[Elecraft] Trap designs with toroidal inductors

[Stuart Rohre]

Well Mike,
Another reason besides the mechanical complexity of mounting the fragile
cores in a trap configuration outdoors and weather proofing it, is the fact
you might in an antenna want to spread out the inductor for three reasons.
1) High Q for lowest loss. 2)  A solenoid coil does not bring the high
voltage ends close to each other like a toroid might.  3) It is more than an
inductor, and you might as well let the solenoid length add to the radiation
of the antenna, and not self shield the inductor as the toroid tends to do.
Thus, the solenoid trap can add to the length of radiator.  Most solenoid
coil traps either incorporate the capacitor inside the coil, or use coax for
distributed inductance and capacitance, or use a weather shield over the
coil as part of the capacitor.  Although that shields the trap from
radiating, it does provide a better weather resistance if done right.  Note
though, that those metal can traps have plastic end boots that fail from sun
effects over time.
73, Stuart K5KVH