2M ( 144Mhz ) 70CM (430 Mhz) Coax Collinear

This is a simple and quick design for a collinear antenna. Covering 144 Mhz – 146 Mhz and 430 Mhz to 440 Mhz. It can produce similar results to a commercial version and be made from scraps of coax. Depending on the mounting location, coax used etc. The 70 CM band may be limited.

colinear

To construct this antenna you will need a length of at least 130 cm RG58 coax. The main part of the antenna is all one piece. The smaller diameter sections are the inner conductor of the coax with its insulation. The larger sections are the complete coax.
To create this antenna you will need to measure the correct lengths for the sections and mark them. It is easiest to start with the bottom section.
Measure 288 mm of coax. You  will need to have a little extra at the bottom to make connections as shown. At the 288 mm mark, carefully remove the outer plastic and the metal braid. This will just leave the inner conductor and its insulation. You need a section 360 mm long with the outer plastic and the braid removed.
Repeat the process for the next two sections. Now make the 35 mm stub in the same way.
At one end of the stub the inner conductor needs to be soldered to the metal shield.
Now connect the inner conductors of the main antenna and the 35mm stub together and connect the outer braid of the stub and main antenna together.
The circle symbol represents a socket for connecting a feeder.
This antenna does not need a ground plain but one can be added if you want to.
If carefully constructed you should be able to achieve a VSWR below 1.2-1. This antenna can be rolled up and used for portable operating or placed inside a fibreglass rod  or length of hose and put on a roof. Like all collinear’s it is sensitive to near by objects. Tuning should be done outside as close to the position as possible.
Enjoy.

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