Don’t Believe the Hype

The capabilities and performance of the Russian Army’s Repellent-1 may have been exaggerated by the system’s manufacturer. It has shown poor performance in the past regarding its ability to detect and jam UAVs.

The performance of the Russian Army’s Repellent-1 counter-UAV system maybe greatly exaggerated according to Armada’s latest analysis.

Pity the poor Russian Electronic Warfare (EW) cadre. Things do not seem to be going well. According to oryxspioenkop.com Russian forces have lost eight EW systems in Ukraine since the war began. To exacerbate matters, Ukrainian forces killed Major General Andrei Simonov in early May. Maj. Gen. Simonov reportedly commanded the EW elements of the Russian Army’s 2nd Guards Combined Arms Army (CAA). The 2nd Guards CAA is thought to receive operational-level EW support from the 18th Independent EW Brigade. Maj. Gen. Simonov died near Izyum, 110 kilometres/km (68 miles) southeast of Kharkiv, eastern Ukraine. He is the ninth senior Russian Army officer killed by Ukrainian forces since the war began on 24th February.

amr_takeover_right

There has been no let-up in the bad news for Russian EW cadres. Ukrainian news sources revealed that Ukrainian Army artillery had destroyed a Russian Army Repellent-1 electronic warfare system in late April. This was deployed in the vicinity of Kherson, southern Ukraine. According to uawardata.com, this is the 49th CAA’s area of operations.

Armada has seen official documents detailing the Repellent-1’s capabilities. We used MASS’ Electronic Warfare Mission Support Tool (EWMST) to get an idea of the system’s performance. The Repellent-1 detects Uninhabited Aerial Vehicles (UAVs) via their Radio Frequency (RF) links. These connect the aircraft to its Ground Control Station (GCS). This allows commands to be sent up to the UAV and imagery and other information gathered by the UAV to be shared. These links typically use frequencies of 2.4GHz and 5.8GHz. UAVs also depend on RF links to receive GNSS (Global Navigation Satellite System) navigation signals on frequencies of 1.1GHz to 1.6GHz. Frequencies of circa 900MHz up to 5.8GHz are utilised to transmit video imagery to the GCS or other users on the ground. Theoretically, all these links can be engaged with the Repellent-1’s jamming system.

Literature seen by Armada says that the Repellent-1 can detect and jam signals on frequencies of 200 megahertz/MHz to six gigahertz/GHz with between 200 watts/W and one kilowatt of jamming power. The literature claims a UAV’s RF signals can be attacked at ranges of up to 19 nautical miles/nm (35 kilometres/km). Up to twelve UAVs can be jammed simultaneously. Meanwhile, the documentation says it takes the Repellent-1 up to 25 seconds to detect and jam a UAV.

Rock the Party

Do these claims stand up to scrutiny? Using the EWMST Armada ran a hypothetical scenario. We positioned a Repellent-1 to the west of Kherson, southern Ukraine providing coverage over Russia’s western frontlines. In our scenario, we placed the Repellent-1 at Kherson International Airport. Local sources say that this is the base for the Russian Army’s 127th Separate Reconnaissance Brigade as of early May. This latter unit is part of the 22nd Army Corps.

For the scenario we assumed that the Repellent-1’s 14 metre/m (46 feet/ft) antenna is fully extended. The antenna is positioned on a Kamaz-6350 truck which is circa three metres (ten feet) tall. This gives the Repellent-1’s antenna a total height of 17m (56ft). Technically, the Repellent-1 should be able to detect and jam the RF signals of a UAV flying at 30,000ft (9,144m) at ranges of up to 222nm (411km). In reality the Repellent-1’s jamming range depends on the frequencies it is targeting, the jammer’s power  and local topography. For example, buildings and elevated terrain can obstruct a jamming signal’s line-of-sight to its target.

We placed a UAV at 25,000ft (7,620m) altitude, 15.7nm (29.1km) northwest of the Repellent-1. The UAV’s pilot and ground control station were 40km (22nm) from the jammer. The Repellent-1  transmitted 1000W jamming signals on frequencies of between 200MHz to six gigahertz. The UAV and the GCS were linked with an unencrypted 2.4GHz signal.

According to our analysis at best there is a ten percent to 50 percent probability that the GCS-UAV RF link will be adversely affected by the jamming. In Figure-1 the area where jamming efficacy is likely to be between ten and 50 percent is depicted in red. The area where jamming efficacy is between 90 and 100 percent is shown in green. At most, the jammer can engage RF signals with 90 to 100 percent efficacy at ranges averaging 12 nautical miles (23km).

When jamming a 2.4GHz RF link connecting a UAV to its GCS with a 1000W signal, the Repellent-1 in our scenario appears unable to achieve a range exceeding twelve nautical miles.

Figure-2 shows that if the Repellent-1 reduces its jamming power to 200W these ranges diminish further. On average, the system will be lucky to achieve seven nautical miles (14km) with 90 to 100 percent efficacy. This does not mean the UAV-GCS RF link will be unaffected. Nonetheless, the link should still enjoy between 50 and 90 percent integrity.

The engagement ranges of the Repellent-1 may diminish further when transmitting 200W of jamming power.

Although our scenario employs omni-directional jamming, matters scarcely improve if the jamming is focused in one direction. A 200W signal on a 320-degree bearing with a 30-degree beamwidth can reach at best eight nautical miles (15km) with 90 to 100 percent efficacy as depicted in Figure-3. Taking the power up to 1000W improves things a little but still only gives a range of just over twelve nautical miles as shown in Figure-4.

Directional jamming seems to scarcely improve the Repellent-1’s performance. A 200W jamming signal with a 30-degree beamwidth will achieve a range of eight nautical miles.
Increasing a jamming signal’s power to 1000W does improve the Repellent-1’s directional jamming performance but not by much. At best a jamming range just over twelve nautical miles is achievable.

Turn up the Radio

What does this scenario tell us about the Repellent-1 and Russian Army EW capabilities writ large? In our scenario the Repellent-1 manufacturer’s claim of a 35km UAV jamming range seem exaggerated. Both the UAV and the GCS were outside the worst of the Repellent-1’s jamming even when the latter was at full power. Indeed jamming power seem to be the issue. When we gave the Repellent-1 a hypothetical nine kilowatts of power it could easily attack the UAV-GCS link. In fact, this jamming signal reached out to 22.7nm (40km).

If the manufacturer is exaggerating the Repellent-1’s capabilities, one wonders if the capabilities of other Russian Army EW systems are not similarly overplayed? If this is the case, it may explain why the apparent under performance of Russian Army EW systems has become a hallmark of this conflict.

Why the capabilities of Russia’s EW systems may be overstated is something of a mystery. Western manufacturers tend to publicly ‘down-tune’ their systems’ performance compared to what is actually possible. From a tactical point of view this makes sense. It helps to keep potential enemies guessing.

Is the manufacturer hyping the Repellent-1’s capabilities in the hope of winning export sales? Concerns regarding the Repellent-1’s performance have been expressed in the past. In 2017, Armenia procured a Repellent-1 system which proved powerless against UAVs used by the Azeri armed forces.

The Repellent-1’s apparent shortcomings can only be good news for the Ukrainian armed forces. It may mean that Ukrainian UAVs can get closer to Russian force dispositions when collecting imagery. Moreover, one EW system out of the fight is one less EW system to worry about.

by Dr. Thomas Withington