Intruder detection · Southwest Microwave
A puddle can put out a microwave field.
Southwest Microwave makes microwave barriers and fence and buried sensors. Microwave goes through the fog that blinds anything optical, and in exchange it is the most ground-sensitive thing there is. What they detect, where they fail and what civil works they need.
What it is, and where it turns up.
An American manufacturer specialising in perimeter detection. Its best-known family is the bistatic microwave barrier —transmitter one side, receiver the other— and it also makes fence sensor cable and buried cable, which is the combination usually needed in practice.
It turns up where the perimeter is demanding and the response costs: substations, fuel depots, chemical plants, data centres, ports, airports, military and prison sites. And in small places with a very specific problem: a gap with no fence, an open yard, the space between two industrial units.
It also turns up a lot as reinforcement for a fence that already has detection. A field inside the fencing turns the perimeter into two lines: one detects the fence being touched and the other that somebody has got through. Requiring both to see the same thing is the most effective way of bringing the false alarm down without losing detection.
What a microwave field really detects.
Between the transmitter and the receiver an invisible cigar-shaped volume forms, narrow at the ends and wide in the middle. The receiver listens to a steady signal and any body entering it alters that signal. That is the whole principle, and its virtues and its faults come out of it.
First, it does not care about light or heat, and it goes through rain and fog far better than anything optical: where an infrared beam gives alerts every winter morning, a microwave field keeps working. Second, it detects the slow — whoever crawls very slowly or rolls, which is exactly what somebody does when they know there is detection.
Third, it needs no fence and no trench: it covers a gap or an open yard with a pair of heads and no more civil works than the posts. And fourth, it is volumetric and not linear: it does not detect a line being crossed, it detects that somebody is inside a volume, so it is hard to go over or under a properly sized field.
Where it falls down. This is the bit to read.
Everything that follows really happens and almost none of it appears on a data sheet.
- Standing water. A puddle inside the field reflects it and distorts it, and the alerts start every time it rains. It is fixed with drainage and levelling, not with sensitivity. It is the number one cause, and the one most often attacked by fiddling with the equipment.
- Vegetation. Grass growing inside saturates it, and it grows by itself: a stretch that was clear in March has thirty centimetres of grass in May. The cleared corridor is a task with a name in the contract.
- Settled snow, which raises the ground level and narrows the volume from below. Adjusting in June and calling the stretch good is no use where there is a real winter.
- Undulating ground. The volume runs straight between the two heads; the ground does not. A dip or a ditch leaves a space underneath you can crawl through. Where it cannot be levelled, the stretch gets split in two.
- Metal that moves inside it: a loose fence, a gate, a sign, a tarpaulin, a van parked where there used to be nothing. All of that alters the signal with every gust, and it shows up after handover because nobody warns you they have left the lorry there.
- The dead zone next to the heads, where the volume has not formed yet. That is why two stretches are not put in line and end to end: they are offset sideways and overlapped.
- And interference between stretches. Two nearby pairs on the same frequency get in each other's way, and the symptom is a perimeter that raises alerts with nothing happening and with no pattern. It is solved by alternating frequencies in the project, or chased for months.
The installation is eighty per cent of the result.
With microwave it is literal: the same pair of heads can be flawless on one stretch and hell on the next.
The ground first: a corridor levelled, compacted, drained and cleared, and staying that way. That is civil works and it is part of the detection, even if on the quotation it looks like somebody else's item. A field over uneven ground with puddles is not fixed by configuring it.
Then the posts: rigid heads, anchored in concrete, with no vibration and no play. A tube driven into the ground or a head bolted to the fence is a guarantee of trouble, because the fence moves with the wind and the system detects its own movement.
The height and the adjustment of the volume decide what gets in: too low and it takes in rabbits, bags and leaves; too high and it leaves a gap underneath. And the adjustment is per stretch, because each stretch's ground is different. The overlap with a sideways offset is the rule most often broken and the one that creates the textbook hole. The final test is done crossing walking, running, crawling and rolling, and again after the first heavy rain — which is when the puddles nobody saw appear.
Verifying: what turns an alert into a decision.
When a stretch raises an alert, the only thing you know is that something has entered that volume: a person, a wild boar, a bag, yesterday's puddle. And the two options for whoever is on duty are both bad — send a patrol every time, which soon stops happening, or send nobody and hope.
With an image, the alert arrives with the seconds of video from the stretch that generated it. With microwave, verification also has a diagnostic use worth as much as the operational one: it is the only practical way of knowing why that stretch tripped and, with that, of fixing the ground problem behind it.
And here something has to be declared: in the same house there is IRIS Neural, the NVMS from Infinity Neural, the other company in this group. It is our own product, and we say so because recommending your own without warning wrecks everything else. It adds the image of what set the alarm off; it does not replace the sensor or the panel. With other video software it is done too. With nothing that lets you look, it is not.
There is no good technology. There is technology suited to that perimeter.
Microwave is the best answer for a stretch with no fence, for a gap, for an open yard and for a place with fog. And it is the worst for uneven ground that cannot be levelled, for a corridor that is not going to be kept clear and for a yard where people park wherever suits them.
That is why a real site is never one single technology: cable on the sound fence stretches, microwave in the gaps and as a second line inside the fencing, buried cable where nothing can be seen, beams in a narrow passage, contacts on the doors, and cameras over the top of all of it.
Two technologies that fail for different reasons do not fail at the same time, and holding each to account against the other is the real tool against the false alarm. The price is a little sensitivity, and it is a decision per stretch. We are not going to say this brand is better than the others: in microwave there is more than one house that does this well, and what decides is the geometry of the stretch, how it is powered and what support is behind it.
What we do with it.
- Walking the perimeter on foot, stretch by stretch: slope, undulations, where it floods, what grows, what gets parked and what metal moves. And after rain if possible — the puddles are half the diagnosis.
- The civil works item stated separately and without decoration: levelling, compaction, drainage and posts anchored in concrete. If the ground cannot be prepared, we say so and propose another technology for that stretch.
- The project with the stretches split according to the ground, the overlaps with a sideways offset drawn in, the dead zones marked and the frequencies shared out.
- The second line where it is needed, and which stretches require two technologies to agree. With the price alongside, so the client decides with the figure in front of them.
- The adjustment per stretch by walking it, not with a catalogue value. And with wind if you can wait for a windy day, which is the best test there is.
- The commissioning with a record sheet written beforehand —walking, running, crawling and rolling, at the ends, the middle and the joins— and a second pass after the first rain. Plus clearance and drainage inside the maintenance contract: if they are not written down, the stretch degrades on its own every spring.
The grade, the alarm receiving centre and what comes after.
A microwave barrier is a zone on a panel. The EN 50131 standards classify systems into security grades, and each grade demands specific things of the equipment, the cabling, the power supply and the tamper detection. Which grade each piece of equipment supports is read in its documentation; whether the installation meets that grade is another matter. We do not say here which one we hand over: it depends on the project, and it is stated in writing by whoever signs.
Connecting to an alarm receiving centre is a separate decision, with its own regulations and its own contract, and outdoors the protocol has to be written down stretch by stretch: what is done with each alert and what gets verified before moving anybody. Who provides that service is settled in a quotation, not on a website.
The day to day is the client's: arming by stretch, looking at the log, knowing which stretch is which number. What they do not touch is the sensitivity of a stretch or the aim of a head — turning it down so it stops being a nuisance is how a stretch stops detecting without anybody noticing, and with microwave it is especially silent because there is nothing to look at. And the isolation that got left in place is the way in: with an expiry date and with that date in the report.
The other eight in this group.
Four more perimeter houses and the four control panels all of this connects to. None is better than another: what changes is the ground they hold up on.
Get started
Does it flood? Then let's start there.
Tell us which stretch has to be covered, whether there is a fence or not, what the ground is like, whether it floods and what gets parked inside. We will tell you whether the stretch is one for microwave, what civil works it needs and what technology we would put alongside it.