TopBand: Inv-L vs HD special?

[Eric Gustafson]

>Date: Tue, 11 Feb 1997 14:44:21 -0500 (EST)
>From: Lee Wells <leewells@lexmark.com>


Snip (brevity) ...

>
>The SWR is less than 1.5:1 from 1.80 to 1.91 MHz.  The dip is currently
>at 1.835 with what appears to be 1:1.  From what I've read, this seems
>fairly broad, so I'm guessing I have a lot of ground losses.  The SWR did
>change from Sunday night to Monday night.  It seemed to "shorten"...enough
>to move the dip up about 40 KHz.  I didn't change anything though...the only
>noticable difference is that the ground was frozen last night, where
>it wasn't Sunday night.
>

I can shed light on this phenomenon.  Frozen things are typically non
conductive.  When your ground froze, the conductivity of the frozen portion
fell to near zero.  If you doubt this, stick a couple of ohmmeter probes in
a plastic ice tray with slightly salted tap water in it and put the tray in
the freezer.  If you didn't use enough salt to keep the water from
freezing, then you can detect the exact time that freezing was complete by
monitoring the measured resistance.  Your antenna saw the distance between
its phase center and the conductive portion of earth below it increase
slightly.


Snip (again) ...


>3) Forget the long elevated radials, and put them on/in the 
>ground.  Also from what I read its a better trade to have
>more shorter radials (1/8 wave) than a few long ones.  I'll
>probably put in 16-20 (1/8 wave) radials instead of the 4 
>1/4-wave ones.  And make them as straight as possible.  Plus
>the elevated radials get in the way, especially when mowing season
>starts.
>

This is probably a good idea in this case.  Figure out how long they _can_
be.  Then put in however many it takes to get the tip to tip distance
between radials down to 0.03 wavelengths (about 26 for 1/8 wave radials).
That will get you to the diminishing returns zone for radials of that
length.


Snip (some more) ...


>
>PS - I used wire with "purple insulation" for the radials....does this
>add to the kharmic balabce????  :-)   (Hey it was a little cheaper).
>

Yes, the K-balance will be much better.  But purple is the royal color.
And as you have already noted the (slightly) elevated purple radials are in
fact a royal pain in the rear!


73,  Eric  N7CL

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