On Fri, 13 Feb 2009 10:04:32 -0700, W0MU Mike Fatchett wrote:
>Any suggestions on where to start would be appreciated. It only seems to
>happen on 40m.
You should also call your DSL vendor and tell them that their modem has RFI
problems, and ask THEM to fix it. It IS their problem, not yours. W8JI had
issues with his modem, and got a replacement that worked.
Study http://audiosystemsgroup.com/RFI-Ham.pdf
If you want to fix it yourself:
1) Start with a choke tuned to 40M on each cable connected to the DSL
modem.
2) If that doesn't fix it, leave those chokes in place and add a choke at
the Ethernet switch or hub.
3) I've recently learned of a company in SoCal called Excelsus that sells
filters that they say will eliminate RFI to DSL modems. Google to find
them. I'm currently writing the EMC chapter for the ARRL Handbook, and
called them a week ago for a sample unit so that I could mention them in
the Hanbook. So far, no response. There's a more established company in
Ohio called KCOM who makes telephone filters that are well known to work
very well on telephone lines. It might be worth a phone call to ask if they
have a DSL filter.
73,
Jim Brown K9YC
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