Friday, April 5, 2013

HAM issues

I am studying to upgrade my HAM radio ticket from a Technician class to a General Class. One thing I want to do when I get the new ticket is buy an HF radio. I am wanting to get into the 20 meter band, so I next have to see what sort of antenna I can get in there.

The lot is 77 feet wide, and the house is 52 feet wide. I need to figure out an antenna that will fit nicely and be hidden behind the house, or perhaps something that looks like a TV antenna, so I don't run the risk of neighbors running to the HOA and complaining.


Wayne Conrad said...

Cool! Does this mean Morse code in your future?

If your rig has a really good auto-tuner, you can make a good-enough antenna out of just about anything. Over at dad's house, we shot a messenger string over a palm tree and used it to pull up magnet wire. You can't see it, no way, no how.

At my house, it's plain old stranded wire, maybe 20 gauge, slung over a tree. The tree is on one end of the house; the shack is on another. The wire slants down from the tree, over the long axis of the house, until it gets to the side the shack is on, where it goes to a short pole I raised from the gable on the shack end. From the pole, it bounces off another short pole (not visible from the street) and through a small hole in the wall until it gets to my rig.

You can see the pole easily. The wire, you gotta be kinda close to see it.

Both work great. I worked Argentina on 15W with that antenna.

Both antenna systems are served by multiple wires laying on the ground. Unlike the antenna, which is pretty much random length, those wires are tuned to... if I recall... 1/4 wavelength of each band I operate on. A Really Smart Ham told me to do that, and it seems to work, but I lack the knowledge to know why it does.

Yay for auto tuners!

Since you've got an HOA, I'd consider magnet wire and see how that goes.

73, Wayne KF7QGA

Wayne Conrad said...

Things I forgot to mention, in the way of full disclosure:

* Since I have essentially no feed line, my antenna goes right up to the rig. The way I understand it, an end-fed antenna has humongous voltages on the near end. As a result, I have much RFI in the shack, and touching anything near my rig that's metal while transmitting can give me an RF burn. Having no feed line is not an essential characteristic of end-fed antennas. It's just a characteristic of me being very lazy.

* You wanna get advice from someone who knows something, not me :) I mentioned my (and my dad's) antenna to show that no or low visibility antennas can be done. They can be quite cheap and dirty and work pretty well.

SiGraybeard said...


That's a big one, giving privileges on all bands. I've had a great deal of fun with ham radio over the years. Like everyone, I drift away from it for a while, hardly operating at all, then go back and spend lots of spare time in the shack.

Let me know if I can help with anything. Been a ham since 1976, and have operated on every band from 160m up to 1296 MHz. Plus, I do design radios for a living, so that tends to help.

SiGraybeard said...

The biggest consideration for your antenna should be what you want it to do.

If you want to talk over local distances, out to a hundred miles or so, look into NVIS - Near-Vertical Incidence Skywave. A very fancy term for a horizontal dipole a few inches above ground. I seem to recall reading of guys actually laying it in the grass with pieces of wood to hold it down stretched out straight. The ground forces your pattern up, and the ionosphere returns it down around you, more or less circularly.

If you're interested in trans-continental or transoceanic distances, you want a lower angle of radiation, obtained by putting the antenna higher. Dipoles don't have to be straight and parallel to the ground.

In the past, and if I'm ever limited to a single simple antenna again, I'd put up an off-center fed inverted Vee. These are sometimes called Windom antennas, but there's a dozen or more variations - which is another way of saying it's just not that important how you make it.

For years, I've had a 40m off-center fed antenna up, fed about halfway out on one side. If a 40m dipole is 66 feet long, instead of feeding it at 33 feet (center) I fed it at about 16 feet from one end, and the other side was the rest of the 66'. The feed was coax to a 4:1 balun mounted by a screw eye to a cheap TV antenna mast, not more than 15' tall. (Making the feed off-center unbalances the antenna and makes currents on the coax braid - the baluns suppress the coax shield currents).

Using the built-in tuners in relatively modern HF radios (Icom746 and up) I was able to tune that antenna from 40 to 6 meters(!) and I'm sure I've worked DXCC on at least 40, 20 and 15 with it. The relatively cheap autotuners (LDG or MFJ or ??) would tune a much wider range of impedances, so the starting antenna doesn't even have to be as good as the 40m dipole!

Hope that's useful...