[TowerTalk] Computer RFI

[Bill Coleman AA4LR]

On 7/14/97 2:31 PM, Doug Westover  at westover@sneezy.sri.com wrote:

>I've got a DEC VT-220 'dumb terminal' that I use on packet that throws
>out crap all over the 20 meter band (in fact that seems to be the ONLY
>band that's a problem).

I have a WYSE 85 terminal that caused similar trouble. (Ironically, the 
85 is a VT220 clone -- perhaps in more ways than one)

>I've tried ferrites on the keyboard cable, the 
>power cord and the serial cable to the TNC, all to no avail.

I discovered that a goodly portion of the RFI from the WYSE was from the 
keyboard. By disconnecting the keyboard cable, most of the RFI went away.

>The next
>step, I guess, is trying to shield the cabinet interior. Does anyone
>have any feeling how good the shielding spray 'gunk' is? Or should I
>try to kludge something together with aluminum foil or copper sheet.

I used a can of that spray "gunk" on the inside of the WYSE. It helped. I 
also grounded the terminal to the station ground. That helped. The 
keyboard problem was cured by placing a ferrite bar in the coils of the 
keyboard cable.

Most of my RFI was in the 10m band. 

Eventually, I replaced the WYSE with a Mac. That REALLY helped.



Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@radio.org
Quote: "Not in a thousand years will man ever fly!"
            -- Wilbur Wright, 1901


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