GPS Antenna Open

NMEA ANT sentence shows $GPTXT,01,01,01,ANTENNA OPEN*25

What does it mean? Is there no antenna? Or is it not connected electrically? Or is not turned on programmatically?

This is on Bangle.js 2? I don't really know I'm afraid - you'd have to look at the datasheet. They do all say that though

$GPTXT,01,01,01,ANTENNA OPEN*25

I guess that an open antenna detection must be implemented in additional hardware, which may not be there in Bangles.

Hi Gordon, I cannot find datasheet for SMA Q3. Do you have one?
If you have disassembled watch, did you see an antenna there?

If you have disassembled watch, did you see an antenna there?

Yes - of course!! You can even see it in the KickStarter video

Info is at https://www.espruino.com/Bangle.js2

GPS is AT6558, datasheet http://www.icofchina.com/d/file/xiazai/2­016-12-05/b1be6f481cdf9d773b963ab30a2d11­d8.pdf

AT6558 datasheet tells that a passive or active antenna can be connected. Statuses are:
Open - no current
OK - normal current
Short - high current

My understanding it applies to active antennas that consume power.
I am not sure if some significant current can go through a passive antenna. My understanding is that a passive antenna cannot work as a resistor type load, may be it may work as a inductive/capacitive load for high frequency AC current.
The document does not tell if the chip can recognize a passive antenna, is it connected or not.
I hope a passive antenna is connected.

I've found interesting article. https://www.u-blox.com/sites/default/fil­es/products/documents/GNSS-Antennas_AppN­ote_%28UBX-15030289%29.pdf
It states that all antennas have 50 Ohm impedance.
But AT6558 does not look like measures impedance, it rather measures DC current in VANT_IN - ANT_BIAS chain. With a passive antenna that current should be 0A.
In AT6558 datasheet Figure 9-2 "passive antenna scheme" shows active antenna with LNA.
Also it says:
10.1 Active Antenna Feed and Detection
The following figure, the chip active antenna detection circuit can detect the state
of the active antenna

So, I think Antenna Open status is normal for a passive antenna.