Building my very 1st antenna...for the attic

[DJMarkham]

TL;DR

Need to figure out the length for the ground plane and the top hat, based on the vertical element length of a 7ft for the antenna to resonate for 12-10m bands.

Hey all,

I've decided to go forward with building my own antenna in the attic so it's not visible from the outside. I'm aware of the limitations but this is the only option I have for now. Besides, it will be a good, simple project for my 1st antenna attempt.

It'll be a vertical ground plane for the 12-10-meter bands, tuned with an antenna tuner so the dimensions don't have to be exact. Since it will be in the attic, the vertical space is limited; from ground to the ceiling, it's about 7' high and I have 16' wall to wall for the horizontal elements. I'll also have a top hat made from shorter horizontal elements. Since this is my very 1st antenna build, I wanted to keep it simple and just purchased a few SO239 connectors to experiment with and will provide everything else myself.

I basically need some help determining approximate length of the horizontal elements for the top hat and the ground plane, if the vertical element is 7' long. I don't know if there is a formula or if I simply have to experiment with it, but I've read on another thread on here that I can simply use 8 wires running horizontally to all directions for the ground plane and use 4 wires for the top hat, but don't know what their lengths should be, for it to resonate on 12-10m bands.

Thanks in advance!

 

[K6GBW]

If you’re talking about a quarter wave ground plane then seven feet isn’t going to work. It would need to be about 8 1/2 feet to work properly. To be shorter you’ll need a loading coil to make up the difference. As a suggestion, you might try just getting an 11 meter mobile antenna and create a ground plane for it. I’ve done that using a center loaded CB antenna called a “Monkey Made” and then used 8 foot lengths of wire attached to the mount to create the ground plane. With a tuner you can make it work on 10-11-12 meters. It’s not pretty, but since it would be in the attic it doesn’t really matter.

 

[W4AXW]

Not sure why a Vertical GP is absolutely necessary. A number of wire antenna designs would be much simpler to stuff in an attic and would probably be more efficient. Center-fed half-wavelength Inverted Vs would be my first choice in the attic.

 

[IrvingtonVFD43]

I have an inverted VEE in the attic. I use speaker wire cut for 10 meter ham band to about 8' 1/4" for both legs, sloped 45 degree angle like an upside down V. It is also efficient over on 11 meters. It beats my end fed long wire antenna hands down on the above stated bands.

Very cheap and easy to build. Just need speaker wire, or any kind kind of suitable wire, a 1:1 Balun from LDG electronics, (or equivalent) and a high place in your attic where you can install the antenna and slope the wires down at an angle.

Here is a good place to start if you want more information:

Inverted V Antenna - A popular Dipole variant | VU2NSB.com - Amazing Amateur Radio

An Inverted V antenna is a very popular variant of the standard horizontal dipole. In his article, I will try to bust some of the myths associated with Inverted V and dipoles.

vu2nsb.com

 

[W4AXW]

Another good site for most things dipole:

INDEX to KK4OBI Bent Dipoles website

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