Re: A useful Dont


John G3UUT
 

Another useful Don't;

Don't seal up the hole or the gap usually provided at the bottom of a vertical antenna, the type with a plastic or fibreglass shroud and connector on the bottom with either a hole near the connector or a gap between the connector assembly and the fibreglass.

I very carefully sealed all round the connector and covered the hole and gap of my nice shiny new 2m/70cm/23cm vertical.  A year later I wondered why it wasn't working and the SWR was very high.  Taking the antenna down, you could see through the translucent plastic that there was about 3 inches of water at the bottom.  I thought that the shroud must have a hole where rain was getting in but it was water tight.  This taught me a useful lesson in that watertight is not necessarily water vapour tight and that heating and cooling can draw in damp air in the evening through pores in the structure which then condenses.  It doesn't go out as easily as it goes in so the condensation builds up over time until it causes a problem.

73 John G3UUT


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