Unfortunately, the K-Com and Z-Block filters will also block or severely
attenuate the DSL signal, which occupies roughly the same band as AM
broadcast stations. Many's the installation where I had to remove a
Broadcast band RFI filter in order to get a DSL signal to pass. On a few
occasions it's come down to the customer having to put individual RFI
filters on each phone, rather than a single filter at the telco network
interface, to allow a clean DSL signal through from the interface, and also
not have to listen to Elvis on KOMA in all the phones. A pain, but it
worked. I wish I could offer an easy solution, but Efficient (and Westell,
Alcatel and others) don't build their modems with any significant
RFI-proofing in mind.
If you insist on having the modem near the computer/radio shack, you might
try coating the inside of the modem shell with the peel-and-stick aluminum
tape used by air conditioning installers. Just take care to preserve the air
venting, these things can run pretty hot.
Another other possible (and likely better) solution is to remotely locate
the modem. There's no rule that says the modem has to be anywhere near the
computer or the ham shack. After all, it only requires the telephone line
DSL signal, power, and an Ethernet cable. The only connection between the
modem and the computer is a short Ethernet cable, and it doesn't HAVE to be
short. Ethernet will work fine using a pretty long run. Make up a looooonnng
Cat 5 cable, locate the modem as far as possible from the shack, and run the
Cat 5 between the modem and the NIC on the computer. Shielded Cat 5 wouldn't
hurt, although I really don't think it's necessary. I'd still use lots of
ferrite to boot . Let us all know how this works if you try it, don't hear
of this problem very often, kind of peculiar to hams.
Hope this helps.
73, Jerry W5KP (Your Friendly Ma Bell DSL tech, who does DSL 8-10 hours a
day for other people, but lives far out in the woods with his miserable 40K
----- Original Message -----
From: "Jon Ogden" <firstname.lastname@example.org>
To: "Richard Zalewski" <email@example.com>; "Towertalk"
Sent: Thursday, September 05, 2002 9:02 PM
Subject: Re: [Towertalk] RF and Speed Stream
> on 9/5/02 6:43 PM, Richard Zalewski at firstname.lastname@example.org wrote:
> > Any one out there using a Speed Stream 5667 DSL Modem or similar
> > modem by Efficient Networks? Having a bear of a time keeping 40 & 20 M
> > out even at low power.
> > I loose sync with 7Mhz or 14Mhz RF in the environment. I have lots of
> > right kind of ferrite on the 3 external connections to the modem/router
> > can't seem to solve the problem.
> I have a Speedstrean 5260 DSL modem. I don't have so much of a problem on
> 20M, but do have problems on 40 and 80 m. I don't have the problem at low
> power but only high power.
> One thing both of us might want to try are phone line filters like form
> K-Com. The problem is, I don't know what their frequency response is.
> This is a good question for the experts on the RFI reflector.
> Jon Ogden
> NA9D (ex: KE9NA)
> Life Member: ARRL, NRA
> Member: AMSAT, DXCC
> "A life lived in fear is a life half lived."
> Self Supporting Towers, Wireless Weather Stations, see web site:
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additional 5 percent off
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