Cellphones

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The Hummer Knowledge Base

Accessories/Communications/Cellphones:

As an RF Systems Engineer, I am often asked by fellow HUMMER owners what is the best form of long distance communications, "... in case `the worst' happens". It seems that with the HUMMER's unique off-road prowess, people are venturing way beyond the coverage areas of today's cellular markets. While there are many exotic solutions ranging from HF maritime gear to Satellite communications, I had an opportunity to try out a simple, cost effective solution on the HOA Nevada trip this past week.

The concept is based upon extending the existing cellular coverage way beyond specifications. Cellular coverage areas are defined by usability criteria, which usually includes a modern cellular tranceiver coupled to a glass mount antenna with 18 feet of coax cable in between. This configuration is considered usable when a call can be placed and completed while driving without being dropped. To extend range, we must modify our criteria for "acceptability". If we assume the vehicle is stationary, we immediately realize a substantially larger service area.

Once stationary, the glass mount antenna is replaced with a high gain, commercial quality directional antenna. These antennas should not be confused with the inferior antennas sold through catalogs as "range extenders". Mail-order antennas are as usefull as the "250,000 lb. rolling weight winch with cigarette lighter plug" that appears on the facing page in the catalog. Commercial antennas are constructed of welded aluminum, tuned to length, and fitted with a Type-N female connecter. They can be purchased for under $100 through commercial two-way radio shops. Most shops can also make a short length of cable to go from the Type-N connector on the antenna to the SMA or mini-UHF connector on the cellular phone. Keeping this cable short greatly reduces the signal loss in the cable.

Once attached, the antenna is slowly rotated by hand while watching the signal strength display on the phone. From my location, somewhere in the Nevada desert, my phone was showing "No Service" after parking. By attaching the directional antenna, I received a 4/6 scale S reading and "Roam" indicator on the phone. It turned out I had accessed the Bishop, CA system over 65 miles away from our location (as verified by my GPS). Pointing the antenna more east, I was able to access a Nevada cellular system. The 611 operators were stunned, but quite helpful when I asked them where I was.

This solution works well if you're within 150 miles of a cellular system. It works best with mobile, transportable, or "Bag" phones. Since you're using your exsiting phone and service agreement, it carries no additional monthly costs. The antenna I used was 6" tall and about 22" long, weighing about a pound -- an easy carry along item in my HUMMER wagon. Although you can not drive off with the directional antenna attached, it does provide reliable communications for a low cost.

Everett Fred Basham

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