I have had DSL service from Frontier Communications here in the remote
wilds of upstate NY for about five years. Prior to this summer I had
arrived at a tolerable "truce" between my legal limit 160-meter
transmissions and my DSL link -- a truce which depended primarily on
the use of Type 31 ferrites on all the cables coming into the telco-
supplied Siemens Speedstream DSL modem: power from the wall-wart, the
phone line, and a few ethernet cables.
During that period, my DSL modem was located in the basement of the
_older_ part of our house, about 100 feet from my transmitting
vertical, which is about 30 feet from the _new_ end of the house,
where my shack is. At the time, the telco entrance and network
interface device (NID) were at the old end of the house, just beyond
my radial field, but my AC service entrance was (and still is) on a
"new" exterior wall, a few feet from my shack, so I could have a
single point ground (SPG) for everything coming into the house (except
the phone line).
To minimize future lightning damage to home electronics equipment that
necessarily bridges the AC power and the telephone line (cordless
telephone base, fax machine, satellite TV receiver, etc. PC fax/
modem), this summer I had the telco folks relocate their entrance
point so as to put their NID right next to the AC utility meter, so
they could attach to the same SPG. This, of course, means that the
buried phone line (shielded twisted pairs) is now about 125 feet
longer that it was. More importantly, it now comes within about 35
feet of my transmitting vertical, and lays within part of the radial
field for that antenna.
The telco guy installed a plastic-enclosure whole-house DSL filter
immediately adjacent to the NID, and then ran (perhaps 20 feet of)
unshielded Cat 5E TP up to the room above, where the DSL modem is now
located (next to my shack).
Now no amount of filtering with Type 31 ferrites keeps me from
shutting down the DSL modem on either 160 or 80. Since my wife works
from home much of the time, and internet connectivity is an important
part of her job, this is an intolerable situation for her.
Over the past two weeks the local telco tech and I have been trying
various things to get my DSL interference rejection back to its
previous "acceptable" level. Things that have not worked include:
* Temporarily disconnecting all "optional" cables (ethernet links)
from the modem
* Replacing the unshielded Cat 5E TP from the DSL filter to the
modem with shielded TP, grounded only at the SPG end
* Moving the DSL modem to the old end of the house by extending
the DSL wiring (using unshielded Cat5E; we didn't have enough shielded
TP on hand)
* Filtering the POTS wiring in the house where it comes out of the
DSL filter box
* Removing the POTS wiring from the DSL filter box entirely
* Disconnecting the lightning arrestors in the NID
* Skipping the NID and the DSL filter box completely (i.e.,
running the telco service directly into just the DSL modem -- through
a ferrite, of course)
* Wrapping the DSL modem in aluminum foil
* Swapping out modems
* Looping a few turns of the shielded TP entrance cable through a
Type 31 ferrite at the entrance to the NID
My telco guy has a background of having installed shielded wiring
telephone systems in government buildings near high-power radar
transmitters, so he has a preference for certain shielding
techniques. Unfortunately, keeping 1.8 MHz RF out of DSL links is not
exactly the same problem. He has been bouncing my problem off the
technical staff back at telco HQ, and they have pointed out a few
things, such as: it's the same problem they have with AM broadcast
station interference to DSL in civilized areas; and it's aggravated by
the fact that I'm at about the 3.6-mile point on a DSL path that's
only supposed to extend 3.5 miles....:-)
The Speedstream modems are programmed to quit and reboot if the errors
accumulated in a certain period exceed 30 or so. I've asked the tech
to see if he has any way of reprogramming that number from the central
office or remote switch. Because of the highly intermittent nature of
my transmissions, that change might reduce the aggravation factor for
my family.
Does anyone have other suggestions, short of giving up my SPG
lightning protection and going back to having the telco service enter
the building at the farthest point from my tower? Are there, for
instance, other DSL modems out there that have shown themselves to be
more bulletproof in actual use?
Bud, W2RU
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