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Re: Topband: 160m vs DSL modem

To: Topband <topband@contesting.com>
Subject: Re: Topband: 160m vs DSL modem
From: W2RU - Bud Hippisley <W2RU@frontiernet.net>
Date: Sun, 23 Oct 2005 02:45:57 +0000
List-post: <mailto:topband@contesting.com>
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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