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FenrisDEFENCE · FD-0001
SystemsMIMIR
IN PRODUCTION

Mimir

C-UAS · DETECTIONHandheld passive RF detector

A handheld receiver that finds FPV drones by the video they are already transmitting — and then puts that video on its own screen. You do not just learn that something is flying. You see what it sees.

BANDS
1.3 · 3.3 · 5.8
SWEEP
4—8 S
RANGE
UP TO 4 KM
EMISSION
NONE

Knowing a drone is overhead is half an answer. MIMIR gives the other half. Every FPV aircraft has to send its picture back to whoever is flying it, and that transmission is the thing MIMIR listens for. It sweeps three bands at once, tells you the moment it hears one, and — when the signal is strong enough — decodes the feed and shows it to you. So you can see whether your position is in frame, what the operator is circling back to, and where the aircraft is looking right now. It transmits nothing itself, which means nobody learns you are carrying it.

Design intent
0101 / 06

See what the drone sees

Decoding the downlink turns a contact into intelligence. An alert tells you something is up there. The picture tells you whether it has found you, what it keeps returning to, and which way it is pointed.

0202 / 06

Listening is not transmitting

A passive receiver has no emission to locate. Nothing about carrying MIMIR tells the other side you are there — which is not true of a jammer, and is the whole reason to reach for this first.

0303 / 06

Three bands, in parallel

1.3, 3.3 and 5.8 GHz are swept at the same time rather than in turn, so a full pass takes four to eight seconds. A drone that comes up on any of the three is heard on the same cycle.

0404 / 06

An alert you can check

Most detectors leave you with a tone and a guess. When the signal carries, MIMIR puts the feed on the screen — so the operator confirms the contact instead of trusting it.

0505 / 06

One hand, no specialists

Detection has meant a vehicle, a mast and a trained RF operator. This is a device that comes out of a pouch, is scanning within seconds of power-on, and is read by whoever is holding it.

0606 / 06

Built for the whole shift

Six to eight hours on two swappable cells, charging over the same USB-C cable as everything else, in an IP54 housing at 650 grams. Kit that is heavy or flat gets left behind.

How it works
N.01

How it finds a drone

An FPV drone cannot be flown blind. The pilot needs the picture, so the aircraft transmits video continuously from the moment it powers up — and that transmission carries much further than the aircraft can be seen or heard. It is the loudest thing about a drone, and it starts before the drone is a problem.

MIMIR sweeps the three bands that traffic sits in. It does not take them in turn; it takes them in parallel, so a full pass across roughly two and a half gigahertz of spectrum completes in four to eight seconds. When energy appears that has the structure of a video carrier, the unit sounds and lights immediately, and shows which band and channel it landed on.

If the signal is strong enough to lock, the decoder runs and the feed appears on the 3.5-inch screen. That step is what separates a detection from an assumption. Interference, a badly sited access point and a hostile aircraft all produce an alert on a cheap detector; only one of them produces a picture.

N.02

Passive, and why that decides things

MIMIR has no transmitter. It receives, and that is the entire architecture. The practical consequence is that operating it is undetectable: there is no emission for anyone to direction-find, so using it does not trade your position for their position.

That is the opposite of a jammer. A jammer transmits deliberately, at power, and announces both that it exists and roughly where it is. It also disrupts whatever else is using that spectrum — including, frequently, your own radios. In most jurisdictions it is tightly restricted or outright unlawful for anyone outside a narrow set of authorised users.

A receive-only device sits in a different category. It creates no interference because it creates no signal. Rules on receiving equipment vary by country and by what you do with what you receive, so treat this as the engineering fact it is rather than as legal advice — but the distinction between listening and transmitting is the one that regulators draw, and MIMIR is firmly on the listening side of it.

N.03

What a detection actually gets you

Time, first. Video reaches MIMIR well before the aircraft is overhead, and the gap between the alert and the arrival is the whole point — it is the interval in which a vehicle moves, a group disperses, or a weapon is readied.

Then discrimination. The feed tells you what kind of aircraft you are dealing with and what it is doing. A drone orbiting a road junction is a different problem from one running a straight line overhead on its way somewhere else, and the picture makes that obvious in seconds.

And finally a hand-off. The band, the channel and the bearing are the inputs an effector needs. MIMIR carries no weapon and does not pretend to: it finds the aircraft and gives the track to whoever is going to do something about it.

Received spectrum
PARALLEL SWEEP · FULL RANGE IN 4—8 S1.3 GHz900—1680 MHz3.3 GHz3060—3700 MHz5.8 GHz4990—6000 MHz1 GHz2 GHz3 GHz4 GHz5 GHz6 GHzDRAWN TO SCALE · LINEAR
BAND 11.3 GHz900—1680 MHz

Long-range and penetrating. Favoured where the aircraft has to see through structure or trees.

BAND 23.3 GHz3060—3700 MHz

The band operators move to when 5.8 is congested or being watched. Often missed by two-band sets.

BAND 35.8 GHz4990—6000 MHz

The common case. Most consumer and improvised FPV airframes transmit here by default.

Employment

Where it is used

  • 01Vehicle movement and convoy overwatch
  • 02Fixed sites, depots and critical infrastructure
  • 03Forward positions and observation posts
  • 04Border and perimeter patrols
  • 05Airfield and approach monitoring
  • 06Public events and temporary security cordons

What it will not do

Every sensing method has a blind spot. These are MIMIR’s, stated plainly — a capability you find out about in the field is worse than one you were told about here.

A silent drone is a silent drone

MIMIR finds aircraft by their transmissions. An airframe flying a pre-loaded route with its video off, or one on a fibre-optic tether, emits nothing to hear. Those need radar, optical or acoustic detection — and anyone who tells you their RF set catches them is selling you something.

Range is a conversation, not a number

Up to four kilometres is what the hardware supports with a strong transmitter, clear line of sight and a quiet spectrum. Terrain, structures, weather, the drone's own output and the local RF background all move that figure, sometimes by a lot. Treat the ceiling as a ceiling.

Bearing, not a grid reference

The unit gives you direction to the emitter and the strength of what it hears. It is not a positioning system: it will not hand you coordinates for the aircraft or for the operator flying it.

It detects; it does not defeat

There is no effector here and no jamming function. MIMIR is the sensor at the front of a counter-drone chain — cue HEIMDAL, cue a gun team, cue a decision. On its own it buys awareness and time, which is usually the scarce thing.

Specification
UNIT
Form factorHandheld, one-person operation
Dimensions95 × 158 × 47 mm, less antennas
Mass650 g
HousingImpact-resistant PETG
Ingress protectionIP54 — dust, splashing water
Primary display3.5 in — decoded video
Status displayChannels, histogram, cell voltage
Storage temperatureTo +60 °C
RECEPTION
ArchitecturePassive receiver — no emission
Coverage900–1680 / 3060–3700 / 4990–6000 MHz
SweepFull range in 4–8 s, bands in parallel
Detection rangeTo 4 km, conditions permitting
Band selectionAny band enabled or disabled
SensitivityManual or automatic, per band
False alarmsNon-video interference filtered; channel blacklist
Scrambled videoInverted-video descrambler
Antennas3 × SMA female — accepts higher-gain sets
TuningAutoscan, or manual channel selection
POWER
Cells2 × 21700 Li-ion, 2S, 4500 mAh, 33.3 Wh
Cell accessSwappable in the field, no tools
Runtime6–8 h continuous
ChargingUSB-C, quick-charge source required
Charge time4 h to full, while still scanning
Voltage readoutActual cell voltage, not an estimate
Low batteryWarning at 7.0 V, shutdown at 6.4 V
EMPLOYMENT
RoleEarly warning and situational awareness
SignatureNone — receiving is not emitting
AlertingAudible and visual on acquisition
CueingHands a bearing to other C-UAS systems
TrainingNo RF background required
AuthorityInformation only — no effector
Time to first sweepSeconds from cold — pre-calibrated
Questions

Asked and answered

What buyers ask about passive detection, answered without the hedging. Anything not covered here, put to us directly.

Ask us something else
Q.01What is the difference between a detector and a jammer?

A passive detector listens for the signals a drone already transmits and tells you what it heard. A jammer transmits its own signal to break the link between aircraft and operator. The detector is invisible in use and interferes with nothing; the jammer is loud, locatable, disruptive to your own radios, and in most places heavily restricted.

Q.02Which frequencies does MIMIR cover?

Three bands: 900–1680 MHz, 3060–3700 MHz and 4990–6000 MHz — the 1.3, 3.3 and 5.8 GHz FPV video bands. All three are swept in parallel, and any of them can be switched off if a band is unusable in your environment.

Q.03Does it work on drones that do not broadcast Remote ID?

Yes. Remote ID is a cooperative broadcast that anyone building an aircraft to cause trouble simply omits. MIMIR ignores it and listens for the video downlink instead, which is not optional if the aircraft is being flown by a human who needs to see.

Q.04Will it detect a fully autonomous drone?

No — and neither will any other RF receiver. An aircraft flying a pre-programmed route with no video transmission has nothing to detect. That is a genuine limitation of the method, and it is why RF detection sits alongside radar and optical sensing rather than replacing them.

Q.05How far away can it hear something?

Up to about four kilometres in good conditions. That figure assumes a strong transmitter, line of sight and a quiet spectrum; terrain, buildings, weather and local RF traffic all reduce it. Anyone quoting a single guaranteed range for RF detection is quoting a laboratory.

Q.06Can the drone operator tell they are being monitored?

No. MIMIR contains no transmitter, so there is nothing to detect and nothing to direction-find. This is the main reason to reach for a passive receiver before anything else in the chain.

Q.07What does an operator need to know to use it?

How to switch it on and how to read a screen. The unit ships pre-calibrated and is sweeping within seconds of power-on; there are no frequencies to program and no baseline to establish. Sensitivity can be tuned per band if the environment demands it, but the defaults are the working configuration.

Q.08How is this different from a phone app?

Detection apps read Remote ID broadcasts or public flight data — cooperative sources that a hostile aircraft will not be using. MIMIR is a receiver with real antennas and real front ends, working on the signal itself.

Q.09Does it record what it receives?

— (indicative TBC)

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