Cell phone communications system.

Project date: 2010

While the primary communications system for a boat is a VHF Marine system, a cell phone has a place for personal communications needs. In that frame, this should be considered an addition, rather than a replacement for a VHF radio.

The ideal Cellphone system would:
- Provide extended range.
- Keep the Cellphone safe, and allow it to be charged while on standby.
- Provide a good interface for the noisy environment while the boat is underway.

Here is a block diagram of the system:

RF Amplifier:

Depending on the technology your cellphone uses, a RF amp may or may not be available. Unless you have a Nextel or iDEN phone, Digital Antenna's DA4000 direct wired amplifier will probably work. This is the one I am using. Other options are a wireless amplifier such as Digital Antenna's DA4000MR wireless repeater. Since the wireless version is only available from Digital Antenna as a kit, I am covering the installation of the DA4000 in my boat.


The amplifier wiring is pretty straightforward, simply find an out-of-the-way place for the amp, then wire in power, antenna, and cell phone input. I put a switch on the amp power input so that I could turn it on or off as needed.



The amplifier comes with a 2ft cable to connect the cell phone to the amplifier. If you extend this length, please consult with Digital Antenna for the proper cable. Using the wrong cable may result in excessive signal loss, and you may not be able to transmit through the amplifier and antenna.

The antenna is a Digital Antenna 567-CW dual band 8ft cellular antenna, mounted to the Starboard side of the radar arch.


The input to the Cell amp and 12V for the Cell phone charger cord is mounted into a wall jack.

For best results, use a cell phone that has an antenna connection. Many different adapter cables are available for a host of different phones. If your phone does not have an antenna connection, a universal adapter is available that is essentially a small antenna that affixes to the phone.

When in port, where there is sufficient signal, I generally leave the amplifier disconnected and powered down. In this regard, you can consider the amplifier part of this project as optional.

Digital Antenna makes the claim that a 50 to 75 mile range is possible with the amplifier and external antenna. I suppose given sufficient antenna heights this may be possible. However, I can easily use this system 10 miles off shore with full signal strength, which is probably sufficient for most of us.

Audio Interface:

The number one problem with a cell phone, at least in a marine environment, is noise. Engine and wind noise make it all but impossible to use the phone under normal conditions. But there is a solution for that as well.

The upper mic device is a Cobra MR F300 BT handset. This device does not connect to a radio as it's shape suggests, but actually contains a Bluetooth interface to the cell phone. Most of the cell phone's functionality is available through the handset, including a phone book, mic, built in speaker, volume control, and a whole host of features. Also, and what is probably the most useful feature, an auxillary output is available so that you can connect the speaker to the stereo system.

The handset cord provides power to the handset as well as audio back to the stereo system.

The handset also has a noise cancellation feature, and I have used the handset in a 25mph (self made) wind on the flybridge with full quieting. Its an amazing feature, and makes this handset capable of clear, quiet conversations.

This control panel at the helm contains a switch and potentiometer.

The switch connects the handset's audio output to the boat's radar arch speakers, while the potentiometer is the amplifier's volume control.

Integration into the stereo system:

The switch functions as follows:

- In the down position, the arch amplifier is controlled by the on/off switch at the stereo system in the salon.
- In the up position, the arch amplifier is switched over to the Bluetooth headset regardless of whether the amp is connected to the stereo system or not.

For further information on the arch amplifier's integration into the stereo system, please review the following:

Integration into the boat's stereo system
Arch Stereo Amplifier Wiring

Additional Features:

The Cobra Bluetooth Mic has several other handy features, including Hailing through the stereo system (arch speakers), VOX (voice operated transmit) or PTT (Push To Talk) keying, selectable ring tones, call log, phone book, and its waterproof.


Rarely does a project exceed your expectations. However Cobra's Bluetooth Handset is an amazing device, and should be considered if you have a need for high-quality Cell phone conversations in a high noise enivornment. With the Cobra handset, there is no need for a cumbersome wired headset or bluetooth device stuck in your ear.


Cobra MR F300BT Waterproof Marine Handset
PowerMax DA4000, 3 Watt Dual Band Cellular Amplifier
Digital 567-CW 8' Cellular Antenna




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