antenna build question

[Grump]

I'm wanting to try and make a 1/4 wave ground plane with three of four radial was going to use a plastic cutting board and some heavy duty fence wire for all figured cut them to 108 each piece run the vertical straight up then put the radials out at four evenly spaced directions. What I figured I would do was to take a foru inch square of plastic then mount radials pointing to each corner then tie them together with wire hook up shield from coax there then run a lead to vertical mount these on a pole which with this eight would be close to thirty feet at the top. What do you think will it work and be a good setup or will I have to make some kind of matcher for it. Any knowledge will be greatly appreiciated

[231]

It should work okay...about as good as any 1/4 wave vertical I would expect. It should have a lower angle of radiation if you mount the ground plane radials at a 45º angle if you can. And you should be able to get it resonant by simply adjusting the vertical element length...so I doubt you'll need any tuner/matching device. Sounds like a fun project though.

Good luck and let us know how it goes.

['Doc]

One way of going about that is by making that vertical element a 1/4 wave length for whatever channel you use the most. The standard formula ought'a get you close to that (234 / f in Mhz = feet). Then, use the radials to do the matching. Vary the angle they dangle till you get close to 50 ohms or better than about 1.5:1 SWR. That's where I'd quit, getting a lower SWR than that just doesn't do much good. You should end up with a very typical 1.4 wave groundplane antenna.
- 'Doc

[nutcracker]

i think im semi qualified with the 1/4 wave, I have been messing with mine for months. My verticle element is 106'' long and the radials are 101'', That is the lenght that seems to be perfect for mine. My swr is 1.1 on 40 and 1 flat on channel 1. Four radials seem to work best, and I found that running them at a 45 degree angle is best, and to space them is a sqare shaped pattern for best results. The 1/4 wave is probably the easiest antenna to build IMO, you really dont have to be elaborate, since there is no matching device or anything of that nature. Also mine got to a point where the verticle element was 85 inches and the swr was high, that is when you adjust the radial lenght. Also when you attach the center conductor, make sure the shield is not touching the metal on the base of the antenna, or it will produce high swrs. I just bent it so that it is shaped like a U and bolts right to the bottom. Heres a pic or my setup, the ring is just a place for the radials to tie to. It is just easier I think.
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[Grump]

Well I'm getting ready to start putting it together this weekend. I was wondering would it hurt if I put the vertical in a pvc pipe just for strength. I live in the country with no wind blockage and don't want the wind to push my vertical over. The wire I'm using is some heavy duty electric wire fence so it will carry a charge well just dont want to get it up and have one of our spring winds to make me have to take it down. It will be up about 35 foot I'm hoping this will be high enough. Also should I put a ball at the top like mobile radios have not sure what they are called

['Doc]

Grump,
Will it hurt anything if you put it inside a PVC pipe? Nope. Just make sure that the pipe is strong enough to stand up to the weather/wind/sun. There are differences in PVC pipe, by the way, deals with their metal content. The white stuff, rather than the gray/etc, tends to have less 'metal' content. At least from my experience, and I'm certainly no authority on that! Don't like that color? Paint it, with non-metallic paint of course.
That ball at the tip is called a 'static' ball, or a 'corona' ball. Sharp things are more prone to static or corona problems than un-sharp shapes. Making a loop at the tip of that wire should do about the same thing. And since it's enclosed in something, it probably isn't gonna make a huge difference either way. (Ain't the same kind of 'Corona' that comes in a can/bottle!)
- 'Doc

[Grump]

Well I'm going to start this build this weekend and hopefully get her done. I think I'll wait for the corona after I get it up

[Grump]

I was wondering is it hard to build a matching setup if I wanted to build a 5/8 ground plane

['Doc]

No, it really isn't that difficult. I don't have any exact numbers handy, but it isn't that unusual to find them by experimentation. Several ways of going about that, I tend to favor an inductive (coils) matching thingy. Not all that much 'better' than other methods, just easier for me to 'do'. basically the same as 'Imax' uses with their antenna, a variable coil between the feed point and 'ground' (the braid of the feed line). Instead of 'rings', use a ground lead with an alligator clip. Change the tap point until you find the 'right' spot, then quit. Sounds simple, and it is, but takes longer than you might think to find that 'right' spot. Ain't no step for a stepper, but it can take lots of them steps...
- 'Doc