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#1
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Whats a Good Source for Ferrite Donuts
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 |
#2
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Whats a Good Source for Ferrite Donuts
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" |
#3
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Whats a Good Source for Ferrite Donuts
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? |
#4
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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. |
#5
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Whats a Good Source for Ferrite Donuts
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 |
#6
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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. |
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