L76k: antenna open

IoT Modules GNSS Module
1

Good morning,
I’m trying to fix the L76K integrated on a lora gateway branded Pisces P100.

So far I’ve been able to startup the chip and get NMEA data at 1Hz (using linux gpsd).
For that I wired RESET to VCC, verified VCC=3.3V and STANDBY=High.

The issue is, I’m getting “ANTENNA OPEN” message all the time. I verified the RF_IN pin is wired to the fiberglass GPS antenna (within the specs).

I don’t have a spectrum analyzer, so I’m not sure about the PCB for the antenna. But continuity looks good: no short circuit on RF_IN, no continuity issue on the wire.

It looks like the PCB contains an impedance stage.
How can I test that the impedance is correct without a spectrum analyzer ?

This is the messages I get every second:

(32) $GNGGA,0,00,25.5,64
(44) $GNGSA,A,1,25.5,25.5,25.5,101
(44) $GNGSA,A,1,25.5,25.5,25.5,202
(20) $GPGSV,1,1,00,065
(36) $GLGSV,1,1,02,70,35,86,35,072
(27) $GNRMC,V,N,V37
(21) $GNVTG,N*2E
(17) $GNZDA,56
(33) $GPTXT,01,01,01,ANTENNA OPEN25

2

Hi

  1. Are you using an active antenna or a passive antenna?
  2. If an active antenna is used, use the VDD_RF pin to power the antenna, and measure the current of the VDD_RF pin.
  3. If a passive antenna is used, antenna detection is not supported.
3

its a passive Antenna.

Should I check that VCC_RF is not wired ? What triggers the “antenna open” message when using a passive antenna ?

I’m researching why I’m getting “antenna open”, even when I have a GPS specific antenna, I even tested another GPS antenna to make sure.

4

Hi Benjamin
Passive antennas do not support antenna detection.
When you connect a passive antenna, VDD_RF has no output current and the antenna is in an open circuit state; so the “antenna open” message will be output.
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