Topband: Making your own Base Insulators

[Dick and Adele Bingham]

Greetings everyone

In the past I have made my own base insulator for R-25 towers. To do so, I drilled three 1"-diameter holes in
the HBP-25 in which I inserted some machined insulating spacers. These spacers insulated the mechanical
connection between the base-plate and the hold-down bolts embedded in the concrete base. Separating the
bottom of the HBP-25 and the concrete, I used several thick sheets of insulating material (if I remember
correctly, it was either several thicknesses of 1/2" plexiglas or ABS sheet-stock salvaged from a plating
tank.

The insulated base made it a simple job to feed the antenna. The only excitement it ever produced was a 
significant local fire around the base of the tower when the plastic-box housing the antenna tuner assembly 
caught fire. Boy, did I do some fancy foot-stomping shortly after noticing the amplifier started behaving badly! 
There-after, I kept the area around the tower free of dried grasses and used more robust components in the
new tuner.


              HBP-25 Assy.                                                       |<-------- ~2" -------->|
             |---------------------------|
             |   O                 O  |  The 3 "O's" are the added         |-----------.   .------------| Phenolic material
             |             /\            |  1"-holes drilled in the                |------|    .   .    |-------|
             |           /    \          |   base-plate                                     |    .   .    |
             |         /        \        |                                                       |----.   .----|
             |       /            \      |
             |     /----------------\    |                                                  Insulating Spacer
             |             O            |
             |---------------------------|

73 de Dick - W7WKR  CN98pi