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

On Feb 25, 1:58�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

I get them from Mouser. They are 1-2 bucks apiece.

Gary N4AST

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

http://www.palomar-engineers.com/

http://www.palomar-engineers.com/

Thanks, they even have an RFI kit for reasonable.

On Feb 26, 2:36�pm, "R.Scott" wrote:
http://www.palomar-engineers.com/

Thanks, they even have an RFI kit for reasonable.

Yep, Palomar, and the Wireman are good sources. They get the snap on
cores and re-package them, and this costs a little extra. If you get
them from a parts house such as Mouser or Newark, you will save a
little. Shipping costs will be a little less as well. Looking at my
latest Mouser catalog they have 3 pages of EMI cores.

Gary N4AST

wrote:
On Feb 26, 2:36�pm, "R.Scott" wrote:
http://www.palomar-engineers.com/
Thanks, they even have an RFI kit for reasonable.

Yep, Palomar, and the Wireman are good sources. They get the snap on
cores and re-package them, and this costs a little extra. If you get
them from a parts house such as Mouser or Newark, you will save a
little. Shipping costs will be a little less as well. Looking at my
latest Mouser catalog they have 3 pages of EMI cores.

Gary N4AST

I like to do business with fellow radio types, even if it costs a few
pennies more.

On Feb 26, 5:58�pm, dave wrote:
wrote:
On Feb 26, 2:36 pm, "R.Scott" wrote:
http://www.palomar-engineers.com/
Thanks, they even have an RFI kit for reasonable.

Yep, Palomar, and the Wireman are good sources. �They get the snap on
cores and re-package them, and this costs a little extra. �If you get
them from a parts house such as Mouser or Newark, you will save a
little. �Shipping costs will be a little less as well. �Looking at my
latest Mouser catalog they have 3 pages of EMI cores.

Gary N4AST

I like to do business with fellow radio types, even if it costs a few
pennies more.

So do I, but Scotty indicated he wanted REASONABLE (his words). I
have just bought a number of them for a non ham application, and
depending on how many you need, the savings can be significant.

Gary N4AST

wrote in message
...


I like to do business with fellow radio types, even if it costs a few
pennies more.

So do I, but Scotty indicated he wanted REASONABLE (his words). I
have just bought a number of them for a non ham application, and
depending on how many you need, the savings can be significant.


The absolute cheapest place to get ferrites has been the swap meets. In
Southern California, we have two that I know: Santee in San Diego and TRW
in Los Angeles. Tons of stuff -- old and new.

The problem is that the vendors often have donuts that are advertised as EMI
suppression ferrites, but they can't identify the mix. The mix determines
the frequency range, so if you try a Mix 43 donut at VHF, you may not see
the desired improvement.

I have a kit of ferrites that I bought for dirt cheap. Why so cheap?
Unlabeled, that's why. I take a shot with one donut and it does nothing, I
try another. For four bucks, I can tolerate some of this annoyance.

I just did a fix with one donut for RF getting into my computer keyboard on
PSK31. A few turns of the keyboard cord through a donut and the problem
went away. Luck and science married.

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.

"Sal"

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?

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