Connect Speeds

[boywonder]

Something caused my connect speed to drop from 46 to 37.2Kbps

Went around the house and made sure nothing is plugged in double checked my newly wired line everything is secure. Think the phone company jacked my line up

Any suggestions

[cholla]

Probably just network traffic or sometimes bad weather causes a slowdown in dial-up.If its stays down then maybe the phone company or your ISP.I suspect mine of keeping my speed down because it used to be faster.Both will tell you they don't "cap" dial-up .

[boywonder]

I dont beleive its my ISP I tried both NetZero and Highstream. Getting the same results this morning as well.

We are not having any adverse weather conditions so my telco must have did something.

My SNR dropped consideriably too.

Oh well, I'm flying out to Oklahoma this sun  and hopefully it will magically fix itself by the time I'm back

[cholla]

boywonder;You sure picked a cold weekend to visit Oklahoma.Since I live in the Texas Panhandle Oklahoma has some simular weather depending on the part of OK.

It probably is a line problem if the SNR dropped There are a lot of causes for this.I'm posting a lot of info on it .Unfortunatly not a fix for it.

An Introduction to Load Coils and Bridge Taps

There seems to be some confusion as to what can be causing the new modems not to reach the Golden ring of 56K baud rates. I may be able to clear some of this up.It probably

won't help fix the problem but at least we all point our finger at the same cause and effect.

Load Coils

Load coils (impedance matching transformers) are placed along the length of a long Telco POTs line that exceeds the 6000ft termination spec. The twisted pair of an analog line is a "balanced pair" interface with specific impedance terminations 600 or 900 ohms. The impedance loads are initially found in the "Line Card" at the telco switch and the telephone or modem. Impedance load is very different from loop resistance.Those terminations are

engineered for the specific 600 or 900 ohm value to match the Amplitude and Frequency characteristics of the analog signal. The proper impedance termination is vital  to absorb

the maximum possible power on the line. If the impedance loads are not properly matched

to the signal, they will only absorb part of of the signal and cause an improper signal transfer

to the switches receiver circuitry. The problem starts to become evident when you wonder this - "If the energy of the signal is only partially absorbed, what happens to the stuff that's not  absorbed?"

All energy that is not absorbed by the termination load reflects back on to the copper pair and begins to interfere with the original signal. Because the reflected signal is usually out of phase from the original signal, this starts to cause "common mode rejection" or cancellation or loss of Amplitude at specific "standing wave" frequencies and their mathematical derivatives. The net effect of that is, the original signal begins to get crippled by its own    reflection.

The Evil Load Coils are placed in the circuit at specific intervals (varies depending on wire gauge and cable bundling variables) to reduce the effective capacitance of the extended copper loop and therefore provide a higher level of predictability across the copper segment. Remember, impedance matching, in theory, only works if you can predict the signal characteristics of the waveform being impeded. Anything that drastically alters the characteristics of the waveform will make the circuits termination less effective in absorbing the maximum signal.

The argument is that, three discrete segments of 6,000 feet copper has less negative capacitive effects than a single copper segment that is perhaps 18,000 feet long. Therefore, in a long copper loop, Load coils are placed at strategic points to reduce the negative effects that capacitance will have on the signals characteristics. Capacitance is the enemy of high BAUDrate applications. Amplitude can be overcome with amplifiers, Capacitance is much harder to control cheaply.

This load coil works wonderfully for voice, however; load coils, with their purpose to limit excess capacitance, also greatly limits the frequency spectrum available to the end devices. By the way, load coils also help restrict impulse noise or interference from one copper segment to adjacent copper segment. So in effect may reduce the additional noise characteristics from loop interference. Now back to the limit of frequencies.

There are a few variables that affects this discovery either positive or negative. But in general, placing a load coil in a Telco voice line reduces the effective bandwidth by chopping off the top 25 percent of the available frequencies. If you are to take a tone generator to the lines you would see the highest quality signal at approximately 1,000 to 2,000 Hz. When the

tone generator reached 2900 Hz there would be a significant "role off" of over 12dB per octave. This reduction explains why you can't use load coils in digital circuits. As a matter of reference if you examined a T1 signal with a scope it would look like a very phase distorted 772KHz analog signal. Certainly any facility that limited the bandwidth to 2900 Hz would

seriously choke a signal running at 772KHz. The same holds true for ISDN BRI which has an effective signal rate of approximately 40KHz.

So, it becomes obvious that load coils can cripple the high speed signal. Please note, that removing the load coils will only make the signal worse. Because of the nature and characteristics of how modems manipulate an analog signal, removing the load coils will just cause exponentially more distortion across the copper segment. If you want to remove the load coils you must completely re engineer the way the data signal is presented to the copper pair. Thats what they did with ISDN. I don't think anybody is really up for the challenge at this point.

Bridge Taps

These little bastards are perhaps the most annoying and offensive of all the anomalies found in a Telco copper segment. They are by far the number one problem you all have getting modems to connect and stay connected at high speeds. Unfortunately they are riddled throughout most residential neighborhoods and corporate business parks.

W hen the phone company runs a cable down the street the cable may extend a mile or so passed your house. Although no other house or device is using your specific copper pair, the pair runs out the length of the cable. All an installer does is take the wires that come from your demarc, drag them out to a junction box or splice box on a poll or pedestal and "Tap" the wires coming from your house on to a spare copper pair that runs out the length of the cable. They do not cut the cable pair at the junction box just incase they have to use the same pair for one of your neighbors down the road when you move out. Also, in order not to drastically reduce the amplitude and of the signal coming from your telephone they do not to terminate the extended cable end either.

That means there may be a one mile cable running from the central office out past your house and your telephone line is simply tapped into the middle of it. It's sort of like having an additional half-mile antenna picking up all the garbage in the airand feeding it to your telephone equipment.

Assuming for a moment we can deal with the additional idle channel noise on the copper facility, which even the most unqualified lineman can test for, (but if you ask him what he's testing for he probably can't tell you), and tell you some story how your line is the quietest line on the street, the next hurdle beyond the noise is the reflected signal coming back off of the half-mile unterminated antenna they built just for you at no additional charge.

When an electrical signal hits the end of a wire it has to go somewhere. If there is no impedance load to absorb the signal,then the signal in its entirety gets reflected back over the entire copper segment. The signal that comes from your modem headed for the central office arrives at a specific time interval and the reflected signal coming back off the unterminated copper extension comes then just behind yours causing your signal to appear phase distorted.

When two out of phase signals are received at a certain impedance load of a cause a rejection affects and begin to cancel each other out. If the signals arrives 180 degrees out of phase your signal can be canceled out completely. The more the second reflected signal it is closer to 180 degrees the more the signal will be attenuated and phase distorted. At lower

frequencies problem is not terribly dramatic as these reflections are only fractions of a waveform out of phase. But when you make the waveform's smaller as is the case with higher frequencies the problem becomes exponentially more apparent.

Phase is much more an issue with smaller, shorter or higher frequency wave forms. In a nutshell, we are screwed.

Even when you can get them to, a customers residence and have a line tested, they DO NOT test the frequency response of the line. They perform the following two tests..

The first test it is a 1,000 Hz tone coming from the central office switch and measured at the customers demark for attenuation. The 1,000 Hz tone is significant because it is smack in the middle of the voice frequency range (your vocal cords cannot really make sound above 3000 Hz). Assuming they have their test equipment Setup and terminated properly they

can get a dB measurement of the 1,000 Hz tone and say that is in some specified range. Please note that there are no documented specified ranges for analog voice lines using this test setup. The results of this test are merely to identify the signal level coming in. I believe somewhere between -6dbm and -20dbm is acceptable but I'm not really sure.

the second test they may perform it is terminating the line and doing a Cmsg noise test measuring the title channel noise on the facility with no signal provided. Ideally there are some specifications that identify how much of this noise is tolerable

for a voice circuit but I'm sure the tester doesn't know where that acceptable threshold is. The tester might as well pickup of the telephone receiver and blow in to it to see if the line passes mustard....

The problem was this noise test is that putting a signal on the line generates additional noise and interference that the modems have to contend with all the time. This noise is not present when the line is just quietly terminated at each end.

The test I would really like them to perform is a frequencies sweep between 300 and 4000 Hz and a Bridge tapped test to determine how out of phase my signal may look by the time it gets to the central office and whether it falls into specific characteristics too. If these tests are routinely performed on the TOLL grade facilities between telco central offices they should also be performed at the customers request on the drop side of the switched circuit. It time consuming, its out of the question.

I've had the conversation with several Telco repair supervisors about lifting Bridge taps and performing signal-to-noise ratio tests. The conversation ends when they say "we do not guarantee data of above 2400 Baud". They are right too this isnot a conditioned data line and I have no recourse.

Incidentally, this bridge tap problem became apparent right after 9600 baud modem's where replaced with 14.4k modems.

The problem then got escalated with 28.8 and now begins to take on monstrous effects on the new super modems.

It is an interesting argument, putting these modems on voice lines and pushing the envelope beyond their engineered usefulness. The real culprits in this equation is not the Telcos. It is the bastard scum bag modem manufacturers pulling the wool over the eyes of the consumer and expecting us to make it work and/or absorb all of the S#!t when it doesn't Telcos do not want you to use high speed modems on your voice lines anyway so you'll find a very limited support from that camp.

Signal to Noise Ratio lower than 37 dB indicates a call with reduced quality. You need a

SNR of at least 37 dB in order to sustain a 28.8 kB/s modem connection. You need a SNR of at least 38 or 39 dB to sustain a 33.6 kB/s connection.

For you technical types, here are some of the phone line bandwidth, frequency response and

related technical parameters expected by the new 56k modems:

3600 Hz of usable bandwidth between 150 - 3750 Hz with

-Less than 10 dB rolloff at the low end between 150 and 300 Hz

-Less than 24 dB rolloff at the high end between 3450 and 3750 Hz

-Better than -50 dB receive level at 3750 Hz

-No load coils

-No bridge taps

-No wire gauge changes

-Less than 43 dB attenuation end-to-end

-Maximum of one (1) digital-to-analog transition

Any telephone company engineer will tell you these are some really extraordinary parameters

to expect from the average subscriber's phone line.

The POTS line consists of two wires called tip and ring. These two wires provide DC current

to power the telephone electronics, AC current to ring the telephone bell or electronic ringer, and a full duplex balanced voice path.

This is a closed loop, balanced system not referenced to earth ground. The POTS phone line, with all phones on-hook, should measure around 48 volts DC. Taking a phone off-hook creates a DC signal path across the pair, which is detected as loop current back at the central office. This drops the voltage measured at the phone down to about 3 to 9 volts. An off-hook telephone typically draws about 15 to 20 milliamps of DC current to operate, at a DC resistance around 180 ohms. The remaining voltage drop occurs over the copper wire path and over the telephone company circuits. These circuits provide from 200 to 400 ohms of series resistance to protect from short circuits and decouple the audio signals.

POTS Line Characteristics:

Bandwidth: 180 Hz to 3.2 KHz

The low end is rolled off early to stay away from the 60 Hz region. Also, telecom isolation and hybrid transformers would be much more bulky, (and expensive) if they had to carry signals down to 20 Hz.

The high end cut off is more critical. Voice on the telephone network is digitized at 8 KHz sampling rate which means that any signal above 4 KHz will be aliased back as noise in the voice band. Most voice CODECs roll off at about -25dB at 4 KHz with a -3dB down point around 3.2 KHz. The phone company decided years ago that the 180 Hz to 3.2 KHz range would be sufficient for speech intelligibility while allowing them to multiplex many calls over coax and twisted pair.

Signal to Noise: Approximately 45 dB

This is not as easy to quantify because noise comes in many forms, such as electrical interference from fluorescent fixtures or hiss from the many amplifier stages in the voice path.

Speech correlated noise can be introduced from non-linear speech coding and compression algorithms. Crosstalk from other conversations is another form of noise. The phone company uses 8 bit mulaw nonlinear coding which yields about 12 bits of

dynamic range. The bottom line is that you can never count on more than about 45 dB signal to noise ratio.

Signal Levels: -9 dBm average speech across tip/ring. Speech peaks out to +4 dBm can be measured at the phone, but anything over 0dBm at the central office will be clipped. The FCC requires that all telephone audio interconnect equipment limit speech to -9dBm, averaged over 3 seconds. Consult FCC Part 68 requirements for all the details.

Resistance reduces the current so increases the loss.

Capacitance effectivly short circuits the line more as frequencies increase so increasing loss.

Inductance resists current flow more as frequencies get higher thus increasing the loss.

Everything that carries electricity has what is known as "Resistance". This is measured in "Ohms" and resistance impedes the flow of current in a conductor.

Because your connection is two wires twisted together it also has some "Capacitance" between the wires. A capacitor is an electrical component and there is more current passed through it as the frequency gets higher.

also your pair of wires has yet another characteristic called "Inductance" and inductance allows less current to flow through it as the frequency gets higher.

[boywonder]

cholla, You were right about being cold. My flight was delayed out of Dallas Ft. Worth because they had to de- ice every plane flying out. I think they said it was 29 deg. Damn and I thought Ohio got cold .

Well I'm back home now the problems I was haveing before are gone and infact my connect speed/ downloads have increased check it out.

:::.. Download Stats ..:::

Connection is:: 51 Kbps about 0.1 Mbps (tested with 97 kB)

Download Speed is:: 6 kB/s

Tested From:: https://testmy.net  (main)

Test Time:: 2006/03/06 - 10:11am

Bottom Line:: 1X faster than 56K 1MB Download in 170.67 sec

Diagnosis: May need help : running at only 2.41 % of your hosts average (qwest.net)

Validation Link:: https://testmy.net/stats/id-GT1WQJHMP

[brokersdad]

This good or bad?     Back along time ago when I was calling constantly complaining to my ISP about me getting booted while gaming, the gave me a  extra initialization command to put in the extras line in my modems advanced settings. I hadn't tried it in a while so reading all thsi stuff sparked my memory about it. I did a test before I entered that code and if I read it right I was @ 4kbps dload and connecting @42.5...now it's saying  when I connect that im  @115.2 kps

Don't know if thats possible but thats what it's showing.  Btw, im new to the forums in case any of you didn't see my post in the general section, nice to meet you all.   I feel quite stupid in here after reading what you guys know..man, it's hard to grasp alot of what you talk about! 

::::::::::.. testmy.net test results ..::::::::::

Download Connection is:: 48 Kbps about 0.05 Mbps (tested with 97 kB)

Download Speed is:: 6 kB/s

Upload Connection is:: 23 Kbps about 0 Mbps (tested with 97 kB)

Upload Speed is:: 3 kB/s

Tested From:: https://testmy.net (Server 2)

Test Time:: 2007/01/08 - 9:03pm

D-Validation Link:: https://testmy.net/stats/id-0X8MZR314

U-Validation Link:: https://testmy.net/stats/id-A1PQMDWU2

User Agent:: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)

[dlewis23]

This good or bad?    Back along time ago when I was calling constantly complaining to my ISP about me getting booted while gaming, the gave me a  extra initialization command to put in the extras line in my modems advanced settings. I hadn't tried it in a while so reading all thsi stuff sparked my memory about it. I did a test before I entered that code and if I read it right I was @ 4kbps dload and connecting @42.5...now it's saying  when I connect that im  @115.2 kps

Don't know if thats possible but thats what it's showing.  Btw, im new to the forums in case any of you didn't see my post in the general section, nice to meet you all.   I feel quite stupid in here after reading what you guys know..man, it's hard to grasp alot of what you talk about! 

::::::::::.. testmy.net test results ..::::::::::

Download Connection is:: 48 Kbps about 0.05 Mbps (tested with 97 kB)

Download Speed is:: 6 kB/s

Upload Connection is:: 23 Kbps about 0 Mbps (tested with 97 kB)

Upload Speed is:: 3 kB/s

Tested From:: https://testmy.net (Server 2)

Test Time:: 2007/01/08 - 9:03pm

D-Validation Link:: https://testmy.net/stats/id-0X8MZR314

U-Validation Link:: https://testmy.net/stats/id-A1PQMDWU2

User Agent:: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)

dont feel stupid at all.

Those are good speeds for dialup. there is no way your getting connected at 115.2kbps over dialup, the modem can only go up to 54.kbps.

[tommie gorman]

Unless you are ROM-DOS. Or modem bond. 

But anyway, we truly do not want anyone to feel stupid. That is my job, please do not take it away. 

Any other questions, just feel free to post. They still let me do that once in a while.

(at night I steal the key and post) 

[brokersdad]

Lol..ok tommie.  As for me connecting at 115.2kbps, I didn't figure that was actual when I posted it, but for whatever reason, when I hover over my connection icon in my taskbar it says im connected at that. Again, that is since I put that code in my ISP told me, before that I was always 42.5 kbps

[boywonder]

simi-dimpskin ~ welcome to the forums. I'm currious what init code did you put in?

[tommie gorman]

Don't forget simi-dimpskin, the best way to check actual D/L speeds is when downloading something, it will show in the box.  If you are not sure of what it means, in the top of the TMN browser they have a conversion calculator and  table for you to use.