[Lowfer] Dew?

[Ed Phillips]

Eric Smith wrote:
> 
> Now that I have the rf current meter I'm seeing things I never saw before.
> Overnight, my antenna current drops a few mA.  After morning, it rises
> again.
> 
> So I've looked at what's different about nighttime.  Well, for one, it's
> dark -- noticed that right off.  Also, the temperature drops.  Noticed
> that, too.  Hey, I may have been born at night, but it wasn't *last*
> night.
> 
> The other thing I noticed was the dew.  Here in NE OK there is lots and
> lots of humidity that comes up from the gulf.  It's amazing -- I can visit
> my sister in the panhandle of Texas, and it can be 100 degrees and not
> even feel like it.  But here, once it gets over about 80 or 85, the heat
> combined with the ultra high humidity makes it very uncomfortable.
> 
> So at night, if the conditions are right (usually) there is dew -- often
> heavy dew.
> 
> Last night was no exception.  My antenna was soaked, the grass, and
> everything.  I don't know if it's because the meter was soaked, or the
> antenna, or the grass, house, etc, or if the dew even has anything to do
> with it at all, but the antenna current definitely drops.
> 
> Am I on the right track?  Do any of you know?
> 
> Thanks,
> Eric

	You are.  The antenna for the IZJ beacon is a 50 foot Hygain tower
supported on 12 isolantite insulators (it's a heavy sucker and the wind
loading can be pretty large).  Light drizzle or even heavy fog deposits
enough moisture on them to increase the losses (they are in parallel
with the base of the tower, which is a high impedance point) and drop
the antenna current way down; this is on a setup which is pretty lossy
to begin with and has a low parallel resonant impedance!  I find that
cleaning them and spraying them with silicone spray helps make the
moisture bead up and reduces the effect. 

Ed