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Forum Index : Microcontroller and PC projects : NEO-7M Dual Antenna
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Azure Guru  Joined: 09/11/2017 Location: AustraliaPosts: 446 |
I have not been having any luck getting this NEO-7M-0-000 module to be able to lock on. Here is a link to the module in question eBay NEO-7M Module After no success with it connected to MMBPv2, I tried it directly connected to PC through a USB->Serial adapter and also through the direct USB port that is on module. MMBPv2 communicates with it and can communicate via TT and u-center 8.27. There is no problem talking to the module just can't get it to lock onto to any more than 1 satellite only occasionally, even when outdoors. This leads me to suspect the antenna or input side of things. I have also tried a V-KEL module with built in ceramic antenna and it works perfectly both indoors (within reason) and out. My conclusions are that location is ok for reception and able to communicate with GPS module ok. I only have 1 x NEO-7M module and 1 x V-KEL module at the moment. It has a built in ceramic antenna on one side and a socket for an external SMA antenna. I was wondering if there is anything you need to do to make it use the ceramic antenna and disable the external input. I do not have an external antenna to try and have not soldered the socket on (which ships separately). It looks like the Ext Connector is wired directly to Ant input pin on NEO. Cannot see where ceramic antenna is wired to. It may be as simple as adding a link between the ceramic input and ext input. Have not been able to locate a schematic on this module although it does appear very similar picutre I have seen of a dual antenna (not compact) version of some NEO-6M modules. Hopefully someone with more expenrience on GPS modules might be able to give me some suggestions. |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
I have seen boards where the ext antenna connector is just placed on the track between the ceramic antenna and the module RF input. And worse still the ceramic antenna is not switched out when an external antenna is connected. Is the external antenna connector an IPX connector? |
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| Azure Guru Joined: 09/11/2017 Location: AustraliaPosts: 446 |
The connector is SMA as shown in the ebay pictures. Did a little more deciphering of the PCB module. The external antenna appears to route directly to 3 points. 1. Ext Antenna trace to Neo 7M RF in pin. RF in connection to Ext Antenna. 1. Ext Antenna trace to inductor to a 10R resistor to Vcc RF. Active antenna bias. 2. Ext Antenna trace via cap to LNA output. AC decoupled output of LNA to RF in. The internal antenna goes through a cap and inductor (all in series) and onto the input of the LNA (very small 6 pin IC). Other pins on the LNA go to gnd and vcc, Enable pin is pulled high. It seems to match pinout of a BGU7008, unable to identify actual part number. Lots of ground stitching on either side of both antenna traces to stop intereference and hopefully match impedance. So, result is internal antenna goes through an LNA is AC decoupled and goes to RF in at same time as external antenna which is also biased for active external antenna. Without the external antenna connected it should work fine. Don't have any gear to test output of LNA. Need to add a spectrum analyzer to my test gear to test this $10 part :) Anyone have any suggestions (RF is not one of my strengths)? |
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| srnet Senior Member  Joined: 08/08/2014 Location: United KingdomPosts: 164 |
Connect the GPS to a USB-Serial adapter and download the Ublox Ucentre application. This application will, in graphical form, tell you how many satellites the GPS can see and their signal strengths. You need around 4 satellites above circa 27dB to get a valid fix. You can get the same information from the GPGSV sentences if you know how to read them. $50SAT is Silent but probably still working. For information on LoRa visit http://www.loratracker.uk/ |
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| Azure Guru Joined: 09/11/2017 Location: AustraliaPosts: 446 |
@srnet Thanks for the suggestion. As mentioned in my first post I have tried that already. I can read the GSV codes and one is sent for each of the satellites found and the module only finds 1 occasionally. My problem is the not communicating with the unit but the unit not finding satellites, therefore and antenna or receiver issue. |
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| srnet Senior Member Joined: 08/08/2014 Location: United KingdomPosts: 164 |
The Ublox GPSs are very sensitive to static causing damage to the antenna input. At least that's the case for the Ublox 8s, I have damaged a few ranging from no satellite reception at all to barely working. There needs to be protection on the antenna input, its mentioned in the data sheet, but I have seen modules without this protection fitted. $50SAT is Silent but probably still working. For information on LoRa visit http://www.loratracker.uk/ |
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| Talbit Senior Member Joined: 07/06/2011 Location: AustraliaPosts: 210 |
It's a few years now but have you had any success with your NEO-7M modules? I'm having the same problem. Talbit |
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