Modem card configured to compensate for power supply

1. A modem card, comprising:

a connector configured to be connected to a computer;

electronics configured to be powered by power supplied from a power supply located in the computer; and

the electronics being configured to

transmit wireless signals to a communications network, the signals being transmitted at a transmit power,

vary the transmit power such that the transmit power does not exceed a maximum transmit power, the transmit power being varied such that a voltage of the power drops in response to increases in the transmit power,

determine a value for an adjusted maximum transmit power, the adjusted maximum transmit power being a transmit power at which the signals can be transmitted to the communications system without the voltage dropping below a shut-down voltage,

reduce a value of the maximum transmit power to a value that that is less than or equal to the value determined for the adjusted maximum transmit power.

2. The card of claim 1 , wherein determining the adjusted maximum transmit power includes:

increasing the transmit power to a revised transmit power where the power falls below a voltage threshold, the voltage threshold being equal to or greater than the shut-down voltage, and the revised transmit power being less than the maximum transmit power;

repeatedly reducing the revised transmit power and transmitting the wireless signals to the communications system using the revised transmit powers,

determining the voltage that results from each revised transmit power, and

treating one of the revised transmit powers that result in a voltage that is at least equal to the voltage threshold as the adjusted maximum transmit power.

3. The card of claim 1 , wherein determining the adjusted maximum transmit power includes:

increasing the transmit power to a revised transmit power;

transmitting the wireless signals at the revised transmit power;

determining the voltage that results from transmitting the wireless signals at the revised transmit power; and

determining whether the determined voltage is below a voltage threshold that is at least equal to the shut-down voltage.

4. The card of claim 3 , wherein determining the adjusted maximum transmit power includes:

decreasing the revised transmit power in response to determining that the determined voltage is below the voltage threshold.

5. The card of claim 3 , wherein determining the adjusted maximum transmit power includes:

treating the revised transmit powers as the adjusted maximum transmit power in response to determining that the determined voltage is at least equal to the voltage threshold.

6. The card of claim 3 , wherein

the electronics are configured to receive signals from the communications network; and

increasing the transmit power to a revised transmit power is performed in response to the electronics receiving a signal from the communications network which requests that the electronics increase the transmit power.

7. The card of claim 3 , wherein the voltage threshold is equal to the shut-down voltage.

8. The card of claim 3 , wherein the voltage threshold is greater than the shut-down voltage.

9. The card of claim 1 , wherein a set maximum transmit power is stored in the electronics and is not calculated by the electronics but is used as the maximum transmit power at some time during operation of the card, the adjusted maximum transmit power being determined to have a value that is different from a value of the set maximum transmit power.

10. A computer system, comprising:

a computer having a power supply that provides power having a voltage; and

a modem card removably connected to the computer, the modem card including

electronics powered by the power from the power supply,

the electronics being configured to

transmit wireless signals to a communications network, the signals being transmitted at a transmit power,

vary the transmit power such that the transmit power does not exceed a maximum transmit power, increases in the transmit power causing a drop in the voltage of the power,

determine a value for an adjusted maximum transmit power, the adjusted maximum transmit power being a transmit power at which the signals can be transmitted to the communications system without the voltage dropping below a shut-down voltage,

reduce a value of the maximum transmit power to a value that that is less than or equal to the value for the adjusted maximum transmit power.

11. The system of claim 10 , wherein determining the adjusted maximum transmit power includes:

increasing the transmit power to a revised transmit power where the power falls below a voltage threshold, the voltage threshold being equal to or greater than the shut-down voltage, and the revised transmit power being less than the maximum transmit power;

repeatedly reducing the revised transmit power and transmitting the wireless signals to the communications system using the revised transmit powers,

determining the voltage that results from each revised transmit power, and

treating one of the revised transmit powers that result in a voltage that is at least equal to the voltage threshold as the adjusted maximum transmit power.

12. The system of claim 10 , wherein determining the adjusted maximum transmit power includes:

increasing the transmit power to a revised transmit power;

transmitting the wireless signals at the revised transmit power;

determining the voltage that results from transmitting the wireless signals at the revised transmit power; and

determining whether the determined voltage is below a voltage threshold that is at least equal to the shut-down voltage.

13. The system of claim 12 , wherein determining the adjusted maximum transmit power includes:

decreasing the revised transmit power in response to determining that the determined voltage is below the voltage threshold.

14. The system of claim 12 , wherein determining the adjusted maximum transmit power includes:

treating the revised transmit powers as the adjusted maximum transmit power in response to determining that the determined voltage is at least equal to the voltage threshold.

15. A method of operating a modem card, comprising:

transmitting wireless signals to a communications network, the signals being transmitted at a transmit power;

varying the transmit power such that the transmit power does not exceed a maximum transmit power, the transmit power being varied such that a voltage of the power drops in response to increases in the transmit power;

determining an adjusted maximum transmit power, the adjusted maximum transmit power being a transmit power at which the signals can be transmitted to the communications system without the voltage dropping below a shut-down voltage; and

changing a value of the maximum transmit power to the value of the adjusted maximum transmit power.

16. The method of claim 15 , wherein determining the adjusted maximum transmit power includes:

increasing the transmit power to a revised transmit power where the power falls below a voltage threshold, the voltage threshold being equal to or greater than the shut-down voltage, and the revised transmit power being less than the maximum transmit power;

repeatedly reducing the revised transmit power and transmitting the wireless signals to the communications system using the revised transmit powers;

determining the voltage that results from each revised transmit power; and

treating one of the revised transmit powers that result in a voltage that is at least equal to the voltage threshold as the adjusted maximum transmit power.

17. The method of claim 15 , wherein determining the adjusted maximum transmit power includes:

increasing the transmit power to a revised transmit power;

transmitting the wireless signals at the revised transmit power;

determining the voltage that results from transmitting the wireless signals at the revised transmit power; and

determining whether the determined voltage is below a voltage threshold that is at least equal to the shut-down voltage.

18. The method of claim 17 , wherein determining the adjusted maximum transmit power includes decreasing the revised transmit power in response to determining that the determined voltage is below the voltage threshold.

19. The method of claim 17 , wherein determining the adjusted maximum transmit power includes treating the revised transmit powers as the adjusted maximum transmit power in response to determining that the determined voltage is at least equal to the voltage threshold.

20. A program product for a modem card, the program product comprising:

computer-executable logic contained on a computer-readable medium and configured for causing the following computer-executed operations to occur:

transmitting wireless signals to a communications network, the signals being transmitted at a transmit power;

varying the transmit power such that the transmit power does not exceed a maximum transmit power, the transmit power being varied such that a voltage of the power drops in response to increases in the transmit power;

determining an adjusted maximum transmit power, the adjusted maximum transmit power being a transmit power at which the signals can be transmitted to the communications system without the voltage dropping below a shut-down voltage; and

changing a value of the maximum transmit power to the value of the adjusted maximum transmit power.