VC01 will probably change frequencies about the 1st of the month. It used to change freqs on about the 6th of each month, but recently it has been changing about the 1st. It moved to the current frequency set before 4 January.
4978 kHz USB is one of four frequencies that should be in use at this time, although only two total would have been active at the time you took the recording. Typically the station has two sets of two frequencies, one in USB and one in LSB with the pair separated by a few MHz, and it changes freq sets twice a day. These are probably day and night freqs, and they appear to be frpm different locations. So two freqs (and possibly two locations) in operation for about 12 hours, then switching to the other set of two freqs.
For the last 12 months or so, at the minimum of the Solar Cycle, VC01 has been weak and less often heard at my location. I could generally always find at least one freq, but weak and poorly heard. For the last couple months it has been getting better. In about a year you should be hearing both freqs pretty fair on the North American West coast.
T!