The CWP feeder is Andy - a friend of mine. It's actually 2 radios on different frequencies being fed into 1 stream. The freq coverage depends on the time of day and propagation. If Andy is about he'll change the freqs to cover the most traffic (unless listening for something specific) - this is often SP (BNE & AKL) and CWP (SFO via Guam relay xmtr or TYO/MNL).
Unlike VHF ATC, HF don't use fixed freqs and they're constantly changing depending on the propagation and time of day/night. Generally the higher freqs are used during the daylight and low freqs during darkness. If you were to leave the radios on set freqs all the time you would end up with about 4 hours of activity and 20 hours of static.
The problem is even worse with the NAT as they have such a huge amount of freqs at their disposal these days and since the loss of the Nova Scotia feeds the coverage from LATC is not great.
For Shanwick daytime traffic they currently use 5649, 6547, 6595, 6622, 8879 and occasionally 10021. For night time try 3446, 3476, 3491, 4675, 5583. For Gander daytime (UTC) traffic, try 8831, 8864, 11279. Gander nighttime (UTC) the bulk of it is on 5616 and 8891.
The West Coast NAT-D feed is currently running SFO full time for CEP1 and CEP2 regions, mainly covering the routes to/from Asia but some Hawaii traffic too. 02-04z runs 8891 but the rest of the time it's on 5547, 11282 and 10057.
Thanks for the detailed explanation. I mainly listen during the early morning hours for coverage in the pacific by sfo and Brisbane center, but it's tough to hear anything as most of the hf feeds are getting the Japan/Philippines traffic.