Hi guys, I have a NEO-M9N with a chip antenna. Works OK but takes ages to get lock and drops out easily. I was wondering if it’s possible to desolder the chip antenna and solder pigtail with a connector for a better antenna. I have no worries actually being able to do it but not sure if it will work as antenna design is a bit of a black art to me.
Stu.
Hi Stu,
With some careful soldering, it’s certainly possible to replace the antenna with a u.FL or SMA pigtail. BUT - there’s a catch… The pigtail connection won’t provide the bias voltage for an active antenna. And an active antenna without bias voltage will give you close to zero signal… For best results, you’ll need to connect a passive GNSS antenna. In a pinch, a passive Iridium antenna would do - as the GNSS L1 and Iridium bands are close together.
Or, with more careful soldering, you could add the R, L and C bias circuit you see on our regular u.FL / SMA boards…?
Take good ESD precautions too - you don’t want to accidentally zap the module’s RF input.
I hope this helps,
Paul
Thanks for the info, Paul. I was thinking of using the GPS-15246 antenna as the end goal is a wearable GPS tracker to track my son’s sprint training. When I look at the schematics for the NEO-M9N board with UFL antenna I see an inductor, resistor and capacitor but for the chip antenna there’s none of that. Will it make a huge difference? Can I simply snip the UFL connector off the end of that antenna and solder it directly to the PCB (with some strain relied, of course)? BTW, how does the polarity on that antenna correspond with the traces on the PCB I’d be connecting to?
Hi Stu,
The GPS-15246 Molex antenna is passive, so you wouldn’t need to add the extra RLC bias circuit. Carefully cut off the u.FL connector. Strip back the black outer insulation of the coax cable to reveal the braided shield. Tease the shield apart and twist it into two ‘wires’, one on each side. I usually use a needle to help unpick the braid. Strip off a small piece of the clear/white insulation from the center conductor. Quickly ‘tin’ both shield wires and the center conductor with solder. Be quick - you don’t want to melt the insulation. Desolder the chip antenna - or carefully cut through the curved RF track that connects it to the u-blox module. (Make two cuts, about 0.5mm apart, then carefully cut out the piece of copper in between to create a small gap.) (Cutting the track is the best option. You can solder over the gap to re-connect the chip antenna if you need to.) Scrape off a small patch of the red solder resist from the RF track. Do the same on the GND copper on either side of the RF track to create two GND pads. Tin all three. Quickly solder the center conductor to the RF track, and the two shield braids to the two GND pads. Test. Then secure with glue / tape.
The antenna is adhesive. It is OK to stick it to a plastic enclosure, but don’t stick it to metal or anything connected to GND. Don’t stick it to your battery pack either. It needs to be in ‘free space’ - well away from conductive ground planes. If you do stick it to anything conductive, you’ll get zero signal… (I’ve done exactly that. I stuck it to my LiPo battery. Took me a while to figure out what I’d done wrong.)
Your mileage may vary. Proceed at your own risk. And all the other usual disclaimers… But this should get you going.
All the best,
Paul
Wow, thanks for the super detailed info, Paul! Will that antenna be OK against someone’s back (not in contact with skin of course, but stuck on a shirt)?
cheers,
Stu.
Hi Stu,
All I can say is that it works OK when attached to a dog…! I had the GNSS and Molex antenna in a plastic waterproof case attached to the dog’s harness. The antenna was upward-pointing though.
Good luck with your project - sounds great! Let us know how it goes,
Paul