<html>
<head>
<style><!--
.hmmessage P
{
margin:0px;
padding:0px
}
body.hmmessage
{
font-size: 12pt;
font-family:Calibri
}
--></style></head>
<body class='hmmessage'><div dir='ltr'>Perhaps a:<br><br><h2 class="productTitle"><a href="http://www.radioshack.com/product/index.jsp?productId=2103222">RadioShack® Snap-Together Ferrite Choke Core (273-105)<br></a></h2>might do the trick, or maybe a:<br><br><h2 class="productTitle"><a href="http://www.radioshack.com/product/index.jsp?productId=3012599">Snap Choke Core (273-069)</a></h2><br><br>or something similar.<br><br>Jim WB6NIL<br><br><div>> From: Benjamin@kb9lfz.com<br>> To: app_rpt-users@ohnosec.org; Repeater-Builder@yahoogroups.com; radiomodifications@yahoogroups.com<br>> Date: Sat, 15 Jun 2013 23:58:39 -0400<br>> Subject: [App_rpt-users] EMI/RFI issue<br>> <br>> Greetings All,<br>> <br>> While thinking of a way I can turn my node into a portable allstar node,<br>> it has been discovered the computer I'm using, generates RFI/EMI over<br>> the DC power connection.<br>> <br>> The setup is as follows presently, which has zero *known* EMI/RFI<br>> issues. The radio is powered with an older linear 3A regulated power<br>> supply, which a parallel connection to a 12V 18Ah battery. All leads are<br>> kept short, under two feet. The radio is kept on 5W.<br>> <br>> The computer has a 12Vdc connection, and it's presently using an ac/dc<br>> SMPS, one that can be bought on eBay for about $10. <br>> <br>> Both of these are plugged into the same outlet strip, and as stated,<br>> zero discovered EMI/RFI issues.<br>> <br>> The radio audio connections to the computer have the center conductors<br>> isolated with a 10nF cap. <br>> <br>> Just as soon as I decide to power the computer from the battery, the<br>> radio has noise across every tunable frequency. Even if I disconnect the<br>> radio completely from the node, there is noise on the radio. From what<br>> is apparent to me, the noise is coming from the computers internal power<br>> supply section, riding the power wires back to the battery, and then to<br>> the radio.<br>> <br>> I see there are plenty of EMI/RFI filters I can purchase. However, I'd<br>> like to maintain the Amateur Radio Spirit of creation for this case, so<br>> I'd like some pointers on what I should test for, and construct some<br>> EMI/RFI filters.<br>> <br>> I have seen there are common mode and differential mode chokes filters,<br>> and some filters have both kinds of chokes. I'm not really sure the<br>> difference, besides the way the components are installed in the circuit.<br>> <br>> If you find it better to talk in person, contact me via allstar or look<br>> for my phone number on the internet.<br>> <br>> ~Benjamin, KB9LFZ<br>> Allstar node 28569<br>> <br>> _______________________________________________<br>> App_rpt-users mailing list<br>> App_rpt-users@ohnosec.org<br>> http://ohnosec.org/cgi-bin/mailman/listinfo/app_rpt-users<br></div> </div></body>
</html>