[TowerTalk] Tower Insulators-Additional

[n4kg@juno.com]

Ron,

The BEST way to electrically lengthen an element is END / TOP
CAPACITIVE loading.  This increases the current in the radiating
portion of the element improving efficiency and offers the greatest
bandwidth.  

Top loading a thin mast will also improve current flow through the 
diameter reduction.  It is well known by designers that current 
distribution through a large reduction in diameter is greatly
reduced compared to a continuous element.   This is why low 
band Yagi elements need to be physically longer than 1/2 WL.

Base loading with a coil is the WORST method of loading a short
element.  The coil REDUCES current in the radiating element and
has the LEAST bandwidth of any type of loading. 

The Butternut HF2V is an example of this.  It is full size on 40M 
and is base loaded on 80M.  A friend has an HF2V with 120
radials.  It works quite well on 40M.  On 80M it is considerably
less effective than a vertically polarized Delta loop and an inverted
Vee, both supported at 90 ft.

de  Tom  N4KG

On Tue, 4 Apr 2000 10:10:17 -0000 "Major Ron" <majrabsr@rconnect.com>
writes:
> 
> Thanks guys,
> 
> I should probably add some information. My reasons for wanting to 
> insulate
> the tower bases was to add an inductor to electrically lengthen the 
> height
> of the radiators, as well as provide a match. This  would be 
> attached
> between ground and tower base, so DC ground would be maintained.
> 
> I just had an antenna hit by lightning, so that is important 
> consideration.
> 
> Also plan on using top section of guys as capacity hat, finishing 
> the guying
> with Phillystran or equivalent.
> 
> I know the important thing is to make all the radiators alike. An 
> extensive
> ground system (at least 60 radials per tower) is in the works.
> 
> Thanks,
> Ron, KA9ALC
> 
> 
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