[RTTY] Keyboard RFI problem solved

[Bill Turner]

At 08:45 PM 8/17/2005, Don Hill AA5AU wrote:
>Interesting information Bill.
>
>I would have thought a USB keyboard would have been worse with RFI as that has
>been my experience here with other USB devices (but not keyboards).  The best
>solution I've had for keyboard RFI is to wrap the keyboard cable around a
>ferrite rod.  This was a trick I learned from Eddie, G0AZT, down in the 
>Bahamas
>many years ago.

The ferrite rod sounds like a good idea, especially if you use one designed 
for an AM radio loopstick antenna, which should be the right material.


>Were you using ferrite beads, toroids or rods?  I'm thinking the reason the
>ferrite didn't help is because perhaps they are not of the material to 
>attenuate
>frequencies that low.  If they are made of material 43, which I think is 
>common,
>then they won't attenuate 160 meter frequencies.

I used eight of the clamshell type snap-on ferrites and one of the double 
"U" type with three turns through it. I have no idea which material. They 
were some I've had laying around for years.

The reason I suspect it wasn't actually the keyboard itself is that as I 
raised and lowered the power output the freezing occurred at the same 
point, regardless of which keyboard or whether the cable had any ferrites 
at all on it. I would think even the "wrong" ferrite material would have 
made a slight difference, but it didn't. That made me suspect the problem 
was occurring inside the computer itself. This is all speculation, of course.


>Here's a great chart showing material and what frequencies they attenuate:
>
>http://www.cwsbytemark.com/CatalogSheets/PDF_Files/2_12.pdf

Good chart. I'll save a copy. Thanks, Don.

Bill, W6WRT