Topband: Capacity hats - cylinder form

W2pm at W2pm at
Sat Sep 16 13:09:32 EDT 2006

I was reading in an old 1944 U miliary manual - TM 11 - 314 Antennas and  
Antenna Systems a good deal of material on top loaded verticals for 1 - 2  mhz.  
The author writes of several forms of capacity hats - disks, spheres  and 
cylinders and notes a wire or skeletal form has nearly same effect as a  solid 
form. There is included an interesting table of capacitance values for the  3 
forms and the cylinder form appears to most dense.   (i.e. a 36 inch  diameter 
cylinder has 70 uufd while a 36" diameter dish has 50 and the delta  increases 
with size).
Aside from that in Bill Orr's last book - HF Antenna Book - it shows a top  
loaded vertical by KY3F which uses a cylinder form constructed from plaster 
wire  mesh - seems fairly simple and maybe easier to deal with in a tight space 
than  the disk.
Has anyone here made a cylinder form capacity hat?
73 Pete W2PM

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