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IOTA 2010 – Cape Lookout Expedition

Operating under special event call N4A, for the fourth year we once again activated the South Core Banks from Cape lookout a few miles up the beach from the CALO lighthouse. Fun facts and photo strip on the N4A operation on its web site. Additional photos on flickr. Also a short youtube clip of N4YDU running them on 20m SSB.

An operation on the beach as an expedition is always a great chance to learn new stuff. This year we learned that fiberglass mast is pretty flimsy and aluminum is much stronger – not a revelation.

After some extensive modeling by K2AV, we settled on using ladder line fed doublets that were 56 feet(17.2m) in total length, 28 ft per side. The models show that length to have useful lobes on 15m and 20m, without loosing much over a regular 40m dipole. We ran the ladder line to just behind the radio’s into 4:1 baluns, and used the radio internal tuners for matching. [I’d have preferred outboard tuners.]

We didn’t get good enough propagation on 15m to decide if they were making a difference, but two of these antennas at right angles, with their apex at 40 feet, seemed to work very well on 40m and 20m. On 20m, there was a worthwhile difference between the two antennas, several s-units in many cases. The signal level difference on 40m was more subtle. The pattern on 40m at only 40 ft high is mostly omnidirectional anyway.

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