trouble, buy a new monitor.  Get a name brand and stay away from the cheap Pacific Rim manufactured devices.  LCDs are very quiet.

GL de W4TME
-Tim
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N6AJR
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Posts: 9908




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« Reply #5 on: August 22, 2004, 05:16:11 PM »

try an older cheep monitor, like everyone has out in the garage.. or borrow from a friend.. for some reason the older monitors seem quieter..  worth a try
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X-WB1AUW
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Posts: 559




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« Reply #6 on: August 22, 2004, 09:36:56 PM »

An easy one to try is to make sure the computer/monitor are not plugged into the same electrical outlet as your rig.
Bob
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N1ZHE
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Posts: 68




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« Reply #7 on: August 22, 2004, 10:03:35 PM »

Do you mean the exact same outlet, or the same fused electrical circuit?

David, N1ZHE
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