Newly-minted operators often ask what bands they should get on, and whether it's worth getting equipment for certain bands. Here is a very subjective and very biased view of the various ham radio bands available to US hams:

* 160M

• 160M is called "top band" since it is traditionally the longest of the original bands allocated to ham radio. DX propagation is very difficult due to D-layer absorption; propagation behaviour is much like that of AM mediumwave broadcast. It is very, very subject to atmospheric noise and tends to attract very dedicated people with large backyards. There is a 160M SSB QRP frequency at 1.910 Mhz for people who want a double-handicap. 160M can propagate somewhat through a groundwave which hugs the ground and this can give local communication beyond the point of line of sight.

* 80M

• This band still have substantial signal absorption during daytime making it only usable for DX at night. However, 80M seems to be the preferred band for medium-distance nighttime communication, often with NVIS antennae. The CW portion of 80M is active nearly worldwide. The phone portion (often referred to as 75M) is not shared by most non-US-and-Canada countries, and is very crowded with ragchewers who tend to sit on one frequency forever. Much of the stereotype of grouchy and profane old ham radio operators comes from 75M phone, but the CW section is far more polite. There is some groundwave propagation on this band.

* 60M

• This is the newest of the ham bands, established in 2003. Unlike all the other ham bands, it is channelized with only five individual 2.8 Khz wide channels. Because it is so new, many radios designed for ham band use do not support it, and few non-US countries use it. It attracts people who are looking for some place quiet and different. Another oddity about this band is that the maximum power allowed is specified in terms of field strength and not in terms of output power to the antenna, therefore high gain antennas buy you no improvement for transmission.

* 40M

• This is one of the most active of the traditional ham bands. It has good propagation characteristics for nighttime DX even at the bottom of the solar cycle, and medium-distance propagation even during the daytime. Unfortunately it is shared with high powered shortwave broadcasters and sometimes finding a place between all the broadcast carriers can be difficult. 40M collects an interesting mix of ragchewers and DXers. The European 40M phone band is arranged so that it overlaps with much of the Extra phone segment and only a little bit of the General phone segment. If you want to do phone DX on 40M, get an Extra license.

* 30M

• This is a tiny little slice of bandwidth assigned in 1979 by the World Administrative Radio Conference (and therefore not acceptable for QSOs in many contests). Because there is so little of it and because it is shared with other services, it is CW only. The propagation characteristics are much like those of 40M with good DX even at the bottom of the solar cycle.

* 20M

• As we raise up in frequency, there is less and less daytime absorption, to the point where 20M is a very useful band during the daytime. This is probably the most popular band for DX, although band openings appear less frequently than they do on 40M especially during lower parts of the solar cycle. If you have a 60M dipole, it will also resonate well on 20M.

* 17M

• Another one of the WARC bands (and therefore ineligible for many contests), 17M has similar propagation characteristics to 20M although even more sensitive to solar activity.

* 15M

• As we raise even farther in frequency, band openings on 15M are less and less frequent and require a higher level of solar activity. Occasionally there is daytime sporadic-E propagation on this band as well. One of the cool things about 15M is that a dipole tuned for 40M will just about cover 15M as well.

* 12M

• This is one of the newest of the WARC bands. Out of bounds for contesting. Mostly usable only during solar maxima. Propagation seems to be much like 10M.

* 10M

• This band is usable for DX only during solar maxima, really, but sometimes there are short openings due to sporadic-E propagation. 10M openings seem to happen mostly during the daytime. There is a small allocation for 10M FM which is intended for short distance communication but can occasionally be a DX surprise. Much of the problem with 10M has to do with its proximity to the 11M citizens radio band. This has resulted in a lot of "freebanders" using illegally-modified CB gear in the bottom of the band, and it has resulted in laws prohibiting the sales of high-powered amplifiers capable of 10M use. The other side of this coin, though, is that cheap CB gear can often be modified for legal use by hams on 10M.

* 6M

• This is the "magic band" that lies between HF and VHF. Although there are a few 6M repeaters in the country and people will sometimes come back to you if you call on 52.525 with an FM transmitter, what makes 6M cool is that occasionally there is DX propagation. During the solar maximum, conventional skip is possible but at other times there is occasional sporadic-E and tropospheric ducting. The majority of 6M DXers use SSB, but even an old Army field radio tuned to the FM calling frequency can bag interesting QSOs. Because you never know what 6M will do, there is an active set of beacons on the band that you can leave a receiver tuned to so as to alert you to band openings.

* 2M

• This has become the de-facto local communications band. There are very few parts of the country out of range of a 2M repeater. While tropospheric ducting can allow 2M DX and sporadic-E propagation has been seen on this band, these are more the realm of a small group of dedicated obsessives than regular propagation modes for daily use. 2M is very popular both for direct simplex communication and for repeater use. However, you should know that the repeater culture varies greatly from place to place; listen to the repeater for a while before jumping in. 2M propagation is almost entirely line of sight.

* 1.25m (220)

• 220 is another VHF band with line of sight propagation. It is a strange band without a lot of activity, and because of that in the late 1980s, United Parcel Service petitioned the FCC for the 220-222 Mhz section of the band which was granted to them. Although UPS never used it, it was never returned to amateur use, so hams currently have the 220-225 MHz sections, and in addition an odd chunk at 219-220 Mhz which is allocated only for "fixed point to point digital messaging services," ie. packet radio. Some repeaters exist on 220 but it is very much an underutilized band.

* 70cm (440)

• This UHF band can give better propagation in urban areas than 2M, because of reduced problems with multipath (where multiple reflections from the same source appear at the receiver at different times). Because of congestion on the 2M band (especially on repeaters) there have been many people moving to 440.

* 33 cm (902)

• Much of this band is shared with ISM devices, so you may encounter baby monitors and security cameras appearing alongside ham users. Some repeaters on this band exist. Propagation characteristics are much more touchy than on 2M and 440, with sometimes a six-inch shift in position enough to change reception characteristics due to multipath.

* 13 cm (2300-2310 and 2390-2450)

• Yes, if you noticed, this band overlaps with the ISM band used for WiFi and many other things. This means that you can use existing WiFi hardware and the like in this band. But it's not quite that simple. If you use 2.4 GHz as an ism band you can use encryption and arbitrary ID and ISM-band power limits. BUT, if you want to use higher power as allowed for ham use, you have to use your callsign and no encryption. It's the same frequency but under a different allocation paragraph in the regs. However, hams have done line of sight between mountaintops using off the shelf WiFi hardware and high gain antennas, for hops longer than 30 miles, so do not despair that the band is not useful.

* The Other Microwave Bands

• I don't know anything about the higher microwave bands, but there are a lot of them, from 3300 Mhz on up to an authorized allocation at 241-250 GHz. Some of these bands have frequencies shared with ISM users, some of them are on frequencies with substantial attenuation in air. Please add something useful to this.

http://www.arrl.org/graphical-frequency-allocations