[RFI] DSL/Router Problems

[W2RU - Bud Hippisley]

On Aug 16, 2010, at 4:29 PM, Bill Gillenwater wrote:

> I've been having this problem since I moved to the new QTH.  I use DSL and a wireless router.  The router is located in a separate part of the house. Everything works fine until on 80 meters. Low power is no problem. Anything over 100 watts and my telnet/internet connecting is lost.  I can run a KW on the other bands with no problem. I have put RF cores on all of the wires leading to the DSL  box and the router, still no success. I suspect that the phone wiring that runs through the walls and in the attic, may be the culprit, not sure. But just on 80 meters does this problem surface.  Any ideas out there????

Having been through the debug of this exact issue over the past three years, I am almost certain your problem is front-end overload of the DSL modem by RF in the 1 - 4 MHz region.  DSL has its primary frequency components in the 1.5 to 2.5 MHz range, and the internal circuitry is extremely susceptible to 160-meter and 80-meter RF, the former more so than the latter.


*My* first question would be:

1.  Do you operate 160 meters?  If so, what happens on *that* band?

My second question would be:

2.  What route does your incoming telephone line follow before it gets to the DSL modem?  Specifically, how close does it get to your 80-meter antenna and what is its orientation relative to that antenna?

My third question would be:

3.  How long is the telephone line between your house and the telco electronic switch where the card that drives your specific telephone line is located?  (You may need to ask the telco tech that question.)


Here are my first two "extreme" recommendations:

A.  Replace the DSL internet with cable internet.  (But you probably don't have that option where you live.)
B.  Move -- either closer to the telco DSL switch or into an area where you can get CATV internet.

Now, some less drastic measures:

C.  Relocate and/or reorient your 160-meter and 80-meter transmitting antennas to reduce coupling between them and the outdoor telephone wiring carrying the DSL signal to your house.
C-1.  Alternatively, relocate your telco entrance wire to get it farther from your transmitting antennas.
D.  Locate the DSL modem (and the wireless router, if necessary) on the inside wall right where your telco service enters and your telco ground is located.
E.  Make sure you're using a "whole house" telco-supplied DSL filter at the telco service entrance, so that you don't have DSL signals running throughout your house on the wiring going to your wall jacks.
F.  Use one or two 2.4-inch Type 31 ferrite donuts right at the input to your DSL modem, and wrap as many turns of the telco wire through it (them) as you can, up to perhaps a dozen or so.  Ask the telco tech for additional telco wire with tightly twisted pairs, if necessary.
G.  Ask your telco tech if he can get you one of their "commercial" DSL modems.  This is typically in a metal box, tends to be more "bullet-proof", and may be somewhat older DSL technology, hence may not get you the same peak speeds you get with your current box (when you're not operating 80 meters, that is).
H.  Add Type 31 ferrites to *all* leads going into and out of your DSL modem, including the DC power lead and the ethernet cable between the modem and the wireless router.  The ferrites must have as many turns of those leads on them as you can manage, and they must be located right at the DSL modem.  (If I showed you a picture of my DSL modem in my garage, you would laugh out loud.)

I can defend *all* of these recommendations (including A & B) with details of what went on here over the past three years, but I'm trying to give you the most likely *solutions*, not a novel.

You might also ask the tech to try shielded wire between the DSL modem (on the inside) and the NIB (Network Interface Box) & ground rod on the outside, but in my case that didn't do much for us -- probably because that distance is only about 4 or 5 feet in my current installation.

Good luck!

Bud, W2RU