[RTTY] Keyboard RFI problem solved

[Don Hill AA5AU]

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.

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.

Here's a great chart showing material and what frequencies they attenuate:

http://www.cwsbytemark.com/CatalogSheets/PDF_Files/2_12.pdf

73, Don AA5AU



-----Original Message-----
From: rtty-bounces at contesting.com [mailto:rtty-bounces at contesting.com] On Behalf
Of Bill Turner
Sent: Wednesday, August 17, 2005 10:15 PM
To: rtty at contesting.com; cq-contest at contesting.com
Subject: [RTTY] Keyboard RFI problem solved

I've been playing around on 160 meter RTTY the last few days and had a problem
with the keyboard freezing when the power exceeded a certain level, around 1kw
output. I tried three different keyboards and enough ferrites on the keyboard
cable to anchor a battleship but no luck. In fact, no improvement at all. And
that got me to thinking: Why didn't the ferrites help?

Perhaps the problem isn't in the keyboard at all, but rather the connection
inside the computer, since all three keyboards had exactly the same sensitivity
to the power level, and adding ferrites made no change in the sensitivity.

Long story short: I happened to have a USB keyboard laying around, so I tried
it. Presto! Problem solved, perfect operation at any power level. I can't say
this would work in every instance, but it's worth a try. The keyboard is just an
inexpensive one made by AOpen.

One problem with this is the BIOS does not recognize a USB keyboard, so it must
be set to not stop on keyboard errors, and if you want to hit DEL to set the
BIOS, you have to temporarily plug in a regular keyboard.

Something to keep in mind if you have keyboard RFI problems.

Bill, W6WRT

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