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WW2 Signals Spectrum – A Quick Survey

ww2 signals spectrum

You would have enjoyed being a shortwave listener during the war. WW2 signals spectrum was absolutely hopping over its full range. 

Radio became central to command and control of all military forces. The spectrum was used for short tactical and long range communications over huge areas. Since this was a war of moving rather than static forces, flexibility was imperative. Because of wireless intercepts, the benefits real-time control were offset by only short term security.

So here is a brief survey of what you could expect to hear on the radio bands between 1939-1945. In addition to military communications, domestic and regional broadcasting continued on low and medium waves, as did international news and propaganda on shortwaves.

WW2 Signals Spectrum – Below 2 MHz (VLF, LF, MF)

Low and medium waves (LF, MF) provide reliable communication up to 1,000 km by ground wave, especially over water. High power is required to overcome atmospheric noise, especially in tropical areas. Good skywaves can span oceans. Very long waves (VLF) have the added benefit of penetrating into salt water for a short distance.

Navies used high power LF to communicate with ships at 100 – 500 kHz. Germany used LF for naval and air force homing and navigation, as well as some high power VLF for sending instructions to submarines, such as Goliath. Also, LF was used by armored forces for regimental signals. Most transmissions were Morse.

WW2 Signals Spectrum – 2 to 12 MHz (Lower HF)

These frequencies were the work horse for military communications over all distances, especially at night and during winter when absorption is lower. Both ground and sky waves were used, and “skip zones” were avoided by NVIS arrangements (near vertical incidence skywaves).

All forms of modulation were used including W/T (wireless telegraphy), R/T (radio telephony) and data. U-boats used 10 and 12 MHz for long distance communication at night. Luftwaffe did long range navigation, and artillery and infantry ran low power communications. Some V1 missiles sent telemetry on these frequencies.

The Allies ran AM infantry man-pack,  walkie talkes and mobile rigs on 5 – 9 MHz. British tanks communicated over 2-6 MHz in the early stages. During the Battle of Britain, Spitfires used 5 MHz for air-to-air and air-to-ground. Interestingly, during this period, German fighters used R/T while bombers used W/T. Even though they were on similar frequencies, they could not communicate with each other during the air battles.

Long and short distance communication by warships was common in 2-5 MHz. LORAN navigation showed up at 2 and 11 MHz.

This was also the spectrum used by most spy suitcase radios.

WW2 Signals Spectrum – 12 to 25 MHz (Upper HF)

During sunspot highs, these frequencies are mainly long distance using skywaves. But surprisingly, both sides tried a lot of short range communication here. The venerable Sherman tank did its R/T in upper HF, as did much of German armor. Wehrmacht short range infantry and close support showed up at 20 MHz. Both Japanese and German naval forces did long distance around 16 MHz.

But perhaps most interesting was Britain’s Chain Home radar system, which blanketed frequencies between 20-30 MHz.

WW2 Signals Spectrum – 25 to 75 MHz (Lower VHF)

Generally, this band is line-of-sight over distances up to 100 km. Some skip can occur during sunspot highs, but mostly the cause of longer distances is ducting.

Americans were fast with the development of FM tactical communications, especially to mitigate ignition noise in vehicles. FM backpacks used 28-52 and 40-48 MHz. Popular vehicular FM covered 20-28 MHz. Similar frequency use occurred with German tanks and low power infantry backpacks, although more on AM. Navy and U-Boats did short range voice. American navy used this band for Talk Between Ships (tactical).

Sharing this band was navigation. German bombing beams ran on 30-35 and 60 Mhz. Meanwhile, the Allies GEE Bomber Navigation system covered 20-85 MHz.

WW2 Signals Spectrum – 75 Mhz and up (VHF, UHF)

By the end of the Battle of Britain, the RAF moved to 100-124 Mhz. British ground forces took on low power R/T on 229-241 MHz. The Germans used UHF for military phone networks and infantry truck mounted voice and teletype.

But mostly, it was radar. Early US radar operated on 105 and 205 MHz. (That Pearl Harbor radar station in the movie was was the SCR-270 on 105 Mhz.) These frequencies were also used for gun control. Chain Home Low operated at 200 MHz during Battle of Britain. Early German radar was also on these frequencies, while Soviets used 75 MHz. Oboe navigational transponders were on 200 MHz.

Now, have fun watching how some of this radio equipment was built and used.

 

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