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Listing BBSNOISE.TXT

=====[ YOUR SYSTEM HAS NOISE ]==============================================


Written by Bill Noel

Your system has noise!!  Ever heard that from one of your users?  Of
course you have.  And did you have a problem?  Most likely not.  If you
had a noisy line then all of your calls would have been noisy.  Then
where is the problem?  It is in what is known as the trunking network.
The Trunking Network is a series of lines and trunks that connect
switching offices.  All offices do not have direct trunks, so they are
routed through a connection office.  Sometimes these trunks operate on
copper cable, sometimes onT-Carrier, and sometimes on the Fiber Optic
cables that are currently being installed.  Any one of these methods can
cause data problems.  In fact, any carrier system can cause one way data
errors.  That is, the BBS can be seeing errors and the user does not see
them, or vice versa.  The latter problem makes your user know for sure
that your BBS is in trouble.

Trunking Network problems are the most difficult problems to solve.
Southern Bell does not train their Repair Clerks to handle trunking
complaints.  What you should do when you experience data problems to a
certain exchange is listen to a quiet line into that office.  Try to
describe the problem in terms of steady noise, "popping," "frying,"
"other people on the line", etc.  Tell the repair clerk that you always
have this type of problem when calling the 457 exchange when calling
from the 999 exchange.  Tell her this is a trunking problem and to
please really the report to Trunking Maintenance.  Never tell her that
you have a data problem.  Southern Bell does not guarantee data
transmission on non-conditioned lines.  (However, a non-conditioned line
that meets all of their normal residential service requirements will
support data up to 2400 baud with very little problems).  Remember that
when you buy a cheap modem, you get a cheap modem.  Why was it cheap?
Because they left things out like noise filters!  Keep that in mind when
you buy.

But what if you are really having trouble on you line?  Be careful
before calling Ma Bell with a complaint.  If you are not paying them the
$1.00 service charge for House Wire Maintenance, they will hit you with
about $35.00 per hour to fix the problem, or even if they don't fix it
but prove it was you fault.  The mini-jacks located in your house can
cause you a lot of noise problems.  They get all kind of things in them
like smoke, grease, animal hair, and dust.  These things cause the
contacts to corrode.  Corrosion causes noise.  If you have an OHM meter
and the technical skill to use it, lift the house wire from the
terminals and check for high resistance shorts in you house with all of
your modems and phones removed from the jacks.

Noise problems can also come from the carbon blocks located in the small
grey box located where the phone lines enter your house.  Normally this
condition will appear after an electrical storm or high winds when there
may have been currents flowing on the phone lines.  These devices belong
to the phone company and you should not mess with them.
I hope this will shed some light on the subject of noise for you.


Listing NOISE_1.TXT

Modem Noise Killer (alpha version)

With this circuit diagram, some basic tools including a soldering iron, and
four or five 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 fare amount of junk when connecting at that speed. Knowing
that capacitors make good noise filters, I threw this together.

This 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),
and on and on. 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 wizzards out there wanting to offer
any improvements. Let's make this work for everyone!

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

OK, what you' ll need from Radio Shack:

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

1 #279-420 Modular surface mount jack (4 or 6 conductor) $4.49

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

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

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

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 off, open the modular block. You normally just pry them open 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. Now, 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. 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. Well, now that
you've got it built you'll need to test it. First 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:

A. If your modem has two modular plugs in 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. Usually silver in color)

B. 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.

C. 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 ORIGNAL FILE***

ADDITION TO ORIGNAL 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 circuit.

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

Mike McCauley
*** END OF FILE AS I RECEIVED IT ***


To: All
From: Tom Cryar, Baltimore, MD

Before you spend any money to get the parts mentioned above (cheap as they
are), a quick and dirty test will allow you to determine the likelyhood of
success using the resistance-capacitance fix:

(An assumption is made that you have a regular telephone hooked up on the same
line that you use for telecommuncating.  If not, make sure you have one plugged
into the 'phone' jack on your modem, or put a splitter or 'Y' in the line and
hook a phone set onto the line.)


With the extension phone "on-hook" (not in use), place a call to your favorite
NOISY BBS.  You all have one or two in your directory.


Once your modem has established a connection, you will probably see the
familiar mixture of text and garbage on the screen.  If by some miracle you got
a clean line, disconnect and try again.  For this test, you want a noisy line!


While the line is generating garbage to your screen, lift the handset from the
phone which is on your modem line.  You should see an instant reduction in the
amount of garbage on your screen.


If this test reduces the noise content on your line, the resistor-capacitor fix
should help.



I cannot predict what effect the RC fix will have on your normal phone service.
I used to be up on phone line requirements, but much has changed over 15 years.


My personal experience regarding noise confirms that your friendly ("Value on
the Line") phone company is highly un-interested in your problem.  The phone
repairman who called to get details on my reported noise problem told me that
the phone company's "only responsibility was to make sure I got a dial tone
when I lifted the receiver"!  Apparently, successful communications is not a
consideration.

The problem I was having may shed some additional light on the various ways for
the phone company to generate noise instead of data:

The Network Interface Box (phone co. equipment) for my house is on an outside
brick wall which faces east.  The drop line to the pole goes into a junction
box mounted on the east side of the pole.  Since my house is in the city, the
junction box and Network Interface Box are both shaded from the direct rays of
the sun until about 9:30 to 10:00 a.m.

My noise problem seemed to be temperature, time, season and sky dependent: In
the winter, my problem was minimal.  In the summer, it was maximal.  When the
air temperature rose above 80 F, the noise rose accordingly.  When the sky was
cloudy or overcast, the problem was less than when the sun was out in full
force.

In addition to the above, the noise problem was time dependent:  My phone line
was relatively noise-free until about 10:00 to 10:30 a.m., later if it happened
to have been cool overnight.

It doesn't take an Eistein-clone to figure out that something is probably
heating up in the Network Interface or pole junction box.  Most likely since
the junction box is quite old, there is a fair amount of corrosion on the wires
and connectors in the junction box.  When they heat up, the resistance across
the connection goes up.  You can still push a voice signal across the corrosion
but a data signal just ends up with too many bits fouled up.

When I put the extra load of another phone extension onto the line, the phone

company switching equipment sees a lower impedance at my house and pushes a
little more current down the line...often enough to overcome the lousy
connectors.

In fact, I have never gotten around to putting an RC fix onto my own modem line
although it is one of my future projects.

When my line is too noisy to be cleared up by one additional extension on the
line, I connect a second extension on the same line. So far, two extensions
plus the modem load have been sufficient to clear up even the noisiest line I
encounter.


8/12/88
*** end ***



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