Restricted area multi-band HF antenna

[Alfdude1]

I live in a condo and recently upgraded to General. I would like to start using the HF privileges I just earned, but need some antenna advice. I would like to cram as many frequencies into a single antenna as possible, but do realize that it will work well on some frequencies and not so well on others. I need some advice as to what type antenna to look at. I have heard about loop and folded dipoles, magnetic loops, fan dipoles and verticals just to mention a few. I am going to have to mount this in the attic so space is limited. The attic measures 39' long and 15' wide across the floor with a 9' peak (from the floor). I already have the 2m and 440 taken care of so I am looking for 6m on up (as many as I can cover somewhat efficiently). I have photos of the attic available if needed.

Thanks in advance,
Mike KA6ALF(formerly KD6NVO)

 

[k9rzz]

I'm going to come across as the wise guy again, but it sounds like you've already done some research on the matter .... pick one and try it! No? Try a different one. Leave the first one up and add a second one, compare. (okay, that's my 5th edit. I'm done.)

 

[k9rzz]

Oh, and welcome to Radioreference. Not everyone is as rough as me.

 

[popnokick]

Forget the vertical... Needs extensive ground plane system and you don't have room in the attic. (And that guarantees someone will suggest a vertical.)
There are various longwire, dipole, and loop antennas you can try. But get a good tuner. (And writing that guarantees someone will suggest you don't need a tuner.)

 

[mrweather]

There are vertical dipoles that don't need ground radials (I'm using a Cushcraft MA5V right now) but yeah they would be way too tall to fit in an attic regardless.

 

[Alfdude1]

Thanks for the input. I would love to have all kinds of money to keep buying antennas just to try them out, but that won't happen. I did not do very much research, as I was looking for real world experience. I looked into the Maldol HVU-8 if I can get approval to mount it outdoors.

 

[prcguy]

Hey, not so fast...He does have room in the attic for a vertical in the form of a large screwdriver antenna like a Tarheel 100, 300 or other similar brands. I run a Tarheel 100HP on my truck and it kicks butt and several friends run large screwdrivers on their condo balconies and put out a surprisingly good signal, even on 40 and 80m.

You can line the attic floor with cheap chicken wire as a ground plane and that along with the attic being elevated will probably work better than the same antenna on a vehicle. You can also replace the top whip with a wire just long enough to reach the rafters, then branch a few wires out sideways as a capacity hat.

If your not interested in 10 or 15m you can make a huge capacity hat stapled to the rafters that would be the equivalent of a 20+ft whip on top of the coil which really improves efficiency on lower bands. This all depends on the roof material being fairly transparent at HF. Hanging a dipole in the attic can work but 39ft of linear space limits you to the upper bands or you would have to get creative with loading the dipole elements.

Then there is the problem of electrical wiring that typically runs through attics and that would be in very close proximity of a horizontal dipole. The mobile screwdriver gets around this being vertical and hopefully all the electrical wiring would be under the chicken wire ground plane where it would have little effect on the antenna. Plus you would not need a tuner with a good screwdriver, as popnokick predicted would be mentioned.
prcguy

Forget the vertical... Needs extensive ground plane system and you don't have room in the attic. (And that guarantees someone will suggest a vertical.)
There are various longwire, dipole, and loop antennas you can try. But get a good tuner. (And writing that guarantees someone will suggest you don't need a tuner.)

 

[k9rzz]

It doesn't take hardly any money to experiment with antennas. Get your OWN real world experience and build your own. It's not hard and you'll learn as you go.

 

[nanZor]

The attic measures 39' long and 15' wide across the floor with a 9' peak (from the floor).

In many cases for me, that would have been a total luxury!

My first inclination would be to simply run an inverted-L, with basically a 9-foot vertical, with a 39" horizontal flattop. Spaced a few inches away from the rafters. Underneath, a single 39-foot "counterpoise". Use a tuner, BUT try to tame the common mode from the coax with a nice RF-Choke / Isolation balun near the feedpoint. 6 turns of coax doesn't cut it. Use good quality coax, not bargain-basement RG-58.

Balun-Designs makes some very nice ones.

You could also try treating the whole setup as a non-resonant inverted L. In this case, you would use a 1:1 UNUN, followed by a good RF-choke isolation choke. A remote tuner in the attic would be nice, but might be impractical. Here, the losses of having the tuner in the shack might be acceptable.

Since this is a compromise environment, I wouldn't worry too much about radiation angles until you just try it.

I'm also with Prcguy on the ease of building a top-loaded vertical, where you could run some wire at the top - ie a "T" loaded antenna for total simplicity. You also appear to have room for at least four, 15-foot radials (or 2 minimum) if you were to place this vertical in the center of the attic.

With some slight tweaking, you could monoband it for 20 meters, or use the additional loss from a 1:1 UNUN / shack tuner setup to at least be able to tune multiple bands. (also USE the choke!)

Just some ideas to whet your whistle.

 

[vagrant]

I vote for a loop antenna, or a screwdriver vertical.

 

[AC2OY]

Every guy in my club that had one of those tar heel on the back of their trucks can operate on many HF bands. I have another guy how is going to buy one for his condo!!!

 

[zz0468]

I'd put up a doublet, and open-wire feed it from an autotuner. Multiband, no ground connection required, no radiation from the coax into the house.

An autotuner feeding a loop run around the attic would be just as easy and effective, maybe more so.