Why don't I get 28800 bps (or more) on my connections?

If you see a connection speed of 38400, 57600, or 115200, don't be fooled. This is the serial port speed between your computer and your modem, not the speed between your modem and the modem on the other side of your connection. Reported initial connect speeds won't necessarily be dependable or even comparable from modem to modem or location to location. The reason is that V.34 modems can (and often do) speed shift up and down after the initial connection and do so in a manner dependent on the particular connection, as well as the equipment at each end. Some modems connect at a more conservative speed and then quickly upshift as conditions allow. Other modems connect at a more aggressive speed only to quickly downshift (or worse, lose performance due to excessive errors). Another problem is that software may report the receive speed for certain modems and the transmit speed for other modems, which can be substantially different. It is not possible to monitor the actual modem speed during the connection for most modems. Regardless, the only thing that really counts is net throughput, which can be measured by many communications applications. If you consistently connect at 26400 or above, there may not be much that you can do to increase the performance. It's simply not possible to achieve the highest V.34 speeds on many phone circuits. This is not false advertising. These 28.8 modems are designed to wring as much speed out of the actual real-world connection as possible, and 28800 is only possible in ideal circumstances. If you consistently connect at lower speeds, there may not be much that you can do.
Below are some suggestions on how to optimize your connection:

Make sure that your serial port is locked at 38400 or higher (57600 recommended). This is usually set within your comm application, not the Windows Control Panel.

Try connecting to known good 28800 numbers. This will at least tell you whether the problem is at your end or the other end of the connection. We recommend that you try a number which will provide you with an on-line reading of connection quality from a BBS command.

Watch out for dial-in numbers that are being forwarded to a distant location. Unknown to the general public, many BBSs and ISPs use Call Forwarding to extend their local calling areas. Where location A to location C is a toll call, and an intermediate location B is local to both A and C, Call Forwarding from B to C effectively makes A to C a local call. Although this can work fairly well at lower speeds, the extra connection hop can degrade the signal enough to limit higher speeds.

If possible, test for premises problems. Disconnect all your wiring and equipment from the incoming telco terminating block and hook your modem directly to it. If your connections are better, you have a premises problem that you may be able to isolate and fix. Premises problems, such as faulty wiring and/or equipment like cheap phones and fax machines, are a frequent cause of 28800 connection problems.


If none of this helps, listen carefully to the quality of your voice connections. You must dial a known quiet number, since many otherwise good phone lines exhibit excessive noise until you actually connect (Dialing a single digit is not enough). If you hear more than very faint hiss or hum after you connect, you probably have a line problem. While a quiet line is important, there are other line problems that can reduce your speed, such as Bandwidth, distortion, etc. It is difficult to test for these problems without proper test equipment, but it's still a good idea to listen carefully for audible problems, particularly if you can find a number that will send you test tones. You may be able to get your phone company to improve the quality of your line. When contacting them, it may help to report that you are also having fax problems. Or you can try asking for a data or fax "specialist." Ideally you want the service technician to bring a sophisticated line or transmission test set, not just the basic tester. It may also help to ask for a BERT (bit error rate tester) or "data test set." Sometimes switching to a different cable pair from the CO (central office) will help. In extreme cases, you may have to resort to ordering a new line and canceling the old line. You may be told that you need a special "data" line, more properly called a "conditioned" circuit, which is considerably more expensive than a standard "voice-grade" circuit. Don't waste your money. All you need is a good quality "voice-grade" circuit.
A final note: Add-on noise filters will not help. Your 28800 modem already has all the filtering it can use. An add-on filter will do nothing at best, and it may well make things worse.

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