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Electronics

Saltwater Cellular Page 2

Electronics - September 2001
Electronics September 2001
By Ben Ellison


Saltwater Cellular
Part 2
   
 



 More of this Feature

• Part 1: Saltwater Cellular
• Part 2: Saltwater Cellular continued

• Currents

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• Electronics Index

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• BoatAntenna.com
• Digital Antenna
• Shakepeare Marine

 

Some boaters have stuck to analog service. The coverage in North America is good, there are still portable and fixed full-wattage phones available, and it's fairly easy to hook one to an external antenna. However, if you want the flexibility of a pocket phone and/or the lower rates and greater features of digital service, you may need some accessories and some knowledge of the confusing array of acronyms that constitute what's known as second-generation (2G) wireless.

First-generation cellular was analog, with a single service using a single band (800 MHz) and a single interface (AMPS). 2G is all digital but uses several often-incompatible combinations of services, bands, and interfaces. The first systems--simply called Digital Cellular--work the same 800-MHz band as analog, and the phones have the same maximum 3-watt output. Newer PCS (Personal Communications Service) and GSM (Global System for Mobile communications) digital services usually operate on the 1900-MHz band, with an FCC mandated maximum 2-watt output. Two different channel-sharing interfaces--TDMA and CDMA--add to the alphabet soup, and then there's Nextel's unique iDEN system and the variations of GSM in use outside North America. What's a guy to do?

Certainly dual- and trimode phones make sense for boaters. If your primary digital service can't connect, these phones may then roam to another digital (or analog) mode that can. By the same token, if you install an external antenna for your handheld, it's wise to get one tuned for both cellular bands, enabling multimode flexibility now or in the future.

External antennas--even a simple car whip--make a difference, though there is disagreement about the ideal design for a marine unit. Antennas produce gain, measured in decibels, by focusing the transmission signal onto the horizontal plane, and there's a lot more to their design than one might think. According to in-house testing cited by Shakespeare Marine's marketing director Don Henry, flattening a cellular signal beyond 3 decibels tends to cause fade-outs as a boat rolls; hence, Shakespeare's antennas are all 3 decibels. Digital Antenna president Bud Gallagher claims to have engineered this problem away, and his units are all 9 decibels. Both companies offer dual-band models in different lengths with various mounts. Note that since the antenna's internal element is short, a taller antenna increases height (which is good) but not gain (as in VHF antennas).

Cabling is a real issue with external cell antennas. Good connections and low-loss wire are essential to getting the wimpy output of a 0.6-watt portable to the antenna intact. Digital Antenna and Shakespeare both supply premium quality RG-8X leads, and Shakespeare will soon introduce its own proprietary version. You also need a short adapter cable to make the connection between the phone and the antenna wire, and since there is no standard antenna plug, these are only available for some phone models.

BoatAntenna.com carries a variety of such interconnects as well as a power booster that is the next level in the quest for cellular range. Company founder Howard Melamed says that boosters for digital handhelds are just coming to the market, as the range problems I've described manifest themselves. His present model will bring a handheld's 800-MHz analog and digital power to 3 watts. Another model soon to be introduced by Digital Antenna will also increase 1900-MHz service to its 2-watt maximum.

Howard reports that some of his customers are making calls an amazing 50 miles offshore using a booster combined with a good external antenna. They've beaten the decreasing range trend plaguing marine cellular performance, while retaining the advantages of pocket phones and digital service. Meanwhile, companies like Garmin, Raytheon, and startup Onboard Wireless have all recently introduced interesting products that address other marine cellular issues, which I will discuss next month.                                  

BoatAntenna.com Phone: (877) 998-BOAT. Fax: (954) 340-9086. www.boatantenna.com.
Digital Antenna Phone: (954) 747-7022. Fax: (954) 747-7088. www.digitalantenna.com.
Shakespeare Marine Phone: (800) 800-9008. Fax: (803) 276-8940. www.shakespeare-marine.com.

Next page > Currents > Page 1, 2, 3

This article originally appeared in the June 2003 issue of Power & Motoryacht magazine.

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