SIM908 problem GPS antenna.

[diepvu1805]

Hi all,
I am using SIM908 to get GPS.
In my design, I connect GPS-VANT-IN(pin76) with VBAT pin(i use the active antenna). Everything run well.
But today, I cann't not get GPS. I used mutilmeter to check voltage on GPS-ANT(pin 79), it present 0V(in common, it present approximate VBAT). That mean is the external antenna not power supply.
I think the GPS part of SIM908 is died, but I cann't explain because I still SIM908 to send SMS, call...
pls, help me.
Thank you,

 

[mgdaubo]

Hi diepvu1805,

Did you use "AT+CGPSPWR=1" to power on the GPS on SIM908?

Normal profile on SIM908 have GPS module powered off.

 

[diepvu1805]

Hi diepvu1805,

Did you use "AT+CGPSPWR=1" to power on the GPS on SIM908?

Normal profile on SIM908 have GPS module powered off.

Yes, I did. and I checked voltage present on GPS_VANT_OUT(pin75) is 2.8V. but GPS not work.

 

[Echo wang]

Pls use AT+CGPSRST=1, if it do not work, then your module in GPS is down.
In SIM908, GSM and GPS are different part. If GSM part do not down, it can send SMS, call....

 

[diepvu1805]

I used AT+CGPSRST=1 to reset GPS, I still receive the data from SIM908 but data errors, it's not position.
I think GPS anttena not work because it hasn't power(GPS_ANT pin present 0V), but I haven't the solution to solve this problem.

 

[Echo wang]

It seems the GPS function is damaged, pls contact your vendor to repair it.
The guarantee is 1 year

 

[diepvu1805]

Thank all,

 

[vedagarbhamsandeep]

FYI -> most of GPS modules or rather what we manufacture (28dB LNA + 3dBi Ceramic CP antenna) require a minimum of 3.3 ~ 3.5V for operation. Please do cross check on this and also check the datasheet from your vendor.

I do not have thorough knowledge on SIM908 module though.

 

[diepvu1805]

FYI -> most of GPS modules or rather what we manufacture (28dB LNA + 3dBi Ceramic CP antenna) require a minimum of 3.3 ~ 3.5V for operation. Please do cross check on this and also check the datasheet from your vendor.

I do not have thorough knowledge on SIM908 module though.

As follow SIM908's datasheet(5.3):"If the antenna's is not 2.8V, a proper voltage be provide to the GPS-VANT-IN depending on the active antenna...". I am using the GPS antenna with voltage supply from 3 -5V, thus I connected GPS-VANT-IN pin to VBAT. The voltage GPS-VANT-IN rate didn't write in the SIM908's datasheet.
pls, suggest me the best solution. I should connect GPS-VANT-IN pin to 3.3V or VBAT(4,4 - 4.6V). They are ready voltage in my design.
Thank,

 

[Echo wang]

As follow SIM908's datasheet(5.3):"If the antenna's is not 2.8V, a proper voltage be provide to the GPS-VANT-IN depending on the active antenna...". I am using the GPS antenna with voltage supply from 3 -5V, thus I connected GPS-VANT-IN pin to VBAT. The voltage GPS-VANT-IN rate didn't write in the SIM908's datasheet.
pls, suggest me the best solution. I should connect GPS-VANT-IN pin to 3.3V or VBAT(4,4 - 4.6V). They are ready voltage in my design.
Thank,

Both of them are ok, I prefer 3.3V

 

[Amalinda]

I understand using a GSM Active antenna in SIM908 is not possible. is there anyway that I can fix a small amplifier before the GSM antenna so my weak GSM antenna signals are amplified?
I would so much appreciate..

 

[embRTS]

Practically You can power it by typical 3.7 V also