Really Low Frequency Operating

The world below 500 kHz (The wavelength is 1500 meters or just about a mile) has a number of interesting listening and communications opportunities with possibly more to come. The FCC has recently issued experimental licenses to a small group of hams to evaluate low frequency operation.

This portion of the radio spectrum is known as longwave and was originally popularized by Marconi when he found that consistent communications were possible 24 hours a day at these frequencies, provided that truly humongous antennas and extremely high power transmitters were used. In the early 1920's, hams found that they could make worldwide contacts using much lower power at higher frequencies, the short waves. This soon led to others, including Marconi, moving to higher frequencies for communications. The trick was to understand radio propagation, using the right frequency at the right time of day. So, what's on longwave today?

1. There is a European longwave AM broadcast band at 148-280 kHz and some of these stations can be heard in the US under favorable conditions.

2.Virtually every airport in the world has a non-directional beacon operating from 190-530 kHz. They continually transmit their call letters in slow Morse code and not only provide excellent code practice opportunities but also provide challenging SWL'ing, since several are located at almost any frequency and a selective ear is required to identify them.

3. The FCC allows experimentation on a band from 160-190 kHz under their Part 15 rules with strict limitations, namely, 1 Watt input and a 15M total antenna length. Most of the low frequency experimental radio stations (LowFERS) operate as beacons, continually repeating their call letters in Morse code much like the aircraft NDBs mentioned earlier.

I operate beacon "RB" at 186.92 kHz and it has ben heard by people as far away as northern Minnesota. The antenna is a 31 foot vertical with a 25 foot diameter top hat. It is series fed with an inductor and has 32 buried radials ranging from 40 to 150 feet in length, with 16 of them terminated with 5 foot ground rods.

.4. Time Standard Stations: WWVB is the most well-known one and operates on 60 kHz. It is used in the "Atomic Clocks" you may have seen advertised that provide continually updated accurate time.

5. The ARRL has recently petitioned the FCC for ham radio privileges at 135.7 to 137.8 kHz and 160 to 190 kHz. The first band is already used by many hams in many European countries and the second is where LowFER operation currently takes place. If this petition is accepted, operation should be possible over longer distances more reliably because the antenna restrictions will be removed and higher power will be permitted.

6. The Longwave Club of America has a website that is chock full of useful and interesting longwave info.

Return to Table of Contents