Wednesday, August 28, 2019

Low frequency radio listening

Lower in frequency than the AM broadcast band is the low frequency (or long wave) band. The main use for this part of the spectrum in Australia is aircraft navigation beacons (NDBs), which transmit in the 200 to 480 kHz range. These beacons transmit their callsign (which is a two or three letter abbreviation of their location) in slow morse code, with a few transmitting voice weather information in AM. Hundreds of beacons are active; during a recent evening listening test in suburban Melbourne, some eighty were heard, some as far away as Kalgoorlie and Mt Isa, with just a small ferrite rod loopstick as an antenna. More recently some have shut down. However there are some new users of the LF and MF bands, with radio amateurs recently gaining allocations around 135 and 472 kHz.

These videos show reception of scans of NDB and amateur stations on frequencies below 500kHz. I'm using a home-made upconverter that shifts LF signals to a segment above 4 MHz. This converter contains a ferrite rod which operates as a directional receiving antenna. The videos include reception of amateurs and NDB beacons, some of which have ceased transmitting.

PS: Enjoy reading? Consider this selection of amateur radio books I have written. They are available in ebook or paperback. 


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