POWERING A COMPUTER ONBOARD

Onboard WiFi Primer

WiFi operates at 2.4 Ghz with relatively weak transmit power. Two important facts to know about radio signals in this frequency range are that water and most solid objects absorb considerable amounts of any signal and long coaxial cable runs to antennas can reduce power output at the antenna by half or reduce the incoming signal strength to the point that the signal is not usable.

All onboard WiFi systems have a computer connected to a WiFi transceiver which is connected to an antenna.

The connection to the computer can be through a PCMCIA port, PCI port, mini-pci, USB port or LAN port. The first 3 connections are internal to the computer with the transceiver either totally within the computer or partially accessible to the user. A USB transceiver can be directly plugged in the computer or connected by an extension cord. The LAN connection uses CAT5 network cable to connect the transceiver to the computer.

The WiFi antenna can be either internal to the computer, USB device or PCMCIA card or it can be an external antenna which attaches directly to the transceiver housing or to the transceiver using coaxial cable.

The best system for onboard WiFi reception will use an antenna deployed so that it has a 360 degree view of its surroundings not blocked by any vessel structure other than the mast & rigging. The transceiver should be mounted as close to the antenna as possible to minimize or eliminate the coaxial cable run. The best types of transceivers to use to achieve these goals are ones that use USB cable or LAN cable to connect to the computer.

Any transceiver that can connect with an AP (access point) is operating as a "client device".

USB based adapters are the least expensive way to set up an onboard system. They can be placed up to 15 feet from the computer by using a passive extension cable. Additional extensions of 15 feet can be achieved using active extension cables. One computer can be used per adapter.

The client bridge provides the most flexible WiFi system. These adapters use POE (power over ethernet) which allows 1 CAT5 cable to carry both data and power. This allows for unrestricted placement of the adapter. A client bridge can provide input to an access point on the interior of the boat so that any wireless equipped computer onboard can access the internet. You end up with a network similar to what you may have used onshore except that the client bridge takes the place of the DSL or cable modem.

How Many Serial Ports Do I Need?

I use 3 com ports to run my navigation and communication software. One port takes the GPS nmea data, one port takes my Pactor Modem and one port controls the SSB.

USB ports are another type of serial port. Most types of peripheral equipment can be operated off of the USB ports. I keep an RF transceiver for a wheel mouse, a WIFI transceiver, an infrared dongle for internet over the cell phone and a printer plugged in all the time. In addition I use the USB ports for a floppy drive, external hard drive and power for an amplified pair of speakers. If you run MaxSea or Nobletec software you'll probably have a USB dongle with a software key plugged in all the time. You'll use as many ports as you have. You can never have too many ports.

I've just hooked up my GPS to my new PC and the mouse pointer goes crazy when I boot up the computer. What's going on?

If NMEA input is present on your com port when Microsoft XP starts up XP recognizes this input as a Serial Ballpoint Mouse and loads a driver for it. The following steps will cure the problem. IslandTime PC's are modified before shipment to prevent this problem on any of the COM ports.

1. With the GPS connected and running boot the computer.
2. After the machine is up and running regain control of the mouse pointer by turning off the GPS or otherwise removing the input signal.
3. Select START>CONTROL PANEL> SYSTEM>HARDWARE TAB>DEVICE MANAGER BUTTON>
4. Find "Mice and other Pointing Devices" and expand it.
5. There should be an entry for "Microsoft Serial BallPoint". Right click and select "Properties".
6. At the bottom of the Properties window there is a drop down list. Click the arrow to open this list and select "Do Not Use This Device (Disable)".
7. Click OK to close the window.
8. It's best to restart your computer immediately to save your changes.

IslandTime PC * 243 W. Orange Ave. * Wewahitchka, FL 32465 * USA