Latest / Logosofia no Dia a Dia / Wi-Fi Through Concrete Bunkers
Transcript
- [Prompt] custom: We've talked about access points before, which for anyone getting into home networking I would alway | Hosts: corn, herman [Response] Corn: Daniel sent us this one — he's wrestling with something that basically every Israeli renter who cares about their network has banged their head against. You know the gold standard: wired-backhaul access points, unified gear, done. But when you're renting and can't drill holes through the walls, you're stuck with a single AP trying to punch through a maze of small rooms. And then there's the mamad — the protected room that's essentially a concrete-and-steel bunker with its own HVAC, often serving as a home office. The question is, can you configure a single access point, or choose a specific model, to actually make this work? And when Wi-Fi simply cannot penetrate, are there any non-destructive solutions that don't involve the disaster that is powerline Ethernet on gigabit fiber? Herman: This is the networking equivalent of "how do I cook a five-course meal in a hotel room with only a kettle." And it matters way beyond Israel now, because post-pandemic, people are working from reinforced concrete basements, converted bomb shelters, steel-framed loft apartments. The mamad is just the extreme end of a spectrum that a lot of people are suddenly living on. Corn: The universal advice is "run Ethernet, mount APs on the ceiling, stop overthinking it." But the universal advice assumes you own the walls. Daniel's situation strips away every assumption that networking guides are built on. Herman: What I love about this prompt is it forces us to get specific. Not "what's the best router," but "given this exact physical obstacle — twenty to thirty centimeters of reinforced concrete with steel rebar — what configuration knobs can you actually turn, and which ones actually matter? Corn: Where do we even start with this? Because I feel like there's a whole layer of bad advice out there. People hear "concrete walls" and immediately jump to "more power" or "mesh system. Herman: Both of which are traps in this context, and we should probably explain why before we get to what actually works. But let's start with the physics of the problem itself, because once you understand what these walls are doing to your signal, the solutions become a lot less counterintuitive. Herman: The attenuation numbers are genuinely staggering. A standard American drywall interior wall knocks your signal down by maybe three dBm. A European brick wall, maybe six to eight. An Israeli mamad wall — twenty to thirty centimeters of reinforced concrete with steel rebar — we're talking thirty to forty dBm of loss at two point four gigahertz. That's not a wall. That's a deliberate signal denial structure. Corn: It's a Faraday cage with a doorbell. Herman: It's not just the mamad. Israeli apartments are partitioned into many small rooms — bedrooms, salon, kitchen, bathroom, all separated by what are essentially cinderblock or reinforced gypsum partition walls. So even before you reach the bunker at the end of the hall, your signal's already been through four or five walls, each taking its own bite out of the link budget. Corn: Compared to the open-plan layouts that are standard in a lot of US apartments, where one AP in the living room covers the whole space because there's nothing between it and the bedroom but air and regret. Herman: And European apartments, even older ones with thick stone walls, tend to have fewer internal partitions. The Israeli floor plan is uniquely hostile to radio propagation — lots of small boxes, each wrapped in something dense. Then you add the mamad, which since the nineteen nineties has been legally mandated in every new residential building. It's a room designed to keep out chemical and biological agents, with an independent HVAC system and a steel door that weighs more than I do. Corn: The signal has to contend with what's essentially a bank vault that someone decided to put a desk in. Herman: That's the core tension Daniel's asking about. You can't drill. You've got one AP. It's sitting in a hallway or a corner of the salon because that's where the fiber comes into the apartment. And it's supposed to somehow serve a home office that's inside a concrete box with a steel door. The question isn't "how do I get perfect coverage." The question is "what's the best I can do with the knobs I'm actually allowed to turn. Herman: Let's talk about what you actually can control, because the physical constraints are fixed but the configuration levers are surprisingly powerful. The first and most underrated one is height. Mounting an access point high — on top of a bookshelf, a tall cabinet, or even using a tension rod to get it near the ceiling — can reduce floor-level attenuation by forty to fifty percent in concrete buildings. There's solid research backing this up. Corn: Because the signal isn't having to go through furniture and the lower, denser parts of walls? Herman: Partly that, but also because at ceiling height you're often shooting over the top of partition walls rather than through them. Interior walls in Israeli apartments don't always go all the way to the structural ceiling — there's frequently a gap, or at least thinner material at the top. So you're finding a path of least resistance that simply doesn't exist at desk level. Corn: The difference between "AP sitting on the TV stand" and "AP perched on top of the armoire" isn't marginal — it's potentially the difference between usable signal and a spinning wheel of despair in the back bedroom. Herman: There's a case study from a three-room Tel Aviv apartment that illustrates this perfectly. Central hallway layout, AP originally in the corner of the salon. Coverage in the far bedroom was abysmal. They moved the AP to the hallway ceiling junction — not even a different room, just higher and more central — and the signal in that bedroom improved by fifteen dBm. That's not a tweak, that's a transformation. Corn: You didn't drill a single hole. Command strips, a shelf, done. Herman: Now, placement gets you part of the way. The next lever is what the AP itself is doing with its antennas, and this is where beamforming comes in. Modern access points with MIMO — multiple input, multiple output — can actually steer the signal. Instead of broadcasting equally in all directions like a lightbulb, beamforming focuses energy toward the specific client device it's talking to. Corn: It's less "shout louder" and more "aim the megaphone. Herman: The effect is real, but there's a catch — both the AP and the client device need to support it. Most modern phones and laptops do, but if you've got an older smart TV or a cheap IoT gadget, it won't benefit. Still, for the devices you actually care about — your work laptop, your phone — beamforming can be the difference between a stable connection and constant drops through two concrete walls. Corn: Which APs actually deliver on this? Because "beamforming" is one of those spec-sheet words that every manufacturer slaps on the box. Herman: Right, implementation quality varies enormously. The Ubiquiti U6 Pro and the TP-Link EAP670 have both been tested to maintain signal through two concrete walls with less than twenty dBm loss. That's outperforming typical consumer mesh nodes by five to ten dBm in the same conditions. These are enterprise-leaning access points with properly tuned antenna arrays — they're not magic, but they're engineered for exactly this kind of hostile RF environment. Corn: Daniel's instinct to go with a single, high-quality AP rather than a mesh system is actually the right call in this context. Which feels counterintuitive to anyone who's watched a mesh system commercial. Herman: It's one of the biggest misconceptions out there. Mesh systems rely on nodes talking to each other wirelessly. In a concrete-heavy apartment, those nodes often can't hear each other through the walls any better than your phone can. So you've spent extra money on additional hardware that's all suffering from the same inter-node deafness. A single well-placed AP avoids that problem entirely — there's no backhaul to fail because there's no mesh. Corn: It's like hiring three translators who all speak different languages and hoping they'll figure it out. Herman: Then there's the channel selection issue, which is especially relevant in dense urban Israeli neighborhoods. You've got forty apartments within range, all blasting Wi-Fi on whatever channel their ISP's router auto-selected. Two point four gigahertz penetrates concrete better — that's just physics, longer wavelengths bend around obstacles more effectively — but the band is absolutely congested. Corn: Five gigahertz is a ghost town by comparison, but it dies at the first piece of rebar. Herman: The practical rule is: use two point four for the mamad and other far rooms where penetration matters more than speed, and five gigahertz for open-plan areas where you're in the same room as the AP. Most modern APs let you run both bands simultaneously with the same SSID, and the client device will pick — but you can nudge this by adjusting the minimum RSSI thresholds if your AP supports it. Corn: The channel itself — you said auto-selection is part of the problem. Herman: Auto channel selection on consumer gear is often terrible. It'll pick channel four because it looks momentarily quiet, not realizing it's overlapping with both channel one and channel six and creating interference for everyone. You want to manually set your two point four gigahertz radio to channel one, six, or eleven — whichever is least congested — using a Wi-Fi analyzer app on your phone to survey what your neighbors are actually using. Corn: That's a free tweak that takes five minutes and requires zero hardware. Herman: While you're in the settings, there's one more counterintuitive move: reduce your transmit power. Everyone's instinct is to crank it to maximum, but in a small Israeli apartment with lots of reflective surfaces, high power causes self-interference. The signal bounces off those concrete walls, creates multipath distortion, and your devices can't decode what they're receiving. Plus, if the AP is shouting at full volume but your phone can only whisper back, you get client starvation — the AP can reach the phone, but the phone can't complete the handshake. Corn: "more power" is the networking equivalent of turning your car stereo up to eleven and wondering why the bass is distorted. Herman: Drop it to medium or even low, especially on the five gigahertz radio. You'll often get more stable throughput because you're reducing the noise floor and letting the AP and client operate at power levels that actually match. It's one of those things that sounds wrong until you see the speed test results, and then you never go back. Corn: We've squeezed everything we can out of the single AP. It's high, it's central, channels are locked, power's dialed back. And yet — the mamad still sits there like a concrete middle finger to everything we've just discussed. Herman: The mamad is a different class of problem entirely. We're not talking about attenuation anymore — we're talking about near-total signal extinction. Steel door, steel rebar grid, thirty centimeters of reinforced concrete, independent HVAC with its own metal ducting. Even with the door slightly ajar, the steel frame creates what's called a waveguide null — essentially a dead zone where the geometry of the metal actually cancels out certain frequencies rather than just blocking them. Corn: The door being open a crack isn't the partial victory you think it is. You're still trying to shout through a keyhole made of signal-canceling geometry. Herman: And this is where Daniel's instinct about powerline is dead on. He called it a disastrous idea for gigabit fiber, and the research backs that up completely. In Israeli apartments, powerline adapters typically deliver a hundred to two hundred megabits per second in the real world — not the twelve hundred printed on the box. Corn: That's a ninety percent haircut. Herman: It's not just throughput. The latency is wildly inconsistent because of phase noise from appliances — your fridge compressor kicks on, your connection stutters. Israeli apartments often have three-phase power with shared neutral wiring between units, which means your neighbor's air conditioner is introducing noise on your powerline network. It's a last resort, and I mean absolute last resort. Corn: Powerline is the networking equivalent of "we have Ethernet at home." What's the alternative that actually works? Herman: This is where MoCA becomes the unsung hero of Israeli apartment networking. MoCA — Multimedia over Coax Alliance — runs Ethernet over coaxial cable. And here's the thing most people don't realize: a huge number of Israeli apartments have legacy TV coax runs already built into the walls, including into the mamad. It was standard for years to wire every room for cable TV. Corn: There's a data highway already sitting in the wall, and nobody's using it because everyone streams now. Herman: MoCA two point five adapters — specific models like the goCoax MoCA two point five or the ScreenBeam ECB seven two five zero — can push up to two point five gigabits per second full-duplex over that existing coax. Real-world latency is three to five milliseconds. That's functionally indistinguishable from Ethernet for anything short of competitive esports. Corn: You don't need to drill anything. You screw the adapter onto the existing coax port, plug in Ethernet on both ends, done. Herman: A pair of MoCA adapters costs about a hundred and twenty dollars. That's cheaper than most mesh systems, and it gives you wired backhaul into the room that Wi-Fi literally cannot penetrate. If you've got coax in the mamad, this is the answer. Stop reading, go buy the adapters. Corn: What if there's no coax? Daniel's apartment might not have it, or the previous owner might have ripped it out during a renovation. Herman: Then you go point-to-point wireless bridge. Something like the Ubiquiti NanoStation five AC — it's designed for exactly this kind of scenario. You mount one unit outside the mamad, one inside, using adhesive mounts or command strips on the wall. These things have a link budget north of sixty dBm. They're built to punch through obstacles that would make a normal access point weep. Corn: It's a dedicated wireless tunnel through one specific wall, rather than trying to cover the whole apartment from one point. Herman: Because it's a focused beam rather than omnidirectional broadcast, it's far more efficient at penetrating dense materials. You're not trying to light up the whole room — you're just establishing a single high-bandwidth link. Put a small switch on the inside, connect your office gear, and you've got wired speeds in a room that Wi-Fi can't touch. Corn: What about the mounting itself? We keep saying "adhesive mounts," but some of these APs and bridges aren't exactly lightweight. Herman: For lightweight access points, the heavy-duty Command strips rated for five kilos work fine — I've seen installations that have held for years. For ceiling placement, tension rods between walls with a small shelf attached are brilliant — completely non-destructive, removable in thirty seconds. And for cable management, adhesive raceways along baseboards hide everything without a single hole. The rental-friendly networking toolkit exists, it's just not what Best Buy is going to sell you. Corn: Alright, let's boil all of this down into a concrete plan you can execute this weekend. Step one: get the AP high and central. Bookshelf, tension rod, top of a cabinet — whatever gets it near the ceiling and as close to the middle of the apartment as that fiber entry point allows. This alone can buy you forty to fifty percent better coverage. Herman: Step two: pull out a Wi-Fi analyzer app, find the least congested channel among one, six, and eleven on the two point four gigahertz band, and manually lock it in. While you're in there, dial the transmit power down to medium. Both of these are free and take five minutes. Corn: Step three: check every room, including the mamad, for a coaxial port. If you find one, stop researching. Buy a MoCA two point five adapter kit — goCoax or ScreenBeam, about a hundred and twenty dollars for a pair — and you've just given yourself wired Ethernet into the bunker without drilling a single hole. Herman: Step four: if there's no coax, grab a point-to-point wireless bridge like the NanoStation, mount it with adhesive strips on either side of the mamad wall, and put a small switch inside. That's your dedicated data tunnel through the concrete. Corn: The MoCA adapter kit is really the one purchase that changes everything here. It's cheaper than a mesh system, it delivers wired reliability, and it solves the problem that Wi-Fi physics literally cannot solve. If you've got coax in the walls, this is the closest thing to a cheat code. Herman: Then there's the moment where you have to be honest about the constraints. If the mamad door is closed for actual security reasons — fully sealed — no wireless solution works. You're inside a Faraday cage. The fallback is a flat Ethernet cable slipped under the door as a temporary run. It's not elegant, but it's a gigabit connection, and you coil it up when you're done. Corn: The best network is the one that works within your constraints. Don't let perfect be the enemy of good — and don't let the fact that you can't drill holes convince you that you can't have a solid connection in that home office. Herman: Which does make me wonder — are we going to see building codes catch up to the reality that the mamad is now a home office? Right now the code mandates reinforced concrete, steel door, independent HVAC. Nothing about data. But you've got thousands of people working full-time inside what's essentially a Faraday cage, and the official solution is "run a flat cable under the door when you need internet. Corn: It's a fascinating gap. The mamad was designed for a world where the threat was rockets and the use case was "survive for a few hours." Now it's "spend eight hours a day on Zoom calls." The design requirements haven't changed, but the functional requirements have completely transformed. Herman: I could see two paths. Either future building codes mandate at least one coax or Ethernet drop into the mamad — which would be trivial to add during construction and cost almost nothing — or we'll see mesh nodes with dedicated wireless backhaul radios that operate on frequencies better suited to concrete penetration. There's already research into using sub-gigahertz bands for backhaul in dense building materials. Corn: A conduit requirement during construction would future-proof the room for whatever cabling standard comes next, and it adds maybe fifty shekels to the build cost. Herman: Until that happens, the takeaway from everything we've laid out is refreshingly simple. You don't need to drill. You don't need to beg your landlord. You need to place your AP smartly, configure it properly, and if there's coax in the wall, buy a MoCA kit. If there isn't, a wireless bridge gets you there. The tools exist — they're just not the ones the marketing departments are pushing. Corn: That's really the final thought here. The best network is the one that works within your constraints. Don't let the fact that you can't do it the "right" way convince you that you can't do it at all. Herman: Thanks as always to our producer Hilbert Flumingtop for keeping us on the rails. This has been My Weird Prompts — if you found this useful, leave us a review wherever you listen, it helps other people find the show. Corn: We'll be back next time with whatever Daniel throws at us. And now: Hilbert's daily fun fact. Hilbert: Slovene is one of the only modern Indo-European languages to preserve the dual grammatical number — meaning it has separate verb forms and noun declensions for exactly two of something, a feature that was already vanishing from most related languages by the early Renaissance. Corn:...right.