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coax on the Stick Trail
Sunday, July 5 2009
I'd bought 500 feet of 75 ohm coax cable the other day as one of the supplies need to attempt an experiment. The goal was to increase the range of the household Panasonic KX-TG1033S DECT 6.0 phone system, which barely reaches the greenhouse. I wondered if I could route the antenna signal from the base station down a cable and broadcast it from a remote antenna, perhaps one mounted on the solar deck. The base station has two antennas, so I could just clip one off and attach the core of the coax to the stump, allowing the other antenna to continue to function.
Today I unspooled all five hundred feet of coax, starting in the laboratory, going through the teevee room, down the stairs, across the living room, out the sliding doors to the south deck, down the steps to the Stick Trail, and then south down the Stick Trail to within 100 feet of the Chamomile "River." This was well beyond the range in which our phone handsets remain functional, so all I had to do was attach a little 3.1 inch wire (half the wavelength of the 1.9 GHz signal) to the remote end of the coax, attach the other end of the coax to the antenna stump of the base station, and ground the coax shielding.
One thing I didn't expect was the electrical shock I experienced when I grabbed the coax shielding while standing barefoot in the muddy Stick Trail. The base station was powered by a wall wart, but that was isolated from the truly-grounded high-voltage world of alternating current. Why, then was there such a large voltage differential between the coax shielding and the actual ground? I measured this differential with a multimeter and it was about sixty volts. I tried attaching the shield on the remote end of the coax to a wire stuck in the mud, but this introduced an unwanted hum to the phone reception experiments that this was really all about.
I was able to get the handset to function near the remote end of the coax, demonstrating that I could send the 1.9 GHz signal down 500 feet of television cable. But the signal had been severely attenuated and I couldn't go more than ten feet from the remote "antenna" before the handset reported that it had lost its connection. Still, this demonstrated that the signal could be sent down a cable, and in the application I envisioned, the signal would only have to go down 100 feet of cable.
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