Hi,
I am designing a PCB for my sensor and the board will carry a Moteino R6. I plan on using a coil antenna.
The Moteino will be mounted above the carrier board by 3 to 5 mm.
My question is: Does anyone know how far or if I should extend the ground plane of the carrier board under the Moteino?
On on hand it seems like it might act as a ground plane for the antenna to "push" against.
On the other hand it is a few mm away from the radio ground plane and only connected through the Moteino ground pin so it might be a destructive influence.
Any insight would be appreciated.
Thanks
John
Experts can chime in here, but, assuming that you're connecting your antenna to the Moteino board directly, then I wouldn't expect an additional ground plane under the Moteino board to have a measurable effect on the RF signal. The only condition I can think of that might have an effect is where your antenna extends beyond the Moteino (in the same plane) and the Carrier Board ground plane is beneath it.
BTW, there are three ground pins on the Moteino board although the ground pin near the antenna connector isn't used very often.
Tom
Hi John, I suspect you would see little improvement in signal strength by adding a ground-plane under (or over) the Moteino.
Felix already has one under the radio.
Also, in order to have much effect on the range, the ground-plane will require a very good connection to the radio ground.
A single ground connection, far from the antenna will have almost no effect (for example).
Improving on the supplied straight-wire antenna involves some work.
Consider things like straightening your coiled antenna, lowering bandwidth, more power, directional antennas, etc.
Good luck,
AE5HQ
or you could go with a PCB dipole connected with a short coax jumper:
https://lowpowerlab.com/forum/rf-range-antennas-rfm69-library/alternative-pcb-dipole-designs-(433-868-and-915mhz)/
Mine works on 915mhz on my personal weather station outside roughly 175 feet from the house.
Brian, K9BPS
Thanks to all for the replies :)
Actually distance is not my issue, I wanted to extend the ground plane partially under the Moteino for ESD capacitors for input protection. I kind of knew the ground plane connection to the Moteino would be useless but I was worried about causing a negative impact.
Thanks for the insight.
John, I'm not sure what ESD capacitors are but,
assuming that you stay a reasonable distance away from the antenna itself,
you can expect little change in radio performance by extending your
pcb under (or over) the Moteino pcb.
Good luck