[TVI-RFI-EMI] Re: TVI-RFI-EMI digest, Vol 1 #32 - 2 msgs

Sun, 22 Dec 2002 10:27:31 -0500

>From what work I've done on monitors it can be really hard to eliminate the
noise. The biggest problem is that no matter what you do inside the case the
viewing screen is a BIG opening which allows the RF to get out.

Try the following.

Do you get the noise by just turning the monitor alone with the video cable
disconnected on?
Most likely not.

With the PC up and running does the noise go away when you disconnect the
video line from the PC?
Most likely yes.

If the above are true it's most likely a mid to late 80's vintage VGA
monitor with all of the video drivers mounted on the neck of the CRT.

Try adding a few type 43 ferrites (the kind you find at flea markets and
Radio Shack) to the cables attached to the board mounted at the neck of the
CRT.  You might also try to add a ground plane to that board.

These drivers use to be a major pain in the butt to pass the FCC Class B
compliance limits. The FCC use to make the Test Houses put scrolling "H" s
to drive the video amps as hard as they will go.

Good luck

Dennis Hennigan WA1HOG
ARRL NH TC
FN42as
Big Towers  Small Antennas
6,2,220,440,902,1296,
2304 and 10GHz

----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Sunday, December 22, 2002 4:01 AM
Subject: TVI-RFI-EMI digest, Vol 1 #32 - 2 msgs

> Send TVI-RFI-EMI mailing list submissions to
> [email protected]
>
> To subscribe or unsubscribe via the World Wide Web, visit
> http://mailman.qth.net/mailman/listinfo/tvi-rfi-emi
> or, via email, send a message with subject or body 'help' to
> [email protected]
>
> You can reach the person managing the list at
> [email protected]
>
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of TVI-RFI-EMI digest..."
>
>
> Today's Topics:
>
>    1. Very noisy computer monitor (Gert E. Janssens)
>    2. Re: Very noisy computer monitor (David Moisan)
>
> --__--__--
>
> Message: 1
> From: "Gert E. Janssens" <[email protected]>
> To: <[email protected]>
> Date: Sat, 21 Dec 2002 20:17:30 -0600
> Subject: [TVI-RFI-EMI] Very noisy computer monitor
>
> (it seems like my first message never made it, so I'm resending it)
>
> Hello all,
>
> I have a 15" monitor that produces a lot of noise, from HF to VHF (and =
> possibly higher - can't test).
>
> Since it was a gift, I'm not willing to dump it and just get a new one, =
> but rather have the problem fixed, or at least significantly reduced.
>
> What I tried so far: loads of chokes, wrapping it in about a pound of =
> aluminum foil and went as far as totally spraying the inside with =
> EMI/RFI shield coating. All grounds appear to be good, and I added some =
> to the monitor by itself.
>
> So far no luck. The problem remains, doesn't even go away a little bit.
>
> The noise is quite strong, up to S7 on 10 meters (and more on 15) and =
> appears about every 40 kHz. One day I thought I solved it by changing =
> the screen's refresh rate; but after I moved to a different frequency I =
> found out that it just moves the interference...
>
> So I'm looking for some advice. Anything that might help is welcome!
>
> Thanks in advance, happy holidays, 73,
>
> Gert - K5WW
>
>
> --- StripMime Report -- processed MIME parts ---
> multipart/alternative
>   text/plain (text body -- kept)
>   text/html
> The reason this message is shown is because the post was in HTML
> or had an attachment. Attachments are not allowed.
> Please post in Plain-Text only.---
>
> --__--__--
>
> Message: 2
> Date: Sat, 21 Dec 2002 23:46:38 -0500
> To: <[email protected]>
> From: David Moisan <[email protected]>
> Subject: Re: [TVI-RFI-EMI] Very noisy computer monitor
>
> A 08:17 PM 12/21/2002 -0600, Gert E. Janssens wrote:
> >So far no luck. The problem remains, doesn't even go away a little bit.
> >
> >The noise is quite strong, up to S7 on 10 meters (and more on 15) and
> >appears about every 40 kHz. One day I thought I solved it by changing the
> >screen's refresh rate; but after I moved to a different frequency I found
> >out that it just moves the interference...
>
> If you have done all possible measures to your monitor (which seems to be
> the case), than there is something besides your monitor that may be
> reradiating.
>
>
> What and where is your antenna set up?  inside, outside,???
>
> What computer do you have (processor, speed, other peripherals)?
>
> Is your computer connected to the radio via RS-232 (control) or audio
> (speaker and mic)?   This is important.
>
> Take care,
>
> DAve
>
> David Moisan, N1KGH   ARES/SKYWARN                [email protected]
> Invisible Disability:
http://www1.shore.net/~dmoisan/invisible_disability.html
> ATS-909 FAQ:  http://www1.shore.net/~dmoisan/faqs/sangean/ats909faq.html
>
>
>
> --__--__--
>
> _______________________________________________
> TVI-RFI-EMI mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/tvi-rfi-emi
>
>
> End of TVI-RFI-EMI Digest
>