Post by homerbb on Mar 17, 2011 23:11:46 GMT -5
I put up the 4 element Yagi my neighbor and I built, and put a vertical dipole above it. The dipole seemed to work as well as any dipole I'd had, but I was accustomed to vertical antennas with gain, so I decided to put something else up. I pulled down the dipole and put up a 1/4ƛ GP which actually proved to serve me better than the 1/2ƛ dipole above the Yagi. However, I was going to turn the dipole into a vertical GP, and went with a 5/8ƛ. I wanted less wind load than I had experienced with my previous 5/ƛ antennas, and thought I could accomplish this by reusing the dipole materials, and using shorter, smaller diameter radials. I chose to use 3' long x 12 radials for a full equivalent of 9' long x 4 radials.
Here's what I did:
I started with a common wire spool available for free from Home Depot if you catch them before the throw them out.
I purchased 12 0f these 3' garden stakes for radials. They are light, of small diameter, and are plastic coated metal.
I removed the ends of the cable spool from the core.
I drilled holes through the disc for attaching the radials with cable ties, and threaded the cable ties through.
I started putting the 12 radials on the disc in this fashion.
You'll notice I use the built in ridges on the disc to maintain my exact distances apart for each radial.
I used self-drilling screws at the inner end of each radial to both secure the radials, and to use for wiring them together. The inside circular hub of the disc was a natural marker for getting all the radials at exact length.
The completed radial set gets a coat of silver paint to improve its appearance
The coil.
These items, a spacer, which will be used to mount the coil, and the coupler will be used to mount the radials disc to the antenna shaft.
The dipole consisted of two aluminum tubes 3/4" x 6', and two aluminum tubes 1/2" x 2.5'. They were bonded in the center by a 1/2" x 1' PVC tube inside the 3/4" aluminum tube, and a 3/4" x 1' PVC tube outside the 3/4" aluminum tube. The dipole was separated by 1" of space. For the 5/8ƛ I closed the gap, and tied them together on the outside of the PVC tubes by use of metal Duct tape, and copper wire between self-drilling screws. The 5' long fiberglass post hole digger handle will be the bottom shaft of the vertical as it was for the dipole.
I have the entire vertical assembly together here. For the additional top length needed an old A99 top peice was inserted and secure with screws tapped into the metal knurl at the bottom of the whip.
The coupling is assembled to the fiberglass base shaft, and the hub is attached to the coupler. All this is accomplished with tape for spacing, and self-drilling screws. All is together and the tap point is being sought for.
The antenna is in the air on a temp mast in a temporary place.Its final location will be over the Yagi on the tip over mast. The entire thing will be painted silver in it final condition.
Where it is currently mounted is is nearer the house than I like. And there is also a tree nearby. The photo angle gives a false impression of its nearness to the roof ridge. It is about 12' the other side of the ridge, and two feet higher. In this location the SWR curve is:
28.755 ---------- 2.3:1
28.305 ---------- 2.3:1
27.855 ---------- 1.9:1
27.555 ---------- 1.4:1
27.405 ---------- 1.3:1
27.205 ---------- 1.1:1
26.965 ---------- 1.0:1
26.515 ---------- 1.3:1
26.065 ---------- 2.1:1
25.615 ---------- 3+
I hope the curve will settle a little flatter with distance from the ground on the permanent mast. However, it is good for my usage as it is.
Here's what I did:
I started with a common wire spool available for free from Home Depot if you catch them before the throw them out.
I purchased 12 0f these 3' garden stakes for radials. They are light, of small diameter, and are plastic coated metal.
I removed the ends of the cable spool from the core.
I drilled holes through the disc for attaching the radials with cable ties, and threaded the cable ties through.
I started putting the 12 radials on the disc in this fashion.
You'll notice I use the built in ridges on the disc to maintain my exact distances apart for each radial.
I used self-drilling screws at the inner end of each radial to both secure the radials, and to use for wiring them together. The inside circular hub of the disc was a natural marker for getting all the radials at exact length.
The completed radial set gets a coat of silver paint to improve its appearance
The coil.
These items, a spacer, which will be used to mount the coil, and the coupler will be used to mount the radials disc to the antenna shaft.
The dipole consisted of two aluminum tubes 3/4" x 6', and two aluminum tubes 1/2" x 2.5'. They were bonded in the center by a 1/2" x 1' PVC tube inside the 3/4" aluminum tube, and a 3/4" x 1' PVC tube outside the 3/4" aluminum tube. The dipole was separated by 1" of space. For the 5/8ƛ I closed the gap, and tied them together on the outside of the PVC tubes by use of metal Duct tape, and copper wire between self-drilling screws. The 5' long fiberglass post hole digger handle will be the bottom shaft of the vertical as it was for the dipole.
I have the entire vertical assembly together here. For the additional top length needed an old A99 top peice was inserted and secure with screws tapped into the metal knurl at the bottom of the whip.
The coupling is assembled to the fiberglass base shaft, and the hub is attached to the coupler. All this is accomplished with tape for spacing, and self-drilling screws. All is together and the tap point is being sought for.
The antenna is in the air on a temp mast in a temporary place.Its final location will be over the Yagi on the tip over mast. The entire thing will be painted silver in it final condition.
Where it is currently mounted is is nearer the house than I like. And there is also a tree nearby. The photo angle gives a false impression of its nearness to the roof ridge. It is about 12' the other side of the ridge, and two feet higher. In this location the SWR curve is:
28.755 ---------- 2.3:1
28.305 ---------- 2.3:1
27.855 ---------- 1.9:1
27.555 ---------- 1.4:1
27.405 ---------- 1.3:1
27.205 ---------- 1.1:1
26.965 ---------- 1.0:1
26.515 ---------- 1.3:1
26.065 ---------- 2.1:1
25.615 ---------- 3+
I hope the curve will settle a little flatter with distance from the ground on the permanent mast. However, it is good for my usage as it is.
