199 lines
8.8 KiB
Plaintext
199 lines
8.8 KiB
Plaintext
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(word processor parameters LM=8, RM=75, TM=2, BM=2)
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Taken from KeelyNet BBS (214) 324-3501
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Sponsored by Vangard Sciences
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PO BOX 1031
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Mesquite, TX 75150
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There are ABSOLUTELY NO RESTRICTIONS
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on duplicating, publishing or distributing the
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files on KeelyNet except where noted!
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October 26, 1991
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NOISE_1.ASC
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This file shared with KeelyNet courtesy of Matt McFarland.
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--------------------------------------------------------------------
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Modem Noise Killer (alpha version)
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With this circuit diagram, some basic tools including a soldering
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iron, and four or five components from Radio Shack, you should be
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able to cut the noise/garbage that appears on your computer's
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screen.
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I started this project out of frustration at using a US Robotics
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2400 baud modem and getting a fare amount of junk when connecting at
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that speed. Knowing that capacitors make good noise filters, I threw
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this together.
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This is very easy to build, however conditions may be different due
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to modem type, amount of line noise, old or new switching equipment
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(Bell's equipment), and on and on. So it may not work as well for
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you in every case. If it does work, or if you've managed to tweek it
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to your computer/modem setup I' d like to hear from you.
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I'd also appreciate any of you electronic wizzards out there wanting
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to offer any improvements. Let's make this work for everyone!
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Please read this entire message and see if you understand it before
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you begin.
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OK, what you' ll need from Radio Shack:
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1 - #279-374 Modular line cord if you don't already have one.
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You won't need one if your phone has a modular plug in its
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base. $4.95
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1 - #279-420 Modular surface mount jack (4 or 6 conductor)
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$4.49
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1 - #271-1720 Potentiometer. This is a 5k audio taper variable
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resistor. $1.09
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1 - #272-1055 Capacitor. Any non-polarized 1.0 to 1.5 uf cap
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should do. Paper, Mylar, or metal film caps should be used,
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although #272-996 may work as well.
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(272-996 is a non-polarized electrolytic cap) $.79
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1 - 100 ohm resistor - quarter or half watt. $.19
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Page 1
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1 - #279-357 Y-type or duplex modular connector. Don't buy this
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until you've read the section on connecting the Noise
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Killer below. (A, B,or C) $4.95
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First off, open the modular block. You normally just pry them open
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with a screwdriver. Inside you'll find up to 6 wires.
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Very carefully cut out all but the green and red wires. The ones
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you'll be removing should be black, yellow, white, and blue. These
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wires won't be needed and may be in the way. So cut them as close
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to where they enter the plug as possible. The other end of these
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wires have a spade lug connector that is screwed into the plastic.
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Unscrew and remove that end of the wires as well. Now, you should
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have two wires left. Green and red. Solder one end of the capacitor
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to the green wire. Solder the other end of the capacitor to the
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center lug of the potentiometer (there are three lugs on this
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critter). Solder one end of the resistor to the red wire.
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You may want to shorten the leads of the resistor first. Solder the
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other end of the resistor to either one of the remaining outside
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lugs of the potentiometer. Doesn't matter which. Now to wrap it up,
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make a hole in the lid of the mod block to stick the shaft of the
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potentiometer through.
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Don't make this hole dead center as the other parts may not fit into
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the body of the mod block if you do. See how things will fit in
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order to find where the hole will go.
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Well, now that you've got it built you'll need to test it. First
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twist the shaft on the potentiometer until it stops. You won't know
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which way to turn it until later.
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It doesn't matter which way now. You also need to determine where to
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plug the Noise Killer onto the telephone line. It can be done by one
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of several ways:
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A. If your modem has two modular plugs in back, connect the
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Noise Killer into one of them using a line cord. (a line cord
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is a straight cord that connects a phone to the wall outlet.
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Usually silver in color)
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B. If your phone is modular, you can unplug the cord from the
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back of it after you're on-line and plug the cord into the
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Noise Killer.
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C. You may have to buy a Y-type modular adaptor. Plug the
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adaptor into a wall outlet, plug the modem into one side and
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the Noise Killer into the other. Call a BBS that has known
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noise problems.
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After you've connected and garbage begins to appear, plug the Noise
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Killer into the phone line as described above. If you have turned
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the shaft on the potentiometer the wrong way you'll find out now.
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You may get a lot of garbage or even disconnected. If this happens,
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turn the shaft the other way until it stops and try again. If you
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don't notice much difference when you plug the Noise Killer in, that
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may be a good sign.
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Page 2
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Type in a few commands and look for garbage characters on the
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screen. If there still is, turn the shaft slowly until most of it is
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gone. If nothing seems to happen at all, turn the shaft slowly from
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one side to the other. You should get plenty of garbage or
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disconnected at some point. If you don't, reread this message to
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make sure you've connected it right.
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***END OF ORIGNAL FILE***
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ADDITION TO ORIGINAL FILE - 2/29/88 - Mike McCauley - CIS 71505,1173
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First, a personal recomendation. _THIS WORKS!!!_ I have been
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plagued with noise at 2400 for some time. I went round and round
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with Ma Bell on it, and after they sent out several "repair persons"
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who were, to be kind, of limited help in the matter, I threw in the
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towel.
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I saw this file on a board up east a few days ago, and thought I'd
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bite. Threw the gismo together in about 10 minutes, took another
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five to adjust the pot for best results on my worst conection, and
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guess what? No more worst connection! A few pointers:
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1) The pot need not be either 5K or audio taper. I used a 10K
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15 turn trim pot. Suggest you use what is handy.
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2) I used 2MFD's of capacitance (two 1MFD's in parallel) Two
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R.S. p/n 272-1055 work fine. Remember that about 90 Volts
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will appear across red & green at ring, so the caps should
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be rated at 100VDC+.
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3) I ended up with a final series resistance value (100 ohm +
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pot) of 2.75K.
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I speculate that one could probably use 2MFD and a fixed 2.7K
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resistor and do the job 90% of the time. The adjustment of the pot
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is not very critical. Changes of +/- 1K made little difference in
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the performance of the circuit.
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Hope it works as well for you as it did for me.
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Mike McCauley
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--------------------------------------------------------------------
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If you have comments or other information relating to such topics
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as this paper covers, please upload to KeelyNet or send to the
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Vangard Sciences address as listed on the first page.
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Thank you for your consideration, interest and support.
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Jerry W. Decker.........Ron Barker...........Chuck Henderson
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Vangard Sciences/KeelyNet
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--------------------------------------------------------------------
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If we can be of service, you may contact
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Jerry at (214) 324-8741 or Ron at (214) 242-9346
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--------------------------------------------------------------------
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Page 4
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