GNSS2 highly susceptable to RF noise

Support GNSS
1

Hi there,

We are currently using a GNSS2 module connected via CAN on one of our aircraft, and it seems highly susceptible to environmental noise. You can see from the graphs that there are two GPS on the aircraft, one being a ZED-F9P, and the other being the Zubax GNSS2. At certain locations, the Zubax will loose all satellites, but when moved away from the location, it will regain satellites. This has been tested on the ground, and in the air.
Ground:

GPS2%20Issues
GPS2%20Issues1200×600 44.9 KB

Air:
I can only upload one image at a time.

This is being flown in proximity to high power RF, in the following frequencies:
FM Radio (88-108MHz),
VHF TV (170-230MHz) and
UHF TV (470-700MHz)

We can see that the ZED-F9P is not affected by the RF source, but the GNSS2 is completely killed at certain points.

When flying in non high power RF environments, the GPS has performed exactly as expected.

When flying with other GPS modules, specifically of the M8* variants, we have not noticed this in the past.

I can provide full logs from the flights, please PM me if you need these.

Is there anything we can do see what the issue is short of replacing the unit and testing again?

All setting are stock on the GNSS2, aside from the CAN Node ID.

Best Regards,
Anton

2

Hey Anton,

Can you please try attaching the other image again?

Please tell us the hardware version of the GNSS (it is written on the PCB like v2.3). It might also help if you told us the unique ID of the units where you observe this behavior.

Thanks!

3

Hi Pavel,

It is slightly awkward to get the serial number, as it is currently with a customer, and not easily viewed with standard tools. I presume these are not recorded in APM logs per chance?

We have had two batches from you, and I am unsure which batch it came from. However it was either a version 2.2 or 2.3. Leaning towards version 2.2, as the old stock would probably have been pulled first. If need be I can get the customer to pull apart the GPS housing and check.

Here is the second image:

GPS2%20Issues2
GPS2%20Issues21200×600 42.1 KB

Best Regards,

4

If it’s v2.2, then you are probably affected by this issue: New GNSS failure to get gps fix - #4 by pavel-kirienko. We had a large number of units affected by defective low-noise amplifiers with integrated SAW filter ICs provided by Qorvo Inc. There was a lengthy debate with them about the nature of this failure which led to nothing, so we switched to a new supplier and released v2.3, where the entire analog front-end is built on high-reliability AEC-Q 100 grade 2-qualified components. We have had no issues reported since then.

After v2.3 was released, we replaced several hundred units for the affected customers upon request. I suspect that the unit in question is an old v2.2 which was never replaced. If you could confirm its version number we could ship you a replacement v2.3.

5

I just got the customer to pull it apart and verify the version number, it is a version 2.3.

Pictured below:

IMG_5738
IMG_57383024×4032 2.27 MB

I am just getting the unique id of the unit, will report back once that has arrived.

6

Here is the zubax_id output from the GPS

zubax_id
product_id : ‘com.zubax.gnss’
product_name : ‘Zubax GNSS’
sw_version : ‘4.1’
sw_vcs_commit: 103583050
sw_build_date: Nov 21 2017
hw_version : ‘2.2’
hw_unique_id : ‘Nf/VBVBZMTQwYSRDAAAAAA==’
hw_info_url : http://device.zubax.com/device_info?uid=35FFD50550593134306124430
0000000
hw_signature : ‘HIULzWi9wR/odYn6Gd5vFpTutQJ1xGD2RbH7vtfiVMGKmbSjjbp+kW4luKjttXRV
UsKYtqYU90de30KAqHL6Wbw28xhnv0LAAjQZfCjRAaGUqcL5iOY/s5fYEpl7ZcdHwB1hzAg7cgsCRzih
0s1s27QXTvR+aYx6XTQnEoIYdOY=’

Curiously enough the hardware_id says v2.2, not v2.3, despite the silkscreen saying v2.3. Which one would be correct?

7

The picture looks as if there are some metallic shavings on the edges of the device, but it’s hard to be certain.

We could ship you a new unit to see if it’s a one-off defect, possibly caused by damage to the device. We could also ship it directly to your customer if that’s more convenient. If you would like to proceed with either option, please email support@zubax.com, and we’ll have it organized quickly.