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A nightmare for HAM Radio operators: The “Russian Woodpecker”

During the 1970s and 80s Russia deployed their Over-the-Horizon Radar (OTHR) which ultimately became known as the “Russian Woodpecker” to HAM Radio enthusiasts worldwide. Why that moniker? Well the signal emitted a sound pattern of its transmitted pulses at HF frequencies that was heard on worldwide shortwave radios to the annoyance of HAM operators. You can hear the sound of the Woodpecker signal on YouTube here.

Shown here is the Duga-1 RADAR array within the Chernobyl Exclusion Zone. On the right side can be seen an array of pairs of cylindrical/conical cages; these are the driven elements, fed at the facing points with a form of ladder line suspended from stand-off platforms at the top right of the image. A backplane axel reflector of small wires is seen left of center, most clearly at the bottom of the image. (By Necator - the English language Wikipedia (log), Public Domain)

Shown here is the Duga-1 RADAR array within the Chernobyl Exclusion Zone. On the right side can be seen an array of pairs of cylindrical/conical cages; these are the driven elements, fed at the facing points with a form of ladder line suspended from stand-off platforms at the top right of the image. A backplane axel reflector of small wires is seen left of center, most clearly at the bottom of the image. (By Necator – the English language Wikipedia (log), Public Domain)

This RADAR system was an early warning anti-ballistic missile radar system that was put into operation in late 1971—-based in Chernobyl. This RADAR’s pulses were hopping between four broadcast time windows at four distinct frequencies: 16450, 16490, 16570 and 16390 kHz—one for each window.

In the “static” mode (Static information does not require a high refresh rate; that is Name, Call sign, Tonnage, Destination, ETA do not change and are forwarded), each pulse had a bandwidth of 40 kHz, and a length of 3 to 6 ms. The signal was typically broadcast for 10, 16 and 20 times per second and then followed by a 72 ms silent period.

In the “dynamic” mode (Dynamic information, is position, course, speed, heading, ROT, etc. is changing constantly), four frequencies that could have also been used on other areas of the HF band (8070, 8230, 8310 and 8260 kHz, for example) were all transmitted sequentially in each and every time window in intervals of 6 ms.

In the highly used 10 Hz mode, where the four frequencies were transmitted every 100 ms, the duration of each distinct frequency’s transmission window was 7 ms, thus resulting in a 27 ms continuous broadcast followed by 72 ms of silence, all adding up to 100 ms. There were a number of transmission hopping and timing techniques that were used by the Soviets to avoid jamming of their transmit frequencies as well as to prevent spoofing of the received echoes. It was the power and range of this system that was a ‘thorn in the side’ to all shortwave listeners and amateur and commercial HF operators worldwide.

See my original article on this subject in the Spectrum Monitor.

If you are a HAM operator or a RADAR expert, please share your thoughts on this subject with our audience by registering on Planet Analog and commenting below

6 comments on “A nightmare for HAM Radio operators: The “Russian Woodpecker”

  1. Jean-Luc.Suchail
    February 22, 2017

    I remember this stuff, in France it was called “The Machine Gun”….

    Was a nightmare on HF bands.

  2. KB6NU
    February 22, 2017

    Great article, but the name of our hobby is not “HAM” or “HAM radio.” It's not an acronym for anything. It's simply “ham radio” or “amateur radio.” 

    73,   < --ham radio lingo for "best regards"

    Dan Romanchik, KB6NU

  3. Steve Taranovich
    February 22, 2017

    Thanks for your feedback Dan. Any idea where the 'ham radio' nomenclature came from?

  4. Andy_I
    February 22, 2017

    It's been said that the origins of “ham” and “ham radio” are unknown, or that it dates back to pre-radio, with the wired telegraph.

    The ARRL has a story for it, which may or may not be true.  Ham was defined as “a poor oprator”, also called a “plug”, in “The Telegraph Instructor” (1901) by George M. Dodge.  In the early days with spark-gap transmitters, an amateur's radio signal could blanket the whole band — similar to the Russian Woodpecker.  Commercial radio operators started using the term “ham” to referr to amateur radio stations with huge signals that could hog the spectrum.  Or so the ARRL claims.

    “Plug” meant “a telegraph operator, who lacks ability.”

    “Ham” was in use already before 1901, before Marconi's trans-Atlantic transmission, when there were hardly any radio operators, amateur or otherwise.  So I wonder if the term “ham” was used not to refer to the interfering radio signals, but to the fact that some of those amateur radio people were new with Morse Code and they were sloppy at it.

    In any event, amateur radio operators didn't know “ham” was derogatory, and started using it themselves.

  5. Andy_I
    February 22, 2017

    I was not a ham back then, but was an occasional SWL – shortwave listener.  I do indeed remember hearing the Woodpecker and some of the talk about it.  When their signal was coming in, SWLing was just about useless.

    There were other, jamming signals in use back then, to impede reception of certain shortwave broadcasts.  Along with lots of other coded signals.  So it didn't surprise me to find another unpleasant signal on the bands.  What was annoying about the Russian Woodpecker was how much RF spectrum it took up, and my radio didn't have a “noise blanker” which might have helped.

    In the end maybe the “Russian Woodpecker” wasn't Russian at all.  Soviet, yes.  Geographically, Ukranian, perhaps.  Although there were Duga sites in other Soviet republics, so who knows which ones we were hearing?

  6. RadioGraybeard
    February 24, 2017

    I was an active ham in those days, and I remember them showing up in amateur bands all over HF.  I tended to hang out on the 15m band, 21.000 – 21.450, but I'd hear them most at the bottom end where Morse code operators were allocated. 

    Someone decided (or heard) that it was pulse radar and decided the obvious way to overcome it was to transmit back at it with a similar pulse rate.  There would be no information content, but you'd probably be much louder than the return.  It was pretty simple really: turn up the speed on your keyer until it sounded like the same pulse rate and transmit back.  If you could peak their signal and your return by rotating your beam, all the better. 

    I remember once hearing the Woodpecker stop, as if the operators were saying to each other “what the heck was that??”, then they'd start again and the self-annointed jammers would start.  They'd move around the band the jammers would follow them.  It seems they eventually chased the Woodpecker away, because they either changed frequencies or modes or something. 

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