Alright, today’s prompt from Daniel is a bit of a high-stakes engineering puzzle. He’s asking about building an impromptu mesh network using spare Android devices to get a signal several stories underground. Imagine you’re hunkered down, maybe three or four levels below the surface, and the traditional radio or cellular network just isn’t reaching you. You’ve got a drawer full of old Pixel phones and Samsungs. Can you actually string them together to create a digital lifeline?
Herman Poppleberry here, and I love this because it’s the ultimate "MacGyver" networking scenario. We’re moving away from the ideal world of shielded Cat 6 cabling and dedicated hardware into the messy reality of consumer electronics and software workarounds. By the way, today’s episode is powered by Google Gemini 1.5 Flash, which is fitting since we’re talking about the Android ecosystem.
It’s a fascinating challenge because underground environments are basically the natural enemy of high-frequency radiation. You’ve got rebar-reinforced concrete, lead pipes, and thick earth. It’s a Faraday cage designed by architects. Daniel wants to know if we can use these phones as ingress points, repeaters, and ultimately an access point. But before we get into the "how," Herman, we have to talk about the "if." Is a chain of old phones actually a viable network, or is it just a recipe for high latency and a dead battery?
It’s viable, but with massive caveats. Normally, when we talk about mesh, we think of something like Eero or Google Nest Wi-Fi, where the hardware is designed from the ground up to talk to other nodes on dedicated backhaul channels. Android phones aren’t built for that. They’re built to be endpoints. So, to make this work, you have to force them into roles they weren't exactly intended for. You’re essentially tricking the Wi-Fi radio into being a simultaneous client and an access point.
Right, and that’s where the software comes in. You can’t just go into the standard Android settings and hit a "Daisy Chain" button. It doesn't exist. Most stock Android builds are strictly "either/or"—you're either on Wi-Fi or you're a Hotspot using cellular data. So, what are we looking at? I know there are a few heavy hitters in this space. Meshrabiya is one that pops up in the open-source world.
Meshrabiya is brilliant because it’s specifically designed for this multi-hop scenario. It uses Wi-Fi Direct and local hotspots to route data across multiple devices. The goal is to make the entire chain look like a single network to the user at the bottom of the hole. But if you’re looking for something a bit more plug-and-play, you’re looking at apps like NetShare or PdaNet+. These are the go-to "no-root" tethering apps. They allow an Android phone to connect to a Wi-Fi source and rebroadcast that signal as a new hotspot at the same time.
I’ve used NetShare before to get around hotel Wi-Fi limits, but using it for a three-story vertical drop is a different beast. If I’m the "ingress" phone at the top of the stairs, I’m grabbing the outside signal. Then I’m broadcasting to the next phone. That phone connects to me and broadcasts to the third. It sounds simple, but I’m assuming the physics of that "rebroadcast" is where things start to fall apart. Does the hardware even support that kind of dual-radio operation natively?
Most modern chips from the last five or six years—think Snapdragon 845 and up—actually have the hardware capability called "Wi-Fi Station + AP" concurrency. It’s just that the Android UI usually hides it. NetShare essentially bypasses the system lock to engage both modes. But here's the catch: In networking, we call this the "Half-Bandwidth Rule." Most consumer Wi-Fi radios are half-duplex. They can’t send and receive at the same time on the same frequency. So, if your repeater phone is receiving data from the node above it and then passing it to the node below it using that same radio, it has to take turns. It spends half its time listening and half its time talking.
So, right out of the gate, you lose fifty percent of your potential throughput with every single hop. If I start with a hundred megabits at the surface, I’m down to fifty at the first repeater, twenty-five at the second, and twelve-point-five by the time it reaches me in the bunker. That's assuming perfect conditions, which we know underground bunkers definitely aren't.
And that’s the optimistic version. That doesn't even account for overhead, interference, or signal degradation through the air. In practice, by the third hop, you’re looking at low-bandwidth territory. A 2024 study on Wi-Fi Direct mesh networks showed that latency starts to skyrocket once you hit that fifth or sixth hop. We’re talking over a hundred milliseconds of ping. For a text message or a basic webpage, that’s fine. For a Zoom call or real-time coordination? It’s going to be a stuttering mess.
I love the idea of "jitter" being the silent killer here. It’s not just that the data is slow; it’s that it’s arriving in unpredictable clumps because each phone in the chain is struggling to manage those "turns" it has to take. You mentioned a case study in Tel Aviv from 2023 involving a multi-story parking garage. How did they handle that?
That was a fascinating test of Serval Mesh. They were trying to see if they could maintain a VoIP call through several layers of subterranean concrete. Serval is open-source and doesn't even need the internet; it creates its own cellular-like network over Wi-Fi. What they found was that "line of sight" was everything. If they put the phones inside the cars or behind pillars, the network collapsed instantly. They had to place the devices specifically in the stairwell landings to allow the signal to "pour" down the open vertical space.
It’s like a digital bucket brigade. If you spill too much water at each transfer, the person at the end of the line gets a dry bucket. So, if Daniel is setting this up, he’s got his ingress phone at the top. Where does he put the next one? If he puts it too far down, the connection is weak. If he puts it too close, he’s wasting phones. What’s the "Goldilocks" zone for placement?
The rule of thumb in these constrained environments is the "Fifty-Fifty" placement. You don't want to place your repeater where the signal is already dying. If your phone shows "one bar," it’s too late. The data rate has already dropped to its lowest modulation to survive the noise. You want to place the repeater where it still has a rock-solid connection—usually around negative sixty-five to negative seventy decibels milliwatt. If you have two bars of solid signal, that’s your spot.
And in a stairwell, that’s probably only what, ten or fifteen meters? Concrete is a brutal attenuator. I’ve seen 5G signals die just from a double-paned window, so four inches of reinforced concrete might as well be a lead wall. How much of the signal is actually penetrating the floor versus just bouncing off the walls of the stairwell?
In a bunker, almost zero percent is going through the floor. You're dealing with "Multi-path interference." The Wi-Fi signal hits the concrete, some of it is absorbed by the water molecules in the cement, and the rest bounces. If you have a metal fire door in that stairwell, it acts like a mirror. If that door is closed, you might lose the link entirely. That's why you have to treat the Wi-Fi signal like a physical liquid. You want to place the phones so they can "see" each other around the corners of the stairs.
Concrete with rebar is basically a grid that scatters the signal. That’s why the "staggered stairwell" approach is the only way to go. You place a device on the landing of each floor. You’re essentially using the stairwell as a waveguide. The signal bounces off the walls and travels down the empty air of the shaft. If you try to go straight through the floors, you’ll be lucky to get through one level.
Let’s talk about the hardware for a second. We’re talking about "spare" devices. Does it matter if it’s an old Galaxy S8 versus a newer mid-range phone? Because I’m thinking about heat. If these things are running high-speed Wi-Fi radios at a hundred percent duty cycle, they’re going to get hot.
They will get incredibly hot. Older phones, especially those with Snapdragon 810 or 820 chips, were notorious for thermal throttling. If the phone gets too hot, the internal governor will downclock the processor and the radio to save the silicon. Suddenly, your "repeater" is crawling not because of the network, but because it’s literally melting. You want devices that are relatively efficient, and you absolutely must have them plugged into power.
That’s a huge point. If you’re in an emergency situation and you think your old Android phone is going to act as a mesh node for twelve hours on its original, degraded battery... you’re in for a rude awakening. Acting as a hotspot is one of the most power-intensive things a phone can do. We’re talking three to five hours max before it goes dark. And that's with a healthy battery! An old Pixel 2 with a bloated lithium-ion cell might last forty-five minutes under that kind of load.
And then your whole chain breaks. If node number two dies, nodes three, four, and five are now just expensive paperweights. This is why the "modem tethered to a router" idea Daniel mentioned is actually the smartest part of the plan. If you can get that final hop to terminate into a real travel router at the bottom, the router can handle the local distribution to your actual devices, like your laptop or primary phone. It takes the load off the last Android device in the chain.
I’m curious about the "IP conflict" issue. If I’m using something like NetShare across four devices, isn't each one trying to act as a DHCP server? You end up with "NAT behind NAT behind NAT." It’s like a Russian nesting doll of networking errors. Doesn't that break things like SSL certificates or secure banking apps?
It’s a nightmare for certain protocols. Every time you go through a NAT layer—Network Address Translation—the packet headers get modified. Basic web browsing usually survives it because HTTP is resilient, but if you’re trying to use a VPN or an encrypted messaging app like Signal that’s sensitive to packet alteration or timing, it might just refuse to connect. The triple-NAT scenario can also cause "MTU discovery" issues, where the packets are too big for the tunnel and just get dropped without warning. This is why specialized apps like Meshrabiya or Briar are better for this than just daisy-chaining hotspots. They handle the routing at a different layer to avoid that nesting doll effect.
You mentioned Briar. That’s an interesting one because it’s not trying to give you the "whole internet," right? It’s more about resilient messaging.
Briar is the gold standard for "the world is ending and I need to talk to my neighbor." It uses Bluetooth, Wi-Fi, and even Tor if the internet is available. In a bunker scenario, you could have a chain of phones running Briar, and even without any internet ingress at the top, they would create a local mesh. You could send a message from the bottom floor, and it would hop from phone to phone until it reached someone at the top. It’s slow—Bluetooth mesh is "kilobits per second" slow—but it’s incredibly reliable because it doesn't have the same overhead as a full Wi-Fi hotspot.
It’s the difference between trying to run a fire hose down the stairs versus just passing notes. If Daniel just needs to stay in touch with the surface, a Bluetooth mesh like Briar or Bridgefy might actually be more stable than trying to force a high-speed Wi-Fi chain through concrete. Bridgefy was famous during the Hong Kong protests in 2014 for exactly this. Thousands of people using their phones to hop messages across city blocks when the towers were jammed. But back to Daniel's specific setup: if he wants actual internet access, he's stuck with the Wi-Fi chain.
The tradeoff is always speed versus range. Bluetooth has better "penetration" in a sense because it’s a lower-power, simpler signal, but you aren't going to be watching YouTube on it. If Daniel’s goal is "radio connectivity," as in, he wants to use an app like Zello or a digital radio interface, he needs that Wi-Fi throughput. Zello, for instance, requires a relatively stable stream to handle the voice compression. If the jitter gets too high, the audio will just sound like robotic chirping.
Let’s look at the "hop limit" again. You mentioned five to seven hops as the functional ceiling. If each floor is roughly three to four meters, and we’re doing one hop per floor to keep that "two-bar" signal strength... that means you could theoretically get down twenty meters underground. That’s a deep hole. That’s a serious facility. But wouldn't the interference from all those overlapping 2.4GHz signals eventually just choke the whole thing out?
It is a major risk. You have to consider the "re-entry" problem. Every time the signal hits a new device, there’s a processing delay. The Android OS has to receive the packet, look at the routing table, and send it back out. In a dedicated router, this happens in microseconds. On an old Android phone running a background app? It might take five or ten milliseconds. You add that up over seven hops, and your round-trip time is already suffering before the packet even leaves the building.
I can see the "cheeky" side of this, though. You could technically set this up as a permanent backup. If you have power outlets in your stairwell, you just velcro these old phones to the wall, keep them plugged in, and leave the app running. It’s a "break glass in case of emergency" network. But Herman, what happens if the ingress phone loses the primary signal? Does the whole mesh just sit there spinning its wheels?
Most of these apps aren't smart enough to self-heal. If the top node loses the internet, the bottom nodes will still show a "strong Wi-Fi signal" because they’re still connected to each other, but they’ll have that annoying little "No Internet" exclamation point. This is why I actually prefer the LoRa approach if the situation is truly dire. Have you looked at Meshtastic?
I have! That’s the one where you buy those little thirty-dollar radio boards and pair them to your phone via Bluetooth. It’s not "Android-only" because it requires extra hardware, but it turns the phone into a terminal for a much more powerful radio network. I've seen people get miles of range out of those with a clear line of sight.
LoRa—Long Range radio—operates at much lower frequencies, like nine-hundred megahertz. Those waves are much better at wrapping around obstacles and penetrating materials than two-point-four gigahertz Wi-Fi. You could probably skip two floors per hop with LoRa. But, again, we’re talking about text-only data. Daniel’s prompt specifically mentions "ingress to pick up the network," which implies he wants the data from the surface to flow down.
So if we’re sticking to the "Android-only" hardware constraint, we’re effectively building a high-latency, fragile, but functional relay. I’m thinking about the practical setup for Daniel. He’s in a bunker, he’s got his phones. Step one: install something like NetShare on all of them. Step two: get to the top of the stairs. What's the best way to secure these things? You can't just leave them on the floor where someone might step on them.
And step three is the "testing phase." This is what most people skip. You can’t just set it and walk away. You need to run a persistent ping from the bottom phone to the top phone. If you see the latency jumping from twenty milliseconds to five hundred, you know one of your "links" is too far apart. You have to physically move the phones until that ping stabilizes. It’s a game of inches. I'd recommend using Command strips or even heavy-duty magnets if the stairwell has steel beams.
It’s almost like tuning an instrument. You’re looking for that resonance where the radios aren't fighting each other. What about interference? If you have multiple phones all broadcasting hotspots in a narrow stairwell, aren't they going to drown each other out? Especially in the 2.4GHz band which only has three non-overlapping channels.
They absolutely will if they’re all on the same channel. Most of these "no-root" apps don't let you manually pick the Wi-Fi channel. They just grab whatever is open. If node A is on channel six and node B is also on channel six, they’re going to be screaming over each other. This is the "hidden node problem" in networking. The phones can hear their neighbors, but they can’t hear the neighbors' neighbors, so they both try to talk at the same time and the packets collide. It’s like two people trying to have a conversation while someone else is shouting the same words right next to them.
So the "mesh" actually becomes a "mess." If you’re doing this, you ideally want to stagger the channels. Node one on channel one, node two on channel six, node three on channel eleven. That way each link in the chain has its own clear lane. But again, you need an app that gives you that level of control. Most of the simple "hotspot" apps are too basic for that. Are there any "Pro" apps that allow channel locking?
If you root the phones, you have total control. You can use a terminal emulator to force the Wi-Fi chip onto a specific frequency. But for the average user, you’re at the mercy of the app’s auto-channel selection. This is why the technical literacy Daniel has is so important here. You can’t just hand this to a layman. You need someone who can go into the developer settings, maybe even use ADB—the Android Debug Bridge—to tweak the Wi-Fi scan intervals. If the phone is constantly "searching" for a better signal while it’s trying to repeat one, it’s going to drop packets every time it performs a scan.
I’m envisioning a scenario where you have these phones taped to the walls of a bunker, and a missile alert goes off. You’re sitting there, hoping your "Pixel 3 relay" holds up so you can check the news. It’s a strange world we live in where our "survival gear" is basically a collection of 2018 flagship phones and some USB-C cables. It's the ultimate digital scrounging.
It’s the ubiquity of it that makes it brilliant. We have billions of these devices sitting in drawers. Each one has a sophisticated radio, a powerful processor, and a decent amount of RAM. Using them as a mesh network is just reclaiming that "e-waste" for something life-saving. Even if it’s only twelve megabits per second, that’s enough to get an emergency broadcast, a weather map, or a message to your family. Think about the humanitarian applications—setting up a quick network in a collapsed building or a flooded area where the cell towers are down.
Let’s talk about the "modem tethered to a router" part of Daniel's prompt. He says the final phone could be tethered into a router. That’s actually a great way to handle the "last mile" inside the bunker. You take the USB-C out of the phone, plug it into the WAN port of a travel router that supports USB tethering—like those GL-iNet ones we always talk about—and then the router handles the Wi-Fi for everyone in the room. This also means the phone isn't doing double-duty as an AP for the end users.
That’s the pro move. It solves the "Half-Bandwidth" issue for the final hop. Since the phone is handing the data to the router via a wire, its Wi-Fi radio is only doing one thing: listening to the node above it. It doesn't have to rebroadcast. That saves twenty-five to fifty percent of your bandwidth right there at the most critical point. Plus, the router has much better antennas for covering the inside of the bunker. You can actually use a high-gain antenna on that router to push the signal through the bunker's interior walls.
So the "ideal" chain is: Surface Wi-Fi to Phone A, Phone A to Phone B via Wi-Fi Direct, Phone B to Phone C via Wi-Fi Direct, and Phone C to Router via USB cable. That gives you three floors of depth with only two "wireless" jumps. That’s actually a very solid setup. You’d probably keep seventy percent of your original speed if the signal strength is good. And since Phone C is tethered, it's also being charged by the router's USB port, which solves one of the power problems.
And you avoid the NAT issues because the router can be configured to handle the IP assignments for the local clients. It’s a hybrid approach—part ad-hoc mesh, part traditional infrastructure. It’s much more stable than trying to let five different Android phones all try to manage their own DHCP pools.
I’m still stuck on the "ingress" point. If the surface is dangerous or exposed, you can’t just leave a phone sitting on the sidewalk. You have to hide it. But if you hide it in a metal box or under a heavy lid, you lose the signal. It’s a physical security problem as much as a networking one. How do you camouflage a node while maintaining RF transparency?
You’d probably want to put it in a plastic, weather-proof container near a window or a vent. Something that’s RF-transparent like a Tupperware bin or a PVC pipe. But Daniel’s context is usually more about "safe rooms" or "shelters" within a building. In that case, the "ingress" phone is just sitting in the hallway upstairs where the main router is. It’s less about "clandestine" and more about "extension." You're basically building a bridge from the world of light and signal down into the dark.
Right, extending the "digital reach" where the architecture is trying to kill it. I’ve noticed that in a lot of modern buildings, even without being "underground," the Wi-Fi just dies the moment you step into a stairwell. It’s all that high-density fireproof material. We’ve basically built ourselves into connectivity-proof boxes. It's ironic that our safest buildings are the ones where we are most isolated from information.
We have. And then we wonder why our "smart homes" don't work. But back to the "hop limit." If Daniel wants to go even deeper—say, five or six stories—he really needs to minimize the number of devices. Can he use a directional antenna? There are some Android-compatible Wi-Fi adapters you can plug in via OTG that have external antenna ports. If you could put a Yagi antenna on the top phone pointing down the stairs, you might be able to skip three floors in one go.
Now you’re getting fancy. But if we’re talking "spare devices," we have to assume we’re using the stock hardware. I think the "staggered" approach you mentioned is the real winner. You don't need a directional antenna if you’re only going ten meters to the next landing. You just need a clear path for the waves to bounce. It's about working with the physics of the building rather than trying to brute-force through it.
True. And we haven't even mentioned the "interference" of humans. A human body is basically a big bag of salt water, which is excellent at absorbing two-point-four gigahertz signals. If the stairwell gets crowded with people, your mesh network is going to tank. I've seen this happen at conventions where the Wi-Fi works great in the morning and then completely dies the second the doors open and the floor fills up.
"Get out of the way, you’re blocking my packets!" Yeah, that’s going to go over well in an emergency. But seriously, it’s a factor. If you’re testing this in an empty building and then fifty people show up, your "two bars" of signal might drop to zero. You have to place these phones high up. Above head height. Tape them to the ceiling of the landing or the top of the door frame. This keeps the signal path clear and also makes them less likely to be messed with.
That’s a great practical tip. Keep the Fresnel zone clear. The Fresnel zone is that elliptical area around the line of sight between two antennas. If you obstruct that, even partially, you get diffraction and signal loss. Keeping the phones high up keeps the signal "path" above the people and away from most of the heavy machinery or metal lockers that might be at floor level.
I’m thinking about the "Takeaways" here for anyone who actually wants to try this. It’s not just a "fun experiment," it’s a genuine tool. Number one: Serval Mesh or Meshrabiya for the software side if you want "real" mesh. Number two: NetShare for the "daisy chain" approach if you just want internet access. Number three: One hop per floor, placed high up, and plugged into a power bank. What would you say is the absolute max number of phones before the latency makes it unusable?
Seven is the absolute breaking point. At seven hops, your handshake protocols will start timing out. The device at the bottom will send a request, and by the time the response gets back through all those "turns" and processing delays, the browser will think the server is dead. Keep it to four or five if you want to actually do anything more than send a text.
And number four: Don't expect to game or stream 4K. This is for the essentials. If you can get a stable two megabits at the bottom of a four-story hole, you’ve performed a minor miracle. You're basically building your own private ISP out of pocket lint and old glass.
It’s funny, we spend all this time talking about "cutting-edge" 6G and satellite internet, but sometimes the most "advanced" solution is just a clever way to use a five-year-old phone. It’s about being "technically literate" enough to see the potential in the junk drawer. These phones are essentially small Linux computers with built-in UPS batteries and high-end radios. We should treat them with more respect.
I’m actually going to go home and try this in my basement. I want to see if I can get a signal through my workshop floor using a couple of old Moto Gs. I've got a thick slab of concrete down there that usually kills everything. If I can get a message through using a relay on the stairs, I'll consider the experiment a success.
Just make sure you label them. Otherwise, your family is going to find random phones taped to the ceiling and think you’ve finally lost it. Or worse, they'll think you're setting up some kind of elaborate surveillance rig.
"No, honey, it’s a waveguide! I’m optimizing the Fresnel zone!" Yeah, that’ll go over great. But honestly, if it works, it’s a great "emergency drill" to run. Knowing how your house or your building handles these "hops" gives you a massive advantage if the primary network ever goes down. You start to see the architecture not as a barrier, but as a series of bounce points.
It’s about building "resilience." We talk about this in the context of the "Bunker Internet" or "Portable Enterprise Networks." Redundancy isn't just about having two of everything; it’s about having a "Plan B" that uses completely different physics or hardware than "Plan A." If the fiber line is cut and the cell towers are congested, the "Android Relay" is your Plan B. It's independent infrastructure.
And Plan C is probably shouting through a vent, but the Android Relay is definitely more "My Weird Prompts" style. Before we wrap this up, I want to make sure we gave Daniel a clear answer on the "how many hops" question. We said five is the sweet spot, seven is the limit.
Three hops for "good" internet. Five hops for "functional" data. Beyond that, you’re basically just sending a "ping" and hoping for the best. And for placement, it’s "stairwell landings, high up, sixty-five dBm signal minimum." If you see the signal dip to -80 dBm, you're going to see massive packet loss.
Perfect. Short, sweet, and subterranean. This was a fun one. It really makes you look at that old phone in your drawer as something more than just a backup camera or a dedicated Spotify player. It’s a node. It’s a piece of a larger puzzle. It's a lifeline waiting to be activated.
Every device is a node if you’re brave enough. And if you have enough rolls of duct tape.
That should be your catchphrase, Herman. Anyway, that’s our deep dive into underground Android mesh networking. Thanks to Daniel for the prompt—it’s always a treat to dig into these "edge case" scenarios that force us to rethink the hardware we take for granted.
Huge thanks to our producer, Hilbert Flumingtop, for keeping the gears turning behind the scenes. And a big thanks to Modal for providing the GPU credits that power the generation of this show.
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You can also find us at myweirdprompts dot com for the full archive and all our social links. We’re on Telegram too if you want to get notified the second a new episode drops. We might even post some photos of our own "stairwell mesh" experiments there.
This has been My Weird Prompts. Keep those phones charged, your pings low, and your hardware out of the junk drawer.
See you in the next one.
