How to increase sensitivity of EM-406?

GPS/GNSS Development Boards
1

Hi - I had really hoped to be able to use my EM-406 indoors - but I’m finding that in about 95% of indoor situations it does not work. I am feeding it a good, clean 6V supply voltage. It just has the worst trouble getting a lock.

Any suggestions for increasing its range? Would a ground plane below the module help?

2

You need a GPS that is designed to work indoors, u-blox makes them.

Leon

3

leon_heller:
You need a GPS that is designed to work indoors, u-blox makes them.

Leon

My understanding of the EM-406 is that, as it uses the sirfstar III chipset, it should work indoors.

Either way - sometimes it does work - so I figure if I can just improve it some, I should be mostly OK.

What u-blox modules do you reccomend for this app?

4

LEA-4S SuperSense is claimed to be suitable for indoor use. I haven’t tried it, I’m using the LEA-4A.

Leon

5

Are you using your em406 using a bread board or an a dedicated pcb? I found it difficult to get a long when running power via wirewrap to the em406 using SFE’s serial breakout board. When I tied the em406 to the actual circuit thing work fine. I generally need to be in a room with a window to maintain a good lock.

6

ohararp:
Are you using your em406 using a bread board or an a dedicated pcb? I found it difficult to get a long when running power via wirewrap to the em406 using SFE’s serial breakout board. When I tied the em406 to the actual circuit thing work fine. I generally need to be in a room with a window to maintain a good lock.

I have it connected to a PCB via the cable, but I don't have it sitting on top of the PCB.

I have heard that having a ground plane beneath it helps out alot. If I were to ground the aluminum frame, would that help it? Or anything else I can do?

Thanks!

7

I think the leads connecting to your servos may be causing the problem. I am not an RF expert by any means. My pcb does have a large ground plane on it. Overall nice looking design and great machining! Just curious but what are you using the MicroSD slot for?

8

ohararp:
I think the leads connecting to your servos may be causing the problem. I am not an RF expert by any means. My pcb does have a large ground plane on it. Overall nice looking design and great machining! Just curious but what are you using the MicroSD slot for?

Hmm there's a good 2-3cm or so on each side of the GPS from the servos and their connectors - you really think that that could be causing the problems? How could I fix that?

The machining was actually done by a friend of mine - I designed all the parts in Autodesk Inventor, then he milled them out for me.

The MicroSD is for data logging. I haven’t gotten around to implementing this feature yet - but my plan is to log all events. That includes all wireless data coming in, gps data, compass data, accelerometer data, gyro data (when I get my new board made), all collisions detected, onboard voltage monitoring data, all timestamped with the onboard RTC.

9

I was using http://melabs.com/products/labx1.htm and the SFE serial cable breakout board. I used power (4 wire wrap lines) and comm from one board to the other. I noticed that I could never get a lock indoors or out. Whenever the two were seperated there were no problem getting a lock. I finally decided that the wire wrap powerlines were the problem. Your design may require that you mount the em406 further away from the base of your bot. Sorry I can’t help you more. Good luck with your project.