Megan (jehoshabeath) wrote,

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Antenna construction

Yesterday: 6:30 am wake up
From 9am - 9pm work in the field (in this case, yard) on a 40 meter four-square antenna
Dinner: 9pm and then sleep at 11pm

The four-square is special because even though it is stationary it acts like a rotating antenna. You know how a lighthouse shines a beam of light through the sky? This kind of antenna is called a "beam antenna" because it sends our radio signal as a directed, concentrated beam through the air. And just as the lighthouse can move that beam of light around, we want to be able to move the signal in a different direction.

The antenna is composed of four poles that each reach over 30 feet high. They are guyed with rope and a pulley is attached to the top. The pulley is what hoisted our antenna wire to the top. This is the same for each pole. Then, the four are connected at the center to a control box, which can control the direction that the signal will be concentrated in. We had a network of radial wires and coax cables and the whole system was quite nice when it was all put together. It was tiring, but very satisfying.

We had a slight incident with our first pole. I don't think the guy wires were spaced well, and when we lost our concentration, the whole unit collapsed. No one was hurt, but it was a lesson learned. After that, we made sure to pay close attention, stay out of other people's way, and do only as we were directed by the caller. It is tricky to act as a guy wire. You simply cannot tell whether you need to apply tension or slack because, from your angle, all you see is the side-to-side motion of the pole. It requires a good spotter to call which guy needs to adjust tension and a good guy wire person to respond quickly without overdoing it. Our next four poles went up very smoothly and without incident by following those simple rules and a little spacing adjustment.

Today I go out again to finish with some things. It's the last day for antenna design and prep work, and I don't think there is a whole lot left. At least, there is nothing as complicated as what we built today.
Tags: radio equipment, radiosport

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