Fall 2007 Issue

The Lost Letters
of KH6UK


Part 2 – The VHF Moonbounce Years
(1958–1959)

 

In part 1 of this three-part series in the summer issue of CQ VHF, WA2VVA discussed how he came across the lost letters of Tommy Thomas, KH6UK, along with Tommy’s QSO with W6NLZ. Tommy’s story continues here in part 2 with a discussion of his efforts on EME.

 

By Mark Morrison,* WA2VVA

Photo A. KH6UK’s moonbounce antenna array in August 1958.


Tommy Thomas, KH6UK, once commented to Walt Morrison, W2CXY, that the inversion season in Hawaii was the same as on the east coast of the U.S., from July to September. Therefore, it was during the winter months that Tommy did the routine work of maintaining old antennas and making new ones.

Following the successful 144-MHz tropo season of 1957, John Chambers, W6NLZ, suggested to Tommy that he prepare for 220-MHz tests the following year. At the same time, other hams in W6-land—including W6PJA, W6AJF, K6QFI, W6DNG, and W6WSQ—were asking Tommy for schedules on 144 MHz. Tommy obliged both interests by building an array for 220 MHz and replacing his existing 144-MHz array with an even bigger one. This larger antenna would serve as Tommy’s entry into serious moonbounce tests.

Tommy had been thinking about moonbounce ever since landing on Hawaii. The only thing holding him back was his not knowing exactly what to build. Tommy would write many letters to other hams working on the “moondoggle,” as he called it, asking for test results of their various antenna designs. Jim Kmosko, W2NLY, and Herb Johnson, W6KQI, were testing Long John Yagis of unconventional element spacing. John, W5VWU, was pushing circularly polarized arrays. Walt, W2CXY, was testing Long John Yagis with more conventional parameters. Fran, W2OPQ, was evaluating UHF resonator colinears. And Ross Bateman, W4AO, one of the first amateurs to hear his own echoes off the moon in 1953, was using stacked rhombics. Whatever kind of antenna Tommy built would depend largely on the testing performed by these other amateurs. Not having time to experiment on his own, it was essential that Tommy listen to what they had to say.

From the very beginning, Tommy was concerned about having enough antenna gain for moon-reflection work. At first he considered 25 dB to be the minimum gain required. In a letter to W2CXY he put it this way:

The gain of 25 dB in the antenna as a requirement for a Moon Bounce signal may or may not be correct. The Amateurs have always done better than it was supposed possible.

Later, based upon what little information existed at the time, and the results of amateur testing where echoes had been heard, he conceded that 20 dB might be enough. Still, he used to wonder why some stations could hear their own echoes but not be heard by others, and why these same stations could only hear their echoes when the moon was low on the horizon. With the exception of Ross, W4AO, all such stations were using four Long Johns of one type or another, with gains on the order of 20 dB.

Tommy was also concerned about the high winds at his seaside location in Kahuku. When Tommy put up his first antenna for 144-MHz tropo testing, he placed it high up on a utility pole where it was subject to these high winds. Concerned that an even larger antenna might not survive the winds, Tommy took the advice of Walt, W2CXY, by placing his antenna close to the ground:
I think I agree the thing to do is to put up something fairly big on the stick and to build a big array like you plan—near the ground where you can tilt it and where it isn’t apt to blow down.

In the end, Tommy decided on a 2 ¥ 4 array of eight Long John antennas with two-wavelength spacing between each antenna. Such a large array would certainly address Tommy’s concerns about antenna gain, but brought new concerns about mechanical integrity.

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