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Loop the loop on 6 meters
Question T3C07 in the Technician Class question pool reads:
What band is best suited for communicating via meteor scatter?
- 33 centimeters
- 6 meters
- 2 meters
- 70 centimeters
The answer, of course, is B. 6 meters.
I make a big deal out of this question when I teach my one-day Tech classes because I think meteor scatter is probably one of the coolest things that Techs can do. Have I ever done it? Well, no, at least not yet.
Two months ago, I came across this video:
I also had a bunch of 75Ξ© coax that was installed back in 1985 when the house was built to distribute cable TV to the living room, bedroom, etc. Iβve never had cable TV in the nearly 25 years Iβve lived here, so I just cut a length from one of the cable runs. So, not only did the antenna look easy to build, I wouldnβt have to spend a dime on it.
Today, I finally got around to putting it all together. As you can see from the photo below, I used the military surplus fiberglass mast to get it up off the ground.
The photo below shows how I connect the loopΒ to the matching stub using a terminal strip.
Troubleshooting the antenna
When I first connected my antenna analyzer to the antenna, I was a little dismayed that the SWR was 14:1! I hadnβt expected it to be perfect, but I did expect it to be a lot lower than that.
The first thing I did was make sure that the wires were connected to the terminal strips properly. When that proved not to be the problem, I thought that maybe it was too close to my other antennas, so I moved it to the other side of the yard. That didnβt change a thing, either.
My next guess was that perhaps the coax was bad somehow, so I disconnected the matching stub and measured the SWR again. At 50.1 MHz, the SWR was now a much better 1.76:1. Since the feed point impedance of just the loop is supposed to be about 100Ξ©, I knew the problem was the matching stub.
In another video, Iβd seen the coax used for the matching stub coiled around a PVC pipe. The theory behind this is that not only the stub matching impedances, but also acting as a choke. I didnβt have any PVC pipe big enough, so I simply coiled the 75Ξ© coax and taped it together. WRONG! When I uncoiled the matching stub, the SWR came down dramatically, measuring about 1.1:1 at 52 MHz. Down at the bottom of the band, where I planned on playing, it was a bit higher, but it was still less than 1.5:1, and that is easily handled by my IC-7610βs antenna tuner.
Of course, now that I have the antenna, the band is just dead. Iβve been monitoring for the last hour or so, with nary a signal received. Thatβs just how it goes with 6 meters, I guess.
Meteor scatter here I come
I think that to be more successful on 6 meters, Iβll need to make some improvements to the antenna. For example, Iβll have to figure out a way to make the connections more robust and maybe add a little wire to the loop to bring the resonant frequency down a little. I probably should get the antenna up a little higher, too.
Building this antenna has been fun, and even though I stillΒ havenβt made any contacts, Iβm looking forward to operating 6 meters in the future. Maybe Iβll even get lucky and make some meteor scatter contacts. Then, when I cover that question in class, I can say that Iβve operated meteor scatter and itβs pretty cool.
