ANTENTOP- 01- 2008, # 010

Water Pipe T-Joint at VHF Antennas

4. Antenna elements are fastened without drilling the traverse.

5. Avoid screw, nuts and clamp in fastening of antenna elements.

6. T- joint is mechanically strong the antenna element.

7. Weight of one antenna element in length of 1 meter made from of a silumin tube in 10-mm OD with the T- joint was only 70 grams.

8. Antenna made by step by step stringing of the T- joints with already installed there antenna elements.

How to use T- joint at antenna? Picture1 and 2 show the way. However, some advices are below. Take T-joint that has ID closest to a diameter of antenna traverse. If the T-joint has ID

Less the diameter of antenna traverse you need gnaw through to obtain needed ID. Leave wall thickness not less the 2 millimeters.

Do ID on to 0.5- 1 millimeters less the OD of the traverse and do longitudinal cut in the lower part of the T- joint. At the case before installation of the T- joint to the traverse a small thing (like wooden or metal bar) should be inserted into the cutting. See Picture 3. When the T- joint is sitting at the right place at the traverse just remove the bar and the T- joint would be fastened well to the traverse.

Picture 3.

It is possible hard fastened the T- joint to the traverse by 1-2 small screw. Another way for hard fastening- put some glue in to pipe-bend. The pipe- bend was closed by a plastic washer and epoxy. ( See Picture 3.)

Holes for antenna elements should have ID on to 0.2- 0.5 millimeters less the OD of the antenna element. The holes should be drilled with drilling machine. T-joint at drilling should be placed on to horizontal table of the drilling machine. Antenna elements go through the holes with pressure but then hard fastened at the T-joint.

Active dipole vibrator made from two halves may be fastened to T- joint with help of a plate made from a good and mechanically hard insulated stuff. It may be thick PC, thick plexiglass.

The plate is fastened to cut side tap. See picture 4.

Picture 4

However, it is possible to insert two half vibrator into a thick rod from an insulated stuff, then the rod with the active vibrator is fastened into the T- joint above mentioned ways (See picture 2, 3)

T- joint was tested to strength after being three hours at minus 28 degrees Celsius. Attempt to break the T- joint pooling of the antenna element (fastened inside the T- joint) is failed. Antenna element was broken (4-mm OD silumin) , T-joint- no. It was tried to break the T- joint with help of a hammer. Hammer left only slight dent on the T- joint but no any crack.

Using prepared T-joints (with drilled holes for antenna element and traverse) it takes from me only several hours to assemble 7- elements VHF antenna. Hope, it will work long time for me. See picture 5.

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