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TUCoPS :: Phreaking General Information :: pppv04.txt

Modem Noise Bomber

                           Proudly Present
                      Phucked Phreak Production
*708/808-7629**       **Saturday-February 16, 1991**            **Vol #4*
**                                                                     **
*                          Modem Noise Bomber                           *
**                                                                     **
*                        Borrowed By:The Wizard                         *
**                                                                     **
*                CopyMUCH 1991 (M) Phucked Phreak Productions           *

 "Congress shall make no law respecting an establishment of religion, or
 prohibitting the free excercise thereof; or abbridging the freedom of
 speech or of the press; or of the right of the people peaceably to
 assemble, and to petition the Goverment for a redress of grievances"

Under the above Law set forth in the First Amendment To The Constution
Of The United States Of America, The Author releases this work into the


This was taken from an article in TRS Link magazine, ((issue 13, I think.))

Don't charge to distribute it.  That would be illegal.  ;)

**VOL # 4**

                      Modem Noise Killer (alpha version)

             In  this  project,   with  some  basic  tools  and  a  few
        components from  Radio Shack,  you  should be  able to  cut the
        noise/garbage that appears on your computer's screen. I started
        this project out  of frustration  at using  a US  Robotics 2400
        baud modem and getting a fair amount of junk when connecting at
        that speed.  Knowing that capacitors make good noise filters, I
        threw this together.

             It is  very  easy  to  build,  however  conditions  may be
        different due to modem type,  amount of line noise,  old or new
        switching equipment (Bell's equipment), etc. So it may not work
        as well for you in every  case.  If it does work,  or if you've
        managed to tweek it  to your  computer/modem setup  I'd like to
        hear from  you.  I'd  also  appreciate  any  of  you electronic
        wizards  out  there wanting  to offer  any improvements.  Let's
        make this work for everyone!

             Please read this entire file and see if you understand
        it before you begin.

             OK. This is what you'll need from Radio Shack:

        a) 1 #279-374 Modular line cord  if you don't already have one.
           You won't need one  if your phone has  a modular plug in its
           base. $4.95

        b) 1 #279-420  Modular surface  mount jack  (4 or  6 conductor)

        c) 1 #271-1720 Potentiometer. This is a 5k audio taper variable
           resistor. $1.09

        d) 1 #272-1055 Capacitor.  Any non-polarized  1.0 to 1.5 uf cap
           should do. Paper,  Mylar, or metal film caps should be used,
           although #272-996  may  work  as  well.  (272-996  is a non-
           polarized electrolytic cap) $.79

        e) 1 100 ohm resistor - quarter or half watt. $.19

        f) 1 #279-357  Y-type or  duplex modular  connector.  Don't buy
           this until you've  read the section  on connecting the Noise
           Killer below. (A, B,or C) $4.95

             First,  pry open the  modular  block  with  a screwdriver.
        Inside you'll find up  to 6 wires.  Very  carefully cut out all
        but the green and red wires. The ones you'll be removing should
        be black, yellow,  white, and blue. These wires won't be needed
        and may be in the way. So cut them as close to where they enter
        the plug as possible. The other end of these wires have a spade
        lug connector that  is screwed  into the  plastic.  Unscrew and
        remove that end of the wires as well.

             You should have two wires left.  Green and red. Solder one
        end of the capacitor to the green wire. Solder the other end of
        the capacitor to the center lug of the potentiometer (there are
        three lugs on this critter).  Solder one end of the resistor to
        the red wire. You may want to shorten the leads of the resistor
        first.  Solder the other end  of the resistor  to either one of
        the remaining  outside lugs  of the  potentiometer.  It doesn't
        matter which.

             Now to wrap it up, make a hole in the lid of the mod block
        to stick the  shaft of  the potentiometer  through.  Don't make
        this hole dead center  as the other parts  may not fit into the
        body of the mod  block if you  do.  See how things  will fit in
        order to find where the hole will go.

             Now that you've got it built you'll need to test it. Twist
        the shaft on the potentiometer  until it stops.  You won't know
        which way to turn it  until later.  It doesn't matter which way
        now.  You also need to determine where to plug the Noise Killer
        onto the telephone line. It can be done by one of several ways:

        1) If your modem has two modular plugs in the back, connect the
           Noise Killer into one of them using a line cord. A line cord
           is a straight cord that connects a phone to the wall outlet.

        2) If your phone is modular,  you  can unplug the cord from the
           back of it after  you're on-line and plug  the cord into the
           Noise Killer.

        3) You may have  to  buy  a  Y-type  modular adaptor.  Plug the
           adaptor into a wall outlet, plug the modem into one side and
           the Noise Killer into the  other.  Call a BBS that has known
           noise problems. After you've connected and garbage begins to
           appear,  plug the  Noise  Killer  into  the  phone  line  as
           described  above.  If  you  have  turned  the  shaft  on the
           potentiometer the wrong way you'll find out now. You may get
           a lot of garbage or even disconnected. If this happens, turn
           the shaft the other way until it stops and try again. If you
           don't notice much difference when  you plug the Noise Killer
           in, that may be a good sign. Type in a few commands and look
           for garbage characters  on the  screen.  If there  still is,
           turn the shaft slowly until  most of it is gone.  If nothing
           seems to happen at all,  turn the shaft slowly from one side
           to  the  other.   You  should  get   plenty  of  garbage  or
           disconnected  at  some  point.  If  you  don't,  reread this
           message to make sure you've connected it right.

                         *** END OF ORIGINAL FILE ***

                      ADDITION TO ORIGINAL FILE - 2/29/88

                        Mike McCauley - CIS 71505,1173

             First,  a personal recomendation.  _THIS WORKS!!!_  I have
        been plagued with noise at 2400 for some time. I went round and
        round with Ma Bell  on  it,  and  after  they  sent out several
        "repair persons" who were,  to be kind,  of limited help in the
        matter,  I threw in the  towel.  I saw this file  on a board up
        east a few  days ago,  and  thought I'd  bite.  Threw the gismo
        together in about 10 minutes,  took  another five to adjust the
        pot for best results on my worst conection,  and guess what? No
        more worst connecion! A few pointers:

        1) The pot need not be either  5K or audio taper.  I used a 10K
           15 turn trim pot. Suggest you use what is handy.

        2) I used 2MFD's  of capacitance  (two 1MFD's  in parallel) Two
           R.S.  p/n 272-1055 work fine.  Remember  that about 90 Volts
           will appear across red &  green at ring,  so the caps should
           be rated at 100VDC+.

        3) I ended up with  a final series resistance  value (100 ohm +
           pot) of 2.75K.  I speculate that one could probably use 2MFD
           and a fixed  2.7K resistor and  do the job  90% of the time.
           The adjustment of the pot  is not very critical.  Changes of
           +/- 1K made  little  difference  in  the  performance of the

                Hope it works as well for you as it did for me.

                                  Mike McCauley

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