[TowerTalk] mid-point loaded beam elements

Chuck Counselman ccc at space.mit.edu
Mon Apr 7 17:24:02 EDT 2003


At 1:56 PM -0400 4/7/03, K3BU at aol.com wrote:
>Use plastic soft drink bottles....


For best Q, the coil should have a single-layer winding, be as large 
as possible dimensionally subject to the requirement that its 
self-resonant frequency be well above the operating frequency, and 
its length should be between 50% and 100% of its diameter.  The 
conductor should be as thick as the length of the coil, the number of 
turns, and safe interturn spacing allow.  (Thus, you may be using 
copper tubing rather than wire.)  A 40-meter loading coil may be too 
big to fit inside a soft-drink bottle.

Spreadsheets are available for designing coils.  IIRC, QEX had an 
article about this last year.

73 de Chuck, W1HIS




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