AA8IA Amateur Radio

Antenna for HF – What to do?

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I haven’t ruled out a vertical antenna. A vertical is doable. I’d sure make use of it from the standpoint of DX. But, in the meantime I’d really like to put up a dipole that will perform as best as it can possibly perform.

This means I have to get it up in the air and in the clear of as much as possible. That way it has a good pattern and is able to hear something. Keep in mind, I’ve had dipoles up at various times since 1991. But during all of that time, I didn’t care whether it performed as well as it could… as long as I was making contacts. But now i do care.

If you can picture an inverted-V dipole that lost its middle support and fell down exactly 90 degrees from vertical, that is what my current antenna looks like. It’s a horizontal V, with the center supported at 12′, one leg sloping down the end of the yard at a 45 degree angle and anchored near a fencepost and the other leg sloping upwards at a 45 degree angle in the opposing direction anchored about 25 feet up in a tree.

There can be no predictable pattern; there can be no gain; and the performance is mediocre at best.

So, I want to get a dipole up for 40 through 10. I don’t have 35 foot anchor points for two ends of a 40m dipole, so I have to go with an inverted V and a push-up mast.

To add insult to injury, if I expect it to tune up and have any efficience at all it needs to be fed with ladderline. I’ve never tried to run ladderline into the house and find that it’s not going to be easy to do while isolating the ladderline from nearby objects that might affect it. If I feed it with coax, I potentially can get it to tune on more than one band — but that doesn’ tmean it is efficient. I’ve read a lot about dipoles and what happens when it has a significantly high SWR at the antenna feedpoint and you then tune out that high SWR at the end of the feedline. You end up with a situation where most of your signal is lost between your transmitter and the antenna, depending on the band.

Then there is the issue where a 40m dipole on 10m just isnt’ going to have the pattern I would want on 10m.

I’m thinking that if I get a dipole up in the air, I might construct what some call a fan dipole. Now, we won’t debate the name — although I’ll say that technically what I’m referring to likely isn’t a fan dipole. One feedpoint, two or three sets of wires of differing lengths for the separate bands that I want to have available. A 40m dipole should cover 40m and 15m (7 mhz and 21 mhz) with 21mhz being the third harmonic. then add a another site of wires at the same feedpoint for 20m and another set of wires for 10m, with each set of wires spaced far enough apart from each other so that they do not have appreciable effect on one another. I’m thinking this would likely give me a good performing setup for 40m / 20m / 15m / 10m and I could potentially work 17m / 12m somewhat inefficiently.. but maybe not.

Ok I’m just thinking out loud. at any rate, I really want to get a dipole up. I’d get a push-up mast, probably a 35 foot pushup mast. I’d use a 90 degree angle on the V.

The needed minimum height on a 40m inverted V with a 90 degree angle is 21 feet. However, one would want to have it a little higher so that the ends of the V could be a few feet off the ground. A 35 foot push-up mast should do the trick nicely and allow the ends of the dipole to be up off the ground a significant distance and out of the way of humans/animals.

Then another problem arises. if you are using a push-up mast, at least in my area, you must guy it. Guying is a pain in the ass. Suddenly that inconspicuous dipole that you erected isn’t so inconspicuous when you have to have guy wires flailing around all over the place.

I want a dipole, regardless of whether I have a vertical or not. A vertical’s takeoff angle is going to be one that favors DX, and there is a lot of the US that I would like to work as well. Plus, a dipole as a general rule is going to be quieter, since a vertical is more susceptible to manmade noise. It’s only logical for an amateur radio operator to have at least one dipole in his/her arsenal, regardless of whether they have a couple of 100 foot towers with stacked arrays on them covering the bands or a nice vertical.

There are more opinions about the best antennas to have around than there are assholes, and a lot of those opinions come from assholes. But, there also are a lot of knowledgeable people out there who are willing to share their thoughts and offer some assistance. The QRZ forums have a handful of such guys. I’ve been reading a lot written by these guys. This is what is causing me so much delay in getting any antenna at all up.

I want to get some antennas up for HF that in total are cost effective, that aren’t complete eyesores to the neighbors, that will weather the high winds here, and that will fit into the limited space that i have available (65′ x 100′).

Written by Mike

May 13th, 2010 at 3:16 pm

Posted in Antennas

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