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Asunto:[dxcolombia] 160m Vertical
Fecha:Jueves, 8 de Junio, 2006  10:27:36 (-0400)
Autor:Alexis Deniz M. 4M5DXgroup <yv5ssb>



160 Vertical

This is a 90 foot tall top loaded vertical for 160 meters. It is constructed from aluminum irrigation tubing and has four sets of four guys each. The top guys also serve to support the top load wires.  It has a "temporary" wire  stub about 68 feet long  hung off the side to provide operation on 80 meters. More details are pictured below.


The  most important part of any vertical antenna system is the ground. I like to put the radials in the ground before putting up the antenna so that the antenna and guys are not in the way. This is the implement I used to form shallow trenches for the radial wire to lay in. The local farmers use these to form corrugations in the field for irrigation water to run through.


Here is one of the shallow trenches formed prior to inserting the radial wire. The orange baling twine is streched out between the vertical base and far end of the path I want the radial to take. That gives me a guide to follow with the tractor. I tried to insert the wire in the ground as I pulled the trench but there were too many rocks. Wound up inserting each wire by hand. I figured that I walked about 18 miles putting in the radial system.


Construction was started by first  locating and pouring five concrete piers for the guy anchors and base. All five are similar except the guy anchors have rings instead of a threaded stud. After the cement work was done, conduit was placed in the ground for the coax and control cables. You can see the conduit in the upper left of the photo. Next the radials were placed in the ground using the implement shown above, and terminated in a ring around the base. The green wires are used for connection to the tuner box to be installed last. The wires are all soldered to a ring formed from copper wire. When all the soldering is completed the ring was painted with several coats of common PVC pipe cement and then sprayed with Krylon paint to weatherproof the solder joints. There are 82 radial wires, each 100+ feet long.


The mast is constructed from 4 inch irrigation tubing. The guy lines are fastened to the mast with a "wheel line" hub clamp. Using a clamp allows adjusting the placement of each guy set to minimize mecahnical resonances. When the mast was first stood up, I watched as the wind caused vibrations. The mast was then lowered and the position of each clamp was adjusted. The distance between each guy set is now different and vibration is minimal.

The guys are temporary baling twine. I used it to establish the proper lengths and when the design was stable, changed to Dacron.


The base insulator was made from pieces of PVC pipe. I turned various pipe fittings on my small lathe and used PVC pipe cement to bond them all together. The 1/2 inch diameter hole is for the hinge pin. The first insulator was made from ABS. The ABS got brittle when the temperature dropped way below freezing and cracked. So far the PVC has not failed.


The mast is fabricated from aluminum irrigation tubing. The bottom 40 foot is 4 inch diameter, 0.075 inch wall tubing. The next 30 feet is 4 inch diameter, 0.05 inch wall tubing. The top 20 feet is 3 inch diameter, 0.05 wall tubing. I tried a couple different approaches to splicing the sections together before it became obvious that more internal support was required to keep the tubing from collapsing under severe load conditions. This splice was made from PVC conduit. The pieces were turned on my small lathe and make a snug fit inside the two pieces of 4 inch tubing. It didn't need to be made from insulating material but that's what was handy. A sleeve made from a 1 foot long piece of 0.05 wall tubing to fit over the outside of the joint. Sheet metal screws through the tubing and into the  PVC keep the whole thing together and provides electrical continuity.


A base was formed from 4 inch steel "C" channel. The pieces were welded to form hinge points for the mast and gin pole. The base plate is bolted to the cement footing. 1/2 inch diameter bolts form the hinge pins. In this image, the tubing on the left is the gin pole in the lowered position and the antenna is on the right in the raised position. The black base insulator is the old ABS insulator that failed after this photo was taken.


The gin pole is a single 40 foot piece of 0.075 wall tubing. Although difficult to see in this image, the 90 foot vertical is on the ground to the left with all guys in place. The top of the gin pole has a guy on each side, a triple line pulley system to the rear, and four guys to the mast. As the pulley system pulls the top of the gin pole down, the vertical is raised up. This is a one man operation. I wanted to get a photo of the thing half raised but couldn't figure out how to hold the rope and run the camera at the same time!


In this image, the gin pole is in the lowered position. The side guys are the orange baling twine. The four rasing guys on the mast are black dacron. The yellow rope is part of the two line pulley system. It was later changed to a three line system to allow raising the mast with less effort on my part. The rope is tied off to a board. Not shown in the image is the tractor parked on the board! This was later changed to a pemanent concrete anchor point.

The four raising guys are tied off after the mast is raised. Another set of full length guys are used to secure the mast from the "forward" direction


This is the tuner box at the base of the vertical. There are four open frame relays used to switch in different "L" networks. Only two are used now, for 160 and 80. The relays and network parts are mounted on a sub-chassis so that it can be easily removed and modified in the shack/shop.120 VAC is provided for soldering irons and test equipment. In the lower left the bottom of the mast can be seen in the shadow. You can see part of the stand off insulator for the bottom end of the 80 meter side mounted stub.