The usual configuration of an 80-40 trap dipole has 40 Meter traps at
about 33 feet from the center. The remaining wire is less than for a
full half wave on 80 Meters since the 40 Meter trap acts as a loading
coil on 80. Length may be less if you have 20 Meter traps as well.

If you have enough room for a little over 100 feet, you may not need
any additional loading coils. You also might reduce the total length
some by increasing the inductance-to-capacitance ratio of the traps.


I don't think he will have any problem getting that antenna in at under
100 feet with out using extra inductance at the ends. My 75M dipole
trapped at 40M is right around 100 feet, I think. If he adds 20M traps
they will surly shorten it even more.


Ed