ferrite antenna impedence matching
WWVB transmits at 60 kHz and thats barely above audio in the whole realm of radio so impedance matching to reduce VSWR or prevent reflections is of no consequence. Rule of thumb is that if a feeder length approaches one-tenth the wavelength then start thinking about it. 60 kHz has a wavelength of 5 km so don't bother thinking about it.

In fact if you looked at the characteristic impedance of a coax line at 60 kHz it would be "complex" and not resistive but, like I said it doesn't matter.