MultiNav Pro+ BLE - does range drop significantly in a mobile-to-mobile setup?

Yeah your gut is right to be skeptical - mobile-to-mobile with both nodes in motion and no elevated antenna is basically a worst-case scenario for range, and in my testing you can expect a pretty significant hit compared to the spec sheet numbers (which are almost always measured line-of-sight, one end stationary, ideal conditions). The 50km claim is probably doable in a balloon-to-ground type setup but realistically for two ground vehicles I'd plan around maybe 20-30% of that and tune from there.

@James Hernandez yeah your 20-30% estimate is in the right ballpark for ground vehicles, but I'd push back slightly on treating it as a fixed multiplier — the bigger variable in my experience is antenna placement on the vehicle itself, not just the mobility. If both nodes have decent vertical clearance above the roofline and you're in open terrain, you can do significantly better than that. It's when you get metal bodywork eating your pattern that things fall apart fast.

 

The 50km spec is drone-to-drone with both nodes airborne and ground reflections eliminated — that's basically the ceiling, not the baseline. For two ground vehicles the published 5km ground-to-ground figure is actually the more honest reference point, and in practice with good antenna mounts I've seen people push closer to 8-10km before link quality starts degrading meaningfully. Doppler at vehicle speeds is genuinely negligible for BLE — you're not moving fast enough for that to matter.

 

If you want to get serious about the link budget for your specific setup, the AI Firmware Builder in the Dev Hub is actually pretty useful for this — you can describe your platform geometry and it'll help you model realistic margins rather than guessing from spec sheet numbers.

Richard's numbers line up with what I saw too - we were getting roughly 12-15km reliable link between two moving ground vehicles before packet loss got bad, and that was with reasonably clear terrain. Antenna height makes a huge difference so even mounting them on roof racks vs. tucked lower on the chassis changed things noticeably for us.

Yep, Susan's point about antenna height is huge - we saw similar numbers on a rover project and honestly just getting the antenna up an extra 30cm on a mast made a noticeable difference in link stability at distance. For true mobile-to-mobile ground use I'd treat 10-15km as your realistic planning figure and budget for a repeater if your use case needs more than that.

Solid advice above - one thing I'd add is that link quality also degrades faster when both nodes are moving because you're dealing with doppler effects and constantly changing multipath, not just the geometry. We noticed on a two-rover test that even brief terrain occlusions that'd be momentary on a static link would sometimes take a few seconds to recover on mobile-to-mobile, so factor that into how tolerant your protocol needs to be.

Thomas's point about recovery time is something we got burned by early on - we ended up tuning our retransmit timeout way up from defaults because the stock settings assumed a faster link recovery than we were actually seeing on dual-mobile. If your protocol has any kind of ACK/retry logic, definitely stress test it with both nodes moving and throw in some simulated terrain occlusions before you commit to a range assumption.

All solid points above - one more thing worth flagging is that if your two vehicles are converging or diverging at any real speed, the effective link budget shifts faster than most people expect and it can make your margin calculations feel optimistic in a hurry. We basically ended up doing our range planning at the worst-case closing/opening speed we'd actually see in the field rather than treating it as a static distance problem.

Really good thread - just to add a practical data point, we ran a dual-mobile test over open farmland last spring and were seeing reliable comms drop off around 12km with both nodes at vehicle-roof height, which lines up with what James said. The 50km spec is real but that's basically best-case elevated antennas and line of sight, not two trucks bumping around a field. Definitely echo the advice to design your protocol around the pessimistic number and treat anything beyond that as a bonus.

Jennifer's 12km real-world number matches pretty closely what we saw in a similar dual-mobile setup - honestly that's the number I'd plan your whole protocol around and just be pleasantly surprised if you get more. The 50km is not a lie but it's basically a ceiling that assumes everything goes right, and in a two-moving-nodes scenario almost nothing goes right consistently lol.

Yep, 12km lines up with what I've seen too - we basically bake in a 10km "planning range" for any dual-mobile BLE work and that's kept us out of trouble. One thing I'd add is that antenna orientation matters a lot more than people expect when both nodes are bouncing around, we saw pretty wild swings just from vehicle pitch on rough terrain.

Echoing the 10-12km planning range everyone's landed on - that's basically where we netted out too after field testing. One thing that bit us early on was assuming our link margin calcs were stable when actually antenna orientation drift on rough ground was eating like 3-4dB we hadn't accounted for, so definitely worth what Michael said about that.

Solid thread - the 10-12km planning figure is exactly where we landed too after some painful lessons on a dual-mobile nav project last year. One thing worth flagging if you haven't hit it yet: we saw the orientation problem Michael mentioned get *way* worse at speed, like the link would be fine at 30kph and then degrade noticeably at 80kph just from chassis vibration affecting antenna coupling, so if your vehicles are going fast it's worth stress-testing that specifically.

Yeah the 50km spec is basically best-case line-of-sight with good antenna geometry on both ends - in a dual-mobile setup you're fighting multipath, orientation drift, and the fact that neither node is elevated, so 10-12km as your planning number is the right call. One thing I'd add to what Patricia mentioned about speed: we actually saw the vibration issue show up differently depending on how the antenna was mounted, rigid mounts transferred more chassis vibration into the connector and we were getting intermittent coupling issues that looked like range problems until we traced it back. Soft-mounting the antenna assemblies bought us back like 2dB of consistency at highway speeds.