Antenna Connection Problem

Q&A forumCategory: QuestionsAntenna Connection Problem
microderm asked 3 weeks ago

I  connected my simpleRTK2Blite to the antenna and to my development board and waited for a signal. After a few minutes with no signal I checked the connections and found that the F9P was really hot, so I switched it off.
Next, I placed the simpleRTK2Blite on the Xbee USB adapter to check that it wasn’t my dev board causing problems. It still ran hot with no signal.
I checked the antenna and twisted it on much tighter than before and tried again. This time, the F9P stayed at room temperature and gave a PPS signal after about 30 seconds as expected. I checked my SMA connector and found that the pin had been pushed in!
History:
Originally, I bought the simpleRTK2B with antenna (1), some time later I bought the smaller simpleRTK2Blite with antenna (2). I starting using the simpleRTK2Blite with the original antenna (1). I found that I needed to twist it tight to get satellite data on u-center.
Prevention:
Lucky, my simpleRTK2Blite still works, but clearly, there is a risk of damaging the hardware if the antenna is not properly connected.
I read the ZED-F9P Interface Description doc, but couldn’t work out how to get antenna connection status. I noticed at startup, the F9P would report its antenna status as ok $GNTXT,01,01,02,ANTSTATUS=OK*25 even when it was not connected!
How can I determine whether the antenna is properly connected (so that I can flash a warning light when it isn’t)?
Thanks,
microderm

Ardusimple Staff replied 3 weeks ago

Hi microderm,
There was a defective batch of ann-mb that were getting shortcircuitted intermittently and could lead to the behaviour you described. If you bought this antenna from us, you can open an investigation by sending an email to info@ardusimple.com

Regarding the messages of antenna detection, this is disabled on simpleRTK2B and lite, so it will always show that antenna is OK.

microderm replied 3 weeks ago

Thanks for the info. I have the following questions:
– Why is the antenna message disabled?
– Would enabled antenna messaging solve my antenna detection problem?
– Is there some other way to test whether the antenna is connected?
Thanks,
microderm

Ardusimple Staff replied 3 weeks ago

antenna detection requires an external circuit that is not implemented on the simpleRTK2B boards to reduce cost.
as for detection of antenna connection via software, you can calculate if with message ubx-mon-hw, value AGC. Try to connect and disconnect the antenna, you will see that this value jumps between 2 numbers. Take the number in the middle to decide if antenna is connected or not.

microderm replied 3 weeks ago

Thanks for info. I set the F9P to send UBX-MON-RF messages at 2 second intervals and used the high byte of the AGC. Testing on my window ledge, I had figures of:
Antenna plugged in: 20
Antenna unplugged: 26
I’ll test again on open ground to check whether the figures are similar with greater view of the sky.
I now have a red LED come on when the antenna is not connected.
Thanks,
microderm