Medium Wave is an exciting and challenging band for the DX enthusiast. It is often the first DX experience that many have, because it does not require expensive equipment. In fact, several low budget radios have been marketed just for this purpose. Even radios that were not intended to receive distant stations are frequently useful. Of course, the communications receivers, loop antennas, & very long wires will produce the greatest results, but many DXers have achieved many great loggings using modest equipment. Although this series of articles may convey useful information to those using the better equipment, the primary focus will be on the new DXer, those most likely to be using the Superadios & Radio Shack TRF's.I frequently receive E-mail from DXers unfamiliar with DX or medium wave, wanting information on what can be heard & what kind of equipment is required. Hopefully I will be answer most, if not all of those questions. Since I have a worldwide audience I will warn you that these articles are directed at the North American DXer, and are written from the perspective of a midwesterner who is strictly a domestic DXer. I will attempt to get someone knowledgeable about international DX to write a complimentary article sometime in the future.
Traditionally the medium wave band covered roughly 530-1610. Recent developments have resulted in the upper limit being extended to 1710 kHz. In North America, stations are spaced at 10 kHz increments, with all stations on frequencies ending in zeros (such as 610, 990, 1500, etc). In most other parts of the world, station spacing is every 9 kHz. In a few areas, particularily South America & the Carribean, there are some stations with 4 or 5 kHz spacing (these are the exception, most use 10 kHz spacing). In North America, generally, the powers are restricted to 50 kilowatts. There are a handful of stations in Mexico & the Carribean with higher power. In other parts of the world powers are significantly higher, with some as high as 2 megawatts.
For most DXers in North America the majority of the stations received will be from Canada and the United States (this may not be true for those in the far southern sections of the U.S. where Cuban, Mexican, South American, & Carribean stations are often dominants). The frequencies in these two countries are divided into three classifications: clear channels, regional channels, and local channels. Clear channel stations operate with a power maximum of 50000 watts, but most will have lower powers. The regional channels have, until recently, been restricted to 5000 watts in the U.S. & 50,000 watts in Canada. Recently the FCC has allowed a handful of stations to operate with significantly higher power, with sophisticated directional antennas. The local channel stations operate with a power maximum of 1000 watts nondirectional, except for a few Canadians which have powers as high as 10000 watts, using directional antennas.
The clear channels, as the name implies, used to be frequencies a with very limited number of high powered stations, capable of covering large geographic areas. Until recently some of the frequencies only had one station in all of North America. In recent years the clear channels have undergone significant change, resulting in an increase in the number of stations on each frequency. There are 3 types of clear channels. The 1A clears contain a protected station. This station nearly always operates with 50000 watts using a nondirectional. A couple of stations on one of the coasts use directional antennas to increase coverage area (an example is WBZ-1030 Boston, which throws all of its power west). No fulltime station may be within 750 miles of a 1A clear, and stations beyond 750 miles must use a directional antenna pattern designed to prevent interference in this protected zone. The class 1A clears are some of the most famous stations in the U.S, WABC, WLS, WGN, WWL, WSM, WSB, KFI, etc. Class 1B clear channels contain two 50000 watt stations, with directional antennas reducing interference with each other. These 1B clears do not have a protected area. An example of a class 1B clear is 1110, with KFAB from Omaha, NE & WBT from Charlotte, NC. Class 2 clear channels are primarily frequencies allocated as clear channels Mexico or the Bahamas. These generally contain numerous stations, many operating with very low powers. There will be a few higher powered stations with highly directional antennas. The class 1A clear channels are: 640-680, 700, 720, 740-780, 810-850, 870-890, 1020-1040, 1060, 1100, 1120, 1140, 1160, 1180, 1210-1210. Class 1B clears are: 690, 710, 860, 900, 1000-1010, 1070-1090, 1170, 1190, 1500-1520, 1560. Class 2 clears are: 540, 730, 800, 940, 990, 1050, 1130, 1220, 1540, 1570-1580.
Regional channels contain considerably more stations than do the clears. Nearly all full power regional channel stations use directional antennas. On most regional channels there are several widely spaced dominant stations. These will usually be 5000 watts with a less restrictive directional antenna pattern (a few are nondirectional). Other nearby stations will be lower power or use a highly directional antenna engineered to reduce interference to the dominant stations. Frequently directional patterns on regional channels are quite sophisticated, because they are designed to reduce interference to several stations. The same action that resulted in the breaking up of the clear channels has also had an effect on the regionals. Today, many stations that were formerly daytime only operations are now broadcasting 24 hours a day, with very low powers. Suprisingly, many of these get ouit real good, even with 20 or 30 watts in some cases. Nearly all of these low power transmissions are made with a nondirectional antenna. The regional channel frequencies are: 550-630, 790, 910-930, 950-980, 1150, 1250-1330, 1350-1390, 1410-1440, 1460-1480, 1590-1600.
Easily the most interesting and challenging frequencies are the local channels. These channels contain over 150 stations, nearly all 1000 watts nondirectional fulltime. A few Canadians have higher power using highly directional antennas. Local channels have absolutely no guarantee of interference free reception outside their imediate listening area. In the larger cities they will be inaudible in some areas of their market. Listeners at 10 or more miles from the transmitter will have interference problems in many cases. When you tune to an open local channel, it will sound like a mess. There are so many stations coming in that they can cancel each other out. Thus, getting IDs can be a challenge. Frequently stations will fade up for very brief periods. It is unsual to have a single station totally dominate the frequency. Because of these conditions, the local channels have been nicknamed the graveyard channels by medium wave DXers. There are only six local channel frequencies: 1230, 1240, 1340, 1400, 1450, 1490.
A new area of interest to the medium wave DXer is the so called expanded band. Several years ago a new international treaty extended the range of the AM broadcast band to 1710 kHz.Currently there are only 2 North American operating in the Expanded Band: KXBT-1640 (ex-1630) Vallejo, CA & WJDM-1530 Elizabeth, NJ. Also found in this frequency range are many traveller's information stations (TIS), called this because originally they served as information stations for communters & tourists. Today they are used not only for road information, but also as community information stations by municipalities. There are even a few low powered broadcasters here. Generally TIS stations are restricted to 10 watts or less. An exception are the two stations at the Dallas-Fort Worth Airport on 1640 & 1680. Both of these are 60 watts & have been logged throughout North America. Also found in this band are the medfer beacons. These are extremely low powered stations run by expiramenters who are usually ham operators. These stations are limited to 1/10th of a watt. They mostly run continuous MOrse Code IDs, and can be heard over hundreds of miles in good conditions.Activity in the expanded band should increase in the near future. The FCC has released a list of stations eligible to move here. Exactly when this will take place is anybody's guess. To view the list, click here: NEW EXPANDED BAND LIST . All of the new operations in the expanded band will run 10000 watts days & 1000 watts nights, nondirectional. This should make for some very interesting DX.
Be watching for Part 2 of this article series, which will discuss equipment.
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