The HP 117A puts out +35 VDC for the 10509A antenna.
According to the HP 117A manual and subsequent manual change pages there are four versions of the 10509A 60 kc WWVB loop antenna. Early units used a pair of 13CW4 Nuvistor tubes for the preamp but later units (starting with series 1348A) used a different design based on a dual N-channel FET. A crystal filter was used in early versions but later units (starting with series 1432A) used tuned inductive coupling instead. NOTE: If you replace these inductors (L1, L2, L3, or L4) observe that both their proximity (about 1 mm) and their axial orientation (due to wire-wind direction) is critical for correct operation.
See the following schematics for details.