MultiNav Pro+ BLE - does the RF front-end need any external matching components?

The RF front-end on the MultiNav Pro+ BLE is already matched to 50 ohms internally, so you don't need to add an external Pi network - just make sure your trace from the module to the antenna connector is a properly impedance-controlled 50 ohm microstrip and keep it as short as possible. Where people tend to lose range is sloppy PCB routing or using a cheap u.FL connector with high insertion loss, not the matching network itself. If you're hitting that 50km spec in the field you'll want to pay way more attention to your ground plane and antenna placement than the matching circuitry tbh.

@Robert Miller good question, and it's exactly the right thing to be thinking about before you commit your layout.

 

The MultiNav Pro+ is designed to be a complete RF front-end — the amplifiers, matching, and filtering are all handled on-module, so you're not expected to drop a Pi network between the module output and your antenna connector. The 50km spec is drone-to-drone with both units elevated (ground reflections eliminated), so the RF chain on the module itself is already optimized for that. What you do need to get right on your end is the transmission line from the module's antenna port to your connector — keep it as short as possible, maintain 50 ohm impedance on that trace, and avoid any stubs or right-angle bends near the RF path.

 

The thing that kills range in these integrations more often than matching issues is ground plane discontinuity under the RF trace and nearby copper pours that aren't properly stitched. If you post your layout I'm happy to take a look, or hit up the Dev Hub resources section — there's documentation in there that should give you the antenna interface specifics you need.

Yeah Robert's spot on about the ground plane being the real killer - I fried my first prototype's range by running a via farm too close to the antenna keepout zone and lost like 40% of my link budget before I even figured out what was happening. Also double-check your u.FL to SMA pigtail if you're using one for testing, those cheap ones from aliexpress can add more loss than you'd expect and have you chasing ghosts in your layout.

Both Roberts nailed it - the module handles its own matching so don't overthink that part. One thing I'd add is if you're doing benchtop testing before you have your final antenna mounted, throw a 50 ohm terminator on the port instead of leaving it open, saves you from misreading your link performance numbers when you're still iterating on the layout.

Solid advice all around - one more thing worth mentioning is that if you're using an SMA edge connector make sure you're soldering all the ground tabs down properly, had a board once where two of the four tabs weren't making good contact and I was scratching my head over a 6dB hole in my link budget for way longer than I'd like to admit. The module really does take care of the matching side so once that's ruled out it's almost always a mechanical/grounding issue on the connector.

Jumping in late but one more gotcha to add - if you're using a 2-layer board instead of 4-layer, double check your microstrip width calc because the thicker substrate changes your 50 ohm trace width significantly and a lot of people just copy a trace width from a 4-layer reference design without recalculating. Lost a weekend to that one myself.

Thomas that 2-layer gotcha is real - I'd also add that if you're using JLCPCB or a similar budget fab, double check their actual delivered dielectric constant matches what you used in your calc because I've seen Er vary enough between batches to shift your 50 ohm width by half a mm or more, which is a lot when you're trying to keep everything tight near the antenna keepout.

Piggybacking on Linda's fab tolerance point - if you're using KiCad's built-in trace width calculator, cross-check it against an online Saturn PCB toolkit calc because I've caught small discrepancies between them that actually mattered once I was pushing for a clean 50 ohm match. Also worth measuring your actual board thickness with calipers when the PCBs arrive since I've gotten boards from budget fabs that were 10-15% off nominal, which throws your Er-based calc off before you even factor in the Er variance Linda mentioned.

Good callout Jennifer - I've started keeping a little spreadsheet where I log the measured thickness and trace width from every fab run so I can build up a picture of what each fab actually delivers vs nominal, saves a lot of head-scratching on future boards. The Saturn toolkit cross-check is a habit I picked up after a painful experience and I won't skip it now even when I'm in a hurry.

Thomas that spreadsheet idea is solid, I started doing something similar after a bad run where I just assumed the board house would hit nominal and paid for it. One thing I'd add to the original question though - the MultiNav Pro+ does have an integrated matching network to 50 ohm so you shouldn't need an external Pi network, just a clean 50 ohm feedline from the RF pad to your connector and you're good, though all the trace width caveats everyone's mentioned still absolutely apply to that feedline.

Michael's got it right on the integrated matching - just to add a quick sanity check step though, when you get your first boards back it's worth doing a quick VNA sweep on the feedline before you populate anything else, saves a ton of debugging headache if something's off with your fab's actual stackup vs what you designed for.