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Re: Topband: Help with RFI

To: "W7KW" <w7kw.terry@gmail.com>
Subject: Re: Topband: Help with RFI
From: "Tom W8JI" <w8ji@w8ji.com>
Reply-to: Tom W8JI <w8ji@w8ji.com>
Date: Mon, 14 Jan 2013 11:25:48 -0500
List-post: <topband@contesting.com">mailto:topband@contesting.com>
I'm reposting this to the reflector:


Yes, I do have DSL. I have a very good RFI filter on the DSL line coming to the modem so I think it might be a cabling problem. Everything was working FB until recently when I reconfigured the hardware. I have a few clamshell filters and I also have some shielded cables so Monday I will do some substitutions and see if it helps. The problem is not across the entire band. It's only below 1825. Frequencies above 1825 don't bother me.

This is probably 160 meter RF triggering the modem. Common mode chokes and shield normally will not do the trick, because the problem is differential.

First, you need an immune modem. The best modem I found was a 2wire ADSL modem.

Second, filters are almost impossible to buy. Because of that, I built my own filter. I added peaking at the high end of DSL, which for ADSL ends in the upper middle AM broadcast band area.

http://www.w8ji.com/adsl_filter.htm

73 Tom

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