[Antennas] Trap design considerations

[Tsachy L]

Hello Gurus
I'm trying to develop a "Classic Quarter Lambda trap vertical" for 12m & 17
m ("Classic" in the sense of the trap divorcing the 17m section ).
I've seen some remarks about specific L/C ratios to stay with, about 200 Ohm
reactance at resonance to stick to, but  I don't have any reliable
source or explanation on the matter.
So actually what I'm asking is what are these special considerations in
designing such a trap (beside physical dimensions  vs. power handling)?
All info is welcome.
Thanks in advance, Isaac, 4Z4TL
       http://www.iarc.org/~4z4tl/
ernie@netvision.net.il  4z4tl@iarc.org