Whats a Good Source for Ferrite Donuts
 

"dave" wrote in message
m...
Sal M. Onella wrote:

I just did a fix with one donut for RF getting into my computer keyboard
on
PSK31.

How much power do you use for psk31?

I generally set it for about 50 watts to get a decent fade margin. With
good propagation, I've used as little as 15 watts and had a solid QSO. (I
retweak it for each QSO, since the equalization of the audio input isn't
flat. 1500 Hz audio might give me 50 watts, but if I click at 800 Hz, I
might get 15 W. The rig has an equalizer in it. Ya think maybe I should
learn to use it?)

I put a newer computer in service for PSK and I found that at 50 watts I was
getting doubles and triples of many of my keystrokes during QSOs. When I
dialed the power down to 25 watts, the problem went away. Ferrite time.

Funny, with the old computer (a 486 running Win95) the RF got into the mouse
only. With the new XP computer, the RF got into the keyboard only. Go
figure.

Whats a Good Source for Ferrite Donuts
 

"Roy Lewallen" wrote in message
...
Sal M. Onella wrote:
. . .
Could I set up a test jig to figure out the mixes and frequencies? Yes,
maybe. Give me some ideas for the test circuit. I have a 1GHz spec-an
&
tracking generator.

To determine if a core is useful, you need some way to measure the
impedance. And unless you're using the cores for high power or high Q
applications, all you really need to know is the magnitude of the
impedance. An "antenna analyzer" is a really simple and portable way to
check flea market beads if you have one -- just put a short loop of wire
between the terminals and run it through the bead's hole. If you're
measuring at low frequency where the impedance might be low, you can use
more than one turn and calculate the one-turn (one pass through the
hole) impedance as the measured value divided by the square of the
number of turns.

If you really need to know the mix, you'll probably need to be able to
measure the R and X components of the impedance as well as the core
dimensions, then refer to catalogs of various vendors to find a match.

Roy Lewallen, W7EL

Thanks. That sounds easy enough. I have the analyzer.

Whats a Good Source for Ferrite Donuts
 

On Feb 25, 2:58*pm, "R.Scott" wrote:
Want to see if I can remove some of the RFI getting into the puter
(and maybe back into the rig).

So I want to wind some of the Keyboard/Mouse/Video cords in some
Donuts. *Anyone know where I can grab em easy and REASONABLE :)

Scotty W7PSK

Most any good bakery can make up special orders. They will probably
have a minimum order. When my wife request lemon-rasberry she had to
order twelve dozen.

Jimmie