The TS-450/690 may not calibrate properly against WWW (JJY) when using the calibration cable that is supplied with early versions of these sets, (serial numbers below 311xxxx) and when an antenna that is shorted for DC is used. A dipole with a balun is a prime example of a DC shorted wire. A minor circuit modification that adds a 100 pF isolation capacitor should also be performed. Please refer to the diagrams below for modification notes.
E37-0280-05 Calibration cable assembly 1 Ea.
CK73FCH1H101J 100 pF capacitor 1 Ea.
Time required for this modification is 30 minutes.