The lengths of coax from the center circuit board must be identical. Note that the layout of the antenna switching diodes on the experimenters PC board is symmetrical. Whatever you do, make the unit collapsible so it can be stored when not in use. I used wing-nuts on the antenna elements to allow the unit to fold easily. It is very important that the diodes on the antenna be connected as shown on the schematic.
Most diodes have a band which shows which end is the cathode.
The best diodes for use in the antenna are RF PIN diodes. I used 1SS103 PIN diodes I purchased at a flea market. An equivalent diode is the MPN 3404. In a pinch, you can substitute a 1N4007 power diodes. They have a similar internal diode structure to the PIN diodes and will work almost as well.