Low Band Dipole Covers 160-80-40 meters with an overall length of only 100 ft. Antenna performance and 2:1 VSWR bandwidth is site dependent and varies with height above ground and surrounding objects. The typical bandwidth is:
160M – 20kHz • 80M – 40 kHz • 40M – 300 kHz
Full band coverage can be accomplished with an antenna tuner.
Model DX-LB PLUS, same as Model DX-LB but adds parallel wires for operation on 20 thru 10 meters.
As you can read, from the instructions, this antenna has NARROW bandwidth on 80 meters (40 kHz) and 160 meters (20 kHz). Since you have the PLUS model, there will be some interaction between the wires in this fan dipole configuration.
FIRST, determine where these 2:1 points are on 80 and 160 meters.
SECOND, decide where you are going (SSB/phone portions of band are shorter wavelengths)
to move the 80 and 160 meter segments.
THIRD, it is easier (and cheaper) to shorten elements, than trying to lengthen.
FOURTH, Use the old standby formula: 468 / Frequency (in MHz) = Total Length (in Feet)http://www.hamuniverse.com/dipivcal.html
The ISO-RES coils eliminate a specific length of wire --
you should be able to determine this for each coil with simple math
based on antenna's current frequent dip point and wire lengths.
BTW, are the coils on this antenna doing double duty as both loading coils and traps? Quite a trick.
NO. A trap requires Inductance (L) and Capacitance (C) .... your ISO-RES coils are not L-C traps, just Inductance (L) / loading coil.
K7MEM calculator for shortened antennashttp://www.k7mem.com/Electronic_Notebook/antennas/shortant.html