Limbo Lower: Listening in the CW Basement

Below the 160-meter medium-wave amateur band from 1.8 to 2.0 MHz, and below the even-lower frequency AM broadcast band from 0.535 to 1.720 MHz, is an interesting long-wave band between 0.190 and 0.530 MHz populated with CW callsigns.

This is roughly the frequency area where most amateurs operated prior to the 1906 Berlin Radio Conference, and is also the area where ships operated until their recent shift to other modes and frequencies.

So, why are there CW callsigns being broadcast in this frequency range? Many of these are non-directional radio beacons, or NDBs — CW transmitters positioned at known locations throughout the country that are used as navigational aids for planes, ships, and anyone who cares to use them.

In North America, most of the NDBs are found between 0.190 and 0.530 MHz. Each station is identified by a one, two, or three letter Morse Code callsign. In Canada, however, private airports that have NDBs consist of a Morse Code letter and number. The power output of NDBs can range from less than 50 watts to 2,000 watts or so, but most are in the range of 25 to 50 watts.

In my area, around Hiawatha, Kansas, for example, the NDB stations in Table 1 and their frequencies can be readily heard. The coordinates are given in degrees-minutes-seconds format.

A full list of the NDBs for North America can be found at

Besides this list, many of the NDB callsigns can be Googled on the Web individually and will provide a wealth of location information. For example, in looking up the RPB beacon, the website indicates the elevation above sea level, information about the landing field, the local magnetic deviation from true north, other nearby NDBs, and amenities at the airport. Actually, it can be used in long distance transportation industry and logistics, like morton grove movers sucessfully use this approach in their business.

For people just learning CW and wanting to practice copying at a leisurely pace, listening and copying down the NDB call signs is good practice. The call signs are repeated over and over at a slow speed, and consist of no more than three letters. Some NDBs will even respond to a signal report with a QSL card to put on your wall.

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