“Waterfalls” of jamming frequencies featured in this program.*

Radio frequency jamming is the intentional disruption of a radio signal by the broadcast of a stronger signal on a similar frequency.  A transmitter utilizing the same frequency and modulation as another signal – provided it is powerful enough – can override the reception of that signal.  Rather than squelching the broadcast at its source, jamming can prevent the reception of a radio frequency within a particular geographic region.  

Historically, jamming has been a technical approach to political problems. Jamming has been a facet of electronic warfare since Wold War II.  The Cold War radio arms race saw the transmitter power of Radio Free Europe increase to one million watts to counteract Soviet jamming.  Iran, North Korea, and China routinely jam all international radio signals into their countries.  Radio Ethiopia and Radio Eritrea chase each other across the dial, each seeking to jam the others’ transmission while simultaneously changing broadcast frequencies in order to avoid being jammed.  

But radio waves are not just used to transmit the spoken word.  In this age of wireless data, the RF spectrum is filled with electromagnetic information. Discrete packets of coded data, inherently clandestine, are transmitted via radio, and particular sonic signatures are being created to corrupt and obscure these transmissions.

This edition of Special Collection will focus on the jamming of radio data, rather than radio sound.  Random noise, pulse generators, stepped tones, warblers, randomly keyed continuous waves, bubbles, DMTF signals, and frequency sweeps populate this empire of noise.

*For more information on waterfalls, consult Special Collections program Chasing Waterfalls: WebSDR from December 2016.

Special Collections thanks Rimantas Pleikys, former Minister for Communications and Informatics of Lithuania and author of the 2006 book Jamming, which provided heavy background for the ideas that germinated this program.