Need homebrew antenna help! Building a vertical.

[w4wxp]

I have taken this antenna design, Build your own 20m vertical by dxzone.com, and I have some very, very tall trees in the back of the property.

I have 75 feet of wire to work with for a vertical element, and I was wanting to use 75 and 40 meters.

I know that people use non-resonant 43 foot verticals (ala the s9, etc) for 75 and 40, so would 75 feet of wire work even better? Or would there be a good length to cut it at that would be optimum for 40 and 75?

I realize that even at 75 feet, it wouldn't be a quarter wave for 75, but some signal is better than none!

Ideas, antenna aces? Thanks in advance,

Chris

 

[LtDoc]

A 1/4 wave for 80 meters is about 66 feet long, so you'd have more than enough for that. A 1/4 wave for 40 meters is something like 33 feet long, nd for 20 meters something like 16.5 feet.
An 80 meter vertical will probably be usable on 20 meters, but not on 40 meters. Of course, with a fairly good tuner, an 80 meter vertical can be made to 'work' almost anywhere. Not the best in the world, but it'd work.
With any vertical antenna, a good ground system if a requirement. If it's going to be at ground level, figure on several radials as long as you can make them. You can't have too many radial, and being longer than a 1/4 wave in length isn't a draw-back at all. Don't have a clear 65 - 70 foot radius around your vertical 'tree'? Zigzag the things, it works. How deep? Deep enough you don't trip over them or wind'em up in the lawn mower. How many of the @#$ things? How about 3 more than whatever you've got planted when you are totally fed up with them? That sounds about average.
Have fun.
- 'Doc

 

[prcguy]

In addition to the ground radials LtDoc mentioned you can also run multiple vertical wires for several bands and eliminate the tuner at the feedpoint.

A wire around 66ft and one about 33ft would give you 80m, 40m, 20m and 15m. You would need to separate the wires at the end by a foot or so using a short PVC pipe or chunk of Plexiglass rod.
prcguy

 

[n3qv]

For multiband operation of decent vertical and horizontal radiation patterns. Try an "L" antenna. Pull the vertical portion up in the tree and then extend the leg horizontally in a direction that will get you the best coverage in the areas you require. Feed with 450ohm ladder-line and use an good antenna tuner.