TIFILES€@PÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊSÊS"Modem Noise Killer (alpha version) KWith this circuit diagram, some basic tools including a soldering iron, andGfour or five components from Radio Shack, you should be able to cut the5noise/garbage that appears on your computer's screen. ÿJI started this project out of frustration at using a US Robotics 2400 baudNmodem and getting a fare amount of junk when connecting at that speed. Knowing?that capacitors make good noise filters, I threw this together. ÿLThis is very easy to build, however conditions may be different due to modemNtype, amount of line noise, old or new switching equipment (Bell's equipment),Kand on and on. So it may not work as well for you in every case. If it doesÿMwork, or if you've managed to tweek it to your computer/modem setup I' d liketo hear from you. MI'd also appreciate any of you electronic wizzards out there wanting to offer4any improvements. Let's make this work for everyone! ÿNPlease read this entire message and see if you understand it before you begin. 'OK, what you' ll need from Radio Shack: N1 #279-374 Modular line cord if you don't already have one. You won't need one3if your phone has a modular plug in its base. $4.95ÿ >1 #279-420 Modular surface mount jack (4 or 6 conductor) $4.49 L1 #271-1720 Potentiometer. This is a 5k audio taper variable resistor. $1.09 L1 #272-1055 Capacitor. Any non-polarized 1.0 to 1.5 uf cap should do. Paper,ÿMMylar, or metal film caps should be used, although #272-996 may work as well.2(272-996 is a non-polarized electrolytic cap) $.79 /1 100 ohm resistor - quarter or half watt. $.19 ÿO1 #279-357 Y-type or duplex modular connector. Don't buy this until you've readCthe section on connecting the Noise Killer below. (A, B,or C) $4.95 IFirst off, open the modular block. You normally just pry them open with aÿMscrewdriver. Inside you'll find up to 6 wires. Very carefully cut out all butMthe green and red wires. The ones you'll be removing should be black, yellow,Owhite, and blue. These wires won't be needed and may be in the way. So cut themÿOas close to where they enter the plug as possible. The other end of these wiresOhave a spade lug connector that is screwed into the plastic. Unscrew and removeMthat end of the wires as well. Now, you should have two wires left. Green andÿOred. Solder one end of the capacitor to the green wire. Solder the other end ofMthe capacitor to the center lug of the potentiometer (there are three lugs onNthis critter). Solder one end of the resistor to the red wire. You may want toÿMshorten the leads of the resistor first. Solder the other end of the resistorIto either one of the remaining outside lugs of the potentiometer. Doesn'tKmatter which. Now to wrap it up, make a hole in the lid of the mod block toÿNstick the shaft of the potentiometer through. Don't make this hole dead centerLas the other parts may not fit into the body of the mod block if you do. SeeKhow things will fit in order to find where the hole will go. Well, now thatÿHyou've got it built you'll need to test it. First twist the shaft on theNpotentiometer until it stops. You won't know which way to turn it until later.MIt doesn't matter which way now. You also need to determine where to plug theÿLNoise Killer onto the telephone line. It can be done by one of several ways: MA. If your modem has two modular plugs in back, connect the Noise Killer intoNone of them using a line cord. (a line cord is a straight cord that connects aÿ2phone to the wall outlet. Usually silver in color) NB. If your phone is modular, you can unplug the cord from the back of it after7you're on-line and plug the cord into the Noise Killer. ÿMC. You may have to buy a Y-type modular adaptor. Plug the adaptor into a wallNoutlet, plug the modem into one side and the Noise Killer into the other. CallNa BBS that has known noise problems. After you've connected and garbage beginsÿOto appear, plug the Noise Killer into the phone line as described above. If youMhave turned the shaft on the potentiometer the wrong way you'll find out now.LYou may get a lot of garbage or even disconnected. If this happens, turn theÿJshaft the other way until it stops and try again. If you don't notice muchNdifference when you plug the Noise Killer in, that may be a good sign. Type inLa few commands and look for garbage characters on the screen. If there stillÿNis, turn the shaft slowly until most of it is gone. If nothing seems to happenOat all, turn the shaft slowly from one side to the other. You should get plentyNof garbage or disconnected at some point. If you don't, reread this message toÿ$make sure you've connected it right. ***END OF ORIGNAL FILE*** CADDITION TO ORIGNAL FILE - 2/29/88 - Mike McCauley - CIS 71505,1173 JFirst, a personal recomendation. _THIS WORKS!!!_ I have been plagued withÿKnoise at 2400 for some time. I went round and round with Ma Bell on it, andMafter they sent out several "repair persons" who were, to be kind, of limitedLhelp in the matter, I threw in the towel. I saw this file on a board up eastÿJa few days ago, and thought I'd bite. Threw the gismo together in about 10Iminutes, took another five to adjust the pot for best results on my worstCconection, and guess what? No more worst connecion! A few pointers: ÿO1) The pot need not be either 5K or audio taper. I used a 10K 15 turn trim pot.! Suggest you use what is handy.N2) I used 2MFD's of capacitance (two 1MFD's in parallel) Two R.S. p/n 272-1055ÿL work fine. Remember that about 90 Volts will appear across red & green at0 ring, so the caps should be rated at 100VDC+.L3) I ended up with a final series resistance value (100 ohm + pot) of 2.75K.ÿM I speculate that one could probably use 2MFD and a fixed 2.7K resistor andN do the job 90% of the time. The adjustment of the pot is not very critical.N Changes of +/- 1K made little difference in the performance of the circuit. ÿ/Hope it works as well for you as it did for me. Mike McCauleyÿ