[Towertalk] Why capacity hats on 40-2CD

[Joe Subich, K4IK]

AO tells me that the capacity hats on the D-40 (or 40-2CD) 
shorten the element tips by about 26 inches.  Ran my D-40 
(40-2CD) driven element model with and without the capacity 
rods ... and the tip had to be extended 26 inches to 
resonate at the same point without the capacity rods. 

Similarly, to maintain a constant tip length one would need 
to increase the loading coil by almost 50% (from 12.9 uH to 
18.6 uH) which assuming constant coil Q (not likely with the 
small diameter coil) would represent an increase in loss of 
about .5 dB (which might cause coil failure at 1500 watts 
of high duty cycle modes - RTTY, contest, etc.). 

73, 

   ... Joe, K4IK 
 

> -----Original Message-----
> From: towertalk-admin@contesting.com
> [mailto:towertalk-admin@contesting.com]On Behalf Of Pete Smith
> Sent: Sunday, April 14, 2002 7:26 AM
> To: towertalk@contesting.com
> Subject: [Towertalk] Why capacity hats on 40-2CD
> 
> 
> The subject line almost says it all.  This question originated because 
> a friend and I were speculating about replacing the linear loading 
> on a Force 12 EF-240S with lumped inductance, placed at the same point 
> in the elements where the linear loading is now connected.  I described 
> it as a scaled-down 40-2CD, and then wondered why Cushcraft put the 
> little capacity hats on the outer end of its loading inductors.  To 
> shorten the elements a little?  Change the current distribution?
> 
> 73, Pete N4ZR
> 
> Check out the World HF
> Contest Station Database at
> www.pvrc.org
> 
> 
> 
> 
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