Sunday, January 1, 2012

Got a Rig, Got an Antenna

I've got an HF rig for amateur radio now. I've been trying to figure out how to get started since working with the VHF equipment I already have on hand hasn't been working out well for me so far. Based on what I picked up on my short wave radio it looked like the high frequency bands should do well here where I live.

Last week I got a used Kenwood TS-450SAT. It's a really nice older rig, the set-up I bought included the antenna tuner (thus the "AT" in the model number) and a good power supply (Astron RS-35M). It's capable of 100W out on all the HF bands (less in AM, 40W if I recall correctly.)

Next I needed an antenna.

Two days ago I fashioned up a quickie dipole out of some 3/8" cable shielding I had on hand. It was the end of a spool, I had about 80 feet. I cut two pieces about 35 feet long to make a dipole about 67 feet long overall once all was said and done. My time was short, I soldered some 12 guage solid wire on to an SO-239 bulkhead connector, soldered that to ends of each piece of braid, put loops in the 12 guage and tied a piece of rope between them as strain relief, then make a couple of end insulators out of short chunks of PVC pipe.

More 12ga solid wire went into the outer ends of the PVC insulators to finish the antenna's first incarnation.

The light was already failing, but I managed to go outside and run the antenna from a manzanita bush on a hill next to my home, about 20 feet higher than my roof. The other end went to an old bicycle inner tube looped around one of the vents on my roof. A poor installation, but all I had time for as it was about full dark by the time I came back inside.

A sixty foot piece of RG-8 with PL-259s on the ends ran from the center connector, through a cracked window, to my rig. I stuffed the crack with ratty garage towels.

My MFJ-259B reported that the SWR was out of bounds on 160m, good on the high end of 80m, so-so across 40m, worse on 20 and 17m, good in 15m band, decent in 12m, and barely usable in 10m. What the heck. I hooked it up to the TS-450S.

I didn't know if I was going to try sending anything when I hooked it up, but once I got started I realized I had my hands full just figuring out how to listen on my new rig for the first evening. I managed to listen in on a net on 40 meters and hear a few QSOs. The antenna brought in more than I get with the whip on my short wave radio (whew!), but is still wasn't all that great.

I'd noticed that the MFJ-259B said that the best frequencies on my antenna were all just above or at the high end of the ham bands I most expected it to perform at.

So yesterday I went out with my ham daughter (KJ6TFT) and we did a re-do on the antenna. I shortened it up a bit (between stretching and poor quality control in the initial build it measured out as a bit over 68 feet), did some mechanical touch-up, and installed it in a better location.

I was limited by the length of my RG-8 feeder line, the only one to my name at present as another length of Belden duo-foil cable turned out to have a kink in it where the center conductor pushed through the inner insulation to touch the shield. So we ran around the steep end of my property with a 100' tape measure for a while and came up with an idea we hoped would work.

We picked an oak tree at about the right distance at the top of the property (still below the hilltop, which my neighbor owns) to attach a 12 foot board with one end of the antenna. The antenna then slopes down to another 12 foot board with a 2x3 reinforcing board that's attached to the edge of my garage roof and the garage wall through a T. We were planning to use nails at some points, but went to screws when it became apparent during the hand-held test-fit that tension was going to be a lot higher than we originally thought.

How is it that antennas weigh ten times as much in the air as when you carry them in your hands? ;)

We spent almost the full day working out the niggling details of this "temporary" antenna installation. Besides getting on the air quick, this antenna is also intended to give me some idea of what I can expect to catch off the air here, let me know how the orientation it's at will work (it's north-south), and otherwise just give me some practical experience before I start any elaborate plans for a permanent antenna.

I learned a lot before I even got to the point of hooking it back up to my rig. Which is good. I can see several mistakes I would have made if I'd tried to dive into a permanent antenna design right off the bat. I've heard it said that a quick and dirty antenna takes just as much work as a full-fledged proper job, so why bother with the quick and dirty at all? In my case I can say that by using available materials and not expecting too much I've managed to learn a lot that will make the "real" antenna a much better antenna than it would have been otherwise, and I'll have a much better idea of what to expect without making too many guesses.

Once hooked back up to the rig, the extra altitude of the new installation showed its effect. I was hearing a lot more across all bands. The difference was huge. When I later disconnected the cable and checked the antenna on the MFJ-259B the numbers looked only marginally better, but then an antenna analyzer doesn't evaluate the location of an antenna, except as it affects the antenna's electrical characteristics. At any rate, the SWR is better across most bands (some got just a little bit worse), but the real story is in the reception. Which is much improved.

So now I just need to do a little more reading in my transceiver's manual to make sure I have the least clue about what I'm doing when I hit the PTT button. So I'd better close out this post and get to it.

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