HF?? It's hit or miss whether you'll hear much at all.
The standard frequency spectrums for aviation are
VHF 108 -117.975MHz (navaids -vor/ILS)
VHF 118.000-137MHz (ATC/FSS comm)
UHF in the range of 215-387MHz (Military comm, UHF nav -Tacan) most civilian ATC units may only have one or two UHF frequencies available to accomodate mil. flights.
HF was common until the 50's but as VHF came along it was far superior for direct communication. When I got into ATC in the 70's HF was mostly gone from everywhere but FSS who relayed position reports to ATC.
The HF bands are not used for 'normal communication' except over long distances - the far arctic and oceanic routes for example that are beyond VHF line-of-sight range. As HF is atmospheric-dependent it's use is unpredictable and sometimes awkward. More and more countries are installing VHF repeaters in remote areas to reduce the need for HF. Most of the traffic you'll hear will likely be aircraft position reports transiting the Oceanic corridors, or company communications (Flight Ops for example- but even less of that now) A frequency list can be found here:
http://www.grove-ent.com/mtmwara.html
Because of the atmospheric issues (skip, etc.) you can get some "wierd" stuff - like hearing one half of a communication from a station hundreds or even thousands of miles away, and not be able to hear the other side which may be close-by. Also a given frequency may work for a while and as soon as the aircraft has moved that freq. is lost. The quality basically is poor because of the lower frequency range. Fun to listen to occasionally, but I wouldn't spend the money to listen.
Rob
