N1BUG wrote:
>I knew DSL modems and 160m don't mix, but I am trying it anyway. The problem,
>of
>course, is that when I transmit on topband the modem loses sync. It
>only takes 50 watts to do it.
>
>
To the best of my knowledge, 160 is the only band that caused problems
with mt DSL modem -- but only when running my amp.
>Would winding several turns of the DSL and/or modem power cables on
>a toroid potentially be helpful?
>
It was very helpful here. But connecting your DSL modem to the phone
line in a different part of the house may help, too. Initially my DSL
modem was plugged into a phone jack less than 30 feet from the base of
my 160 vertical, and I subsequently did move it farther away, but I
successfully cleaned up the common mode ingress with toroids before
moving the modem.
>Would 43 or 77 material be better?
>
Good question. I went to my junk box and used my last two large I.D.
toroids. All I know about them is they're black.
>Any other thoughts?
>
>
Don't forget possible common mode ingress via any other cables attached
to your DSL modem -- such as any ethernet cables to PCs or wireless
routers, and the telephone line itself.
>Is it possible to use a low pass filter on the DSL line to attenuate
>1.8 MHz while letting DSL signals pass? I've never seen nor heard of
>such a device...
>
>
First you might want to look at the DSL statistics screen for your DSL
modem. My modem (supplied by Frontier / Citizens) is a SpeedStream
5200. I can go to "http://192.168.254.254"; with my browser and check
various kinds of status reports and stats for the unit. In particular,
I can see that my attenuation (from the telco C.O. or nearest DSL
switch) is 48.5 dB and my SNR is 14.5 dB. My telco guys recently
"upgraded" my installation so I would attain this level of performance
by doing four things:
a. Replaced my 2-year-0ld SS5200 with a new SS5200. (The newer
model has an asymmetrical plastic case with a molded stand built into
one end, for standing the unit on end (i.e., vertical row of LEDs), if
you wish.
b. Removed my DSL filters at each telephone jack in the house and
installed a "whole house" DSL filter in the main phone line in the
basement. A special "DSL only" line of genuine telco twisted pairs was
then run from this filter to a _single_ outlet for my DSL modem, located
wherever I chose in my house.
c. Forced me to remove all "flat" telephone cables between my
telco DSL wall jack and my DSL modem. Flat cables are _not_ twisted pairs.
d. Rewired my existing telco wiring so there were no "stubs"
between the telco interface network on the outside of my house and the
new whole-house DSL filter. At DSL frequencies it is imperative to
think of your telco line as an RF transmission line, and treat it
accordingly.
The aggregate effect of these changes was to reduce my total line
attenuation and increase my SNR by 3 dB or more. I am sure that my
susceptibility to 160-meter ingress also improved as a result of these
changes.
I am 3.5 miles from my telco's DSL switch -- pretty near the limit
they're willing to consider. The telco tech told me that total line
attenuation over 50 dB (I was at 52 dB before they walked in the door)
is a recipe for marginal DSL operation -- even in households with no hams.
I am routinely getting download speeds of between 1.3 and 2.2 Mbps now.
Bud, W2RU
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