Serge Sklyarenko says his organization,\u00a0American Ukrainian Aid Foundation<\/a>, based in New York, is supplying Ukrainian intelligence with a number of the versatile SDR radio kits.<\/p>\n \u201cThe beauty of them is they are software defined, meaning they can be reprogrammed in the field to suit a multitude of use cases,\u201d Sklyarenko told me.<\/p>\n In a traditional radio set, the signal from an antenna is processed by dedicated hardware \u2013 amplifiers, filters, modulator\/demodulators and other components. This means that each radio set is dedicated to one particular type of radio signal, whether it is a 5G cellphone, AM radio, digital television or WiFi. In Software Defined Radio, the only dedicated hardware is the antenna. All the signal processing is carried out digitally with a computer. Simply by changing the programming, an SDR can extract the signal for cellphone, radio, Bluetooth, or any other defined waveform. One device can do everything.<\/p>\n While simple in theory, SDR initially required a tremendous amount of computing power, and it took a\u00a0push by DARPA in the 2010s<\/a>\u00a0to make the technology viable. DARPA has continued to pour\u00a0research funds into SDR development<\/a>\u00a0including an\u00a0advanced system-on-a-chip<\/a>\u00a0demonstrated by Raytheon last year using standard IntelINTC<\/a>\u00a0+2.3%<\/span><\/a>\u00a0hardware.<\/p>\n Now open-source SDR kits are available on the consumer market, and Ukraine is putting them to good use.<\/p>\n \u201cThe SDRs are a basic coherently operated, five-channel receiver,\u201d says Sklyarenko. \u201cWhile signals analysis is generally quite classified we sent these radios for the basic purpose of \u2018fox hunting\u2019 or direction finding. Essentially they are listening for spurious radio transmissions.\u201d<\/p>\n A\u00a0fox hunt<\/a>\u00a0is a contest between ham radio operators to locate a hidden radio transmitter, usually just for fun. But in this case the game is deadly serious.<\/p>\n Analog direction finding is essentially a matter of rotating a directional antenna to find the strongest signal; by using with several antennas, or moving to different locations, the source can be located by triangulation.\u00a0Digital direction finding<\/a>\u00a0is more sophisticated and uses the difference in phase between the signal across multiple channels.<\/p>\n Previously, this type of radio direction finding gear was bulky and could cost tens of thousands of dollars. The new technology shrinks it to palmtop size, and, with\u00a0open-source SDR software<\/a>\u00a0and cheap processors like the\u00a0Raspberry Pi<\/a>\u00a0brings cost down to a few hundred.<\/p>\n Since early on in the war, Ukrainian volunteers have been able to listen in to much of the Russian military radio traffic, due to Russia\u2019s\u00a0lack of modern radio equipment<\/a>, and even\u00a0jamming them<\/a>\u00a0by transmitting raucous heavy metal on the same frequency. The fox hunting SDR kits will allow Ukrainian operators to pinpoint Russian transmissions and target them with mortars, artillery, HIMARS or other weapons.<\/p>\n In particular, the technology can locate the Chinese-made DJI quadcopters used by Russian forces as well as their operators on the ground.<\/p>\n \u201cIt is very public knowledge than you can use SDRs to locate DJIs,\u201d says Sklyarenko.<\/p>\n The SDR receivers could locate all radio emitters across a wide area, including for example air defense radars and Russian electronic warfare systems used to jam GPS. Russia has a\u00a0wide variety of such systems<\/a>. For more distant sources, this would require a network of SDRs linked together to form a large-scale sensor net. This concept was already explored in DARPA\u2019s\u00a0RadioMap<\/a>\u00a0project. Ukraine may be the first nation to implement this concept on a large scale, thanks to abdundant, low-cost receivers.<\/p>\n \u201cIt would be great to cover the entire country with SDRs,\u201d says Sklyarenko.<\/p>\n The receivers are so small they can even be carried on drones. Signals intelligence is useful not just for locating individual transmitters, but can identify the position of units from their radio traffic, and spot movement as a headquarters deploy into an area.<\/p>\n While radio intercepts can determine location, the most important Russian military communications are encrypted, making them impossible to break into. That might change.<\/p>\n \u201cWe imagine SDRs could be used for a lot more interesting applications, for example intercepting transmissions for decryption on supercomputers. But they won\u2019t tell us,\u201d says Sklyarenko. \u201cAll we know is that these are in high demand, and we are happy to help sending them.\u201d<\/p>\n![\"\"](\"https:\/\/www.fie.undef.edu.ar\/ceptm\/wp-content\/uploads\/2022\/11\/960x0-1.jpg\")