3 ms·

I'm not very familiar with Freifunk, but if it interfaces like a normal WLAN to the user, then simply not advertising SSID and a basic password will go pretty f

by mNovak 4y ago

I'm not very familiar with Freifunk, but if it interfaces like a normal WLAN to the user, then simply not advertising SSID and a basic password will go pretty far. This is obviously not secure against any sort of special operative, but eliminates it as a very easy convenient tool for e.g. a mobik with a cell phone, if this finds its way anywhere near a frontline. An upside of highly directive, P2P links is that they can provide some protection against EW, simply by nature of having a constrained field of view. Also I'll note most consumer devices (laptops, cell phones) have pretty bad antennas, they're assuming you have a router right nearby. You might get much better coverage if you're also able to provide the user with a simple USB dongle that can attach to an external antenna (e.g. a 10dBi yagi-uda) If there is need for any input on the antennas side, I'm more than happy to help (EM PhD, design antennas for a living). 2.4GHz is relatively forgiving, you can literally hand make antennas, with some attention to detail. If you have access to shipping (I really don't know the situation) they can be mass produced on PCB.

namibj 4y ago
While not sure if it will help/matter for the OP, I'd like to confirm the idea/thought of using (ground-plane-having-for-back-lobe-suppressing) axial-firing helix antennas, in pairs, to do circular polarization MIMO on the point-to-point long-distance links. So one clockwise and one counter-clockwise helix, connected to the two antenna ports on a cheap 2.4 GHz router. Gain seems to max out around 15 dBd, in that case, for a 90cm long antenna of ~5cm diameter. The beauty of circular polarization there is the independence of mounting angles/matching rotations, but I guess a small forest of H/V dual-polarization Yagi's (or, for routers with 3X3 MIMO, 3 equally-spaced polarization directions, assuming that works without breaking the workings of the Yagi) might be easier due to the potential for a solid metal center pillar to hold the elements. A forest instead of a lone Yagi would be to increase gain more efficiently than by merely elongating a single Yagi, as the latter would quickly cause mechanical issues in wind. I'm imagining access to an improvised spot welder to attach lengths of copper wire to a steel support pillar, then finished with some paint as an anti-corrosion coating. Or some more low-tech attachment process, like a styrofoam pillar with the wires pierced through in the right spots, mounted either indoors or in a drain pipe or such for weather protection. Can you confirm that these approaches are appropriate for the situation/call some out that are not appropriate?

by mNovak 4y ago

namibj 4y ago

While not sure if it will help/matter for the OP, I'd like to confirm the idea/thought of using (ground-plane-having-for-back-lobe-suppressing) axial-firing helix antennas, in pairs, to do circular polarization MIMO on the point-to-point long-distance links. So one clockwise and one counter-clockwise helix, connected to the two antenna ports on a cheap 2.4 GHz router. Gain seems to max out around 15 dBd, in that case, for a 90cm long antenna of ~5cm diameter. The beauty of circular polarization there is the independence of mounting angles/matching rotations, but I guess a small forest of H/V dual-polarization Yagi's (or, for routers with 3X3 MIMO, 3 equally-spaced polarization directions, assuming that works without breaking the workings of the Yagi) might be easier due to the potential for a solid metal center pillar to hold the elements. A forest instead of a lone Yagi would be to increase gain more efficiently than by merely elongating a single Yagi, as the latter would quickly cause mechanical issues in wind. I'm imagining access to an improvised spot welder to attach lengths of copper wire to a steel support pillar, then finished with some paint as an anti-corrosion coating. Or some more low-tech attachment process, like a styrofoam pillar with the wires pierced through in the right spots, mounted either indoors or in a drain pipe or such for weather protection. Can you confirm that these approaches are appropriate for the situation/call some out that are not appropriate?