NT1065_USB3 GPS L1 not detected

[Hamada2you]

Hello everyone,

I'm seeking assistance with the nt1065_USB3 GNSS receiver manufactured by ntlabs. I've been facing difficulties despite my efforts to make it work properly. Here's a breakdown of my setup and the challenges I'm encountering:

Hardware:

• Active antenna: Link to active antenna
• GNSS_S14 splitter: Link to GNSS_S14 splitter

Setup: I have connected the active antenna to the GNSS_S14 splitter provided by ntlab, and then connected it to the CH1 input of the nt1065_USB3 receiver using the "config_1.hex" configuration file.

Issue: Unfortunately, I have been unable to detect any L1 signals or satellites despite my efforts. I have tried various active antennas, but the situation remains unchanged.

Successful Test: I did manage to perform a signal tone RF input test, where I input a single tone signal at 1575.42MHz with low power input, and I was able to observe the signal in the output.

I would greatly appreciate any insights or guidance on how to resolve this issue. If anyone has experienced a similar problem or has expertise with the nt1065_USB3 GNSS receiver, your assistance would be invaluable.

Thank you in advance for your help and suggestions.

 

[rjenkinsgb]

What is the full model number of the splitter & which satellite service are you trying to receive?

From the S14 data sheet you linked, it could have any band filter provisioned for any output (depending on the full part number), so you need to match the band of the service you want to the correct output socket?

I've never used those, only various conventional singe-antenna type GPS / GNSS modules.

 

[Hamada2you]

What is the full model number of the splitter & which satellite service are you trying to receive?

From the S14 data sheet you linked, it could have any band filter provisioned for any output (depending on the full part number), so you need to match the band of the service you want to the correct output socket?

I've never used those, only various conventional singe-antenna type GPS / GNSS modules.

The splitter enables us to connect the active antenna and obtain complete GNSS Band 4 RF outputs. It is then connected to the nt1065_USB3, which has 4 RF inputs (4 channels). These channels are configured to detect the specific band you are interested in, in this case, the GPS L1, which is configured in CH1. The only available document related to the splitter is the on I attached in previously.
nt1065_USB3 board : nt1065_USB3 Evaluation Kit.

 

[Nigel Goodwin]

Issue: Unfortunately, I have been unable to detect any L1 signals or satellites despite my efforts. I have tried various active antennas, but the situation remains unchanged.

Are you doing these tests indoors or outdoors?

 

[rjenkinsgb]

The only available document related to the splitter is the on I attached in previously.

The splitter itself must have a full part number on it, surely? eg.
BS14-????

If it's BS14-2xxx or -3xxx then the GPS L1 is on output 1; if it's anything else, you will not get the signal on that connector.

Also, have you tried the antenna direct, rather than via the splitter? I'd expect it to work, just be more prone to interference.

 

[Hamada2you]

Are you doing these tests indoors or outdoors?

all done outdoors

 

[Nigel Goodwin]

all done outdoors

Good, because they don't usually find any satellites at all indoors.

 

[Hamada2you]

The splitter itself must have a full part number on it, surely? eg.
BS14-????

If it's BS14-2xxx or -3xxx then the GPS L1 is on output 1; if it's anything else, you will not get the signal on that connector.

Also, have you tried the antenna direct, rather than via the splitter? I'd expect it to work, just be more prone to interference.

The test I conducted took place during clear sky conditions in the middle of the day. I used two different active antennas: Active Antenna 1 and Active Antenna 2. I successfully operated the splitter and connected Channel 1 of the splitter to Channel 1 of the nt1065_USB3 receiver to receive the GPS L1 signal. The figure below illustrates the output that I obtained:

No satellite detected.

I can not connect the antenna directly. In order to meet the receiver's requirement of at least 15 dB gain before input, the splitter serves the dual purpose of an active antenna DC feeder and splitter. It provides the necessary gain to amplify the signal before it reaches the receiver.

 

[rjenkinsgb]

The figure below illustrates the output that I obtained:

I do not understand how you can say "successfully" if it's not receiving anything?

How did you obtain the signal plot? That's scaled 0-25 MHz, which has no correlation to GPS / GNSS operating frequencies.

Also, what's the longest you have left everything connected and active?
From a "cold start", eg. the first time a GPS receiver is used, or used at a new geographic location, it can take anything up to 15 minutes or more to find any satellite signal, then download and start to update it's Keplerian element (orbital calculation) database, so it can search for the specific frequencies of satellites that should be above the horizon in its present location.

 

[Hamada2you]

I do not understand how you can say "successfully" if it's not receiving anything?

What I meant was that I fixed the main splitter issue. The problem was that the active antenna was not working, resulting in no output signal. Upon investigation, I discovered that the active antenna feeder line (+3v) in the circuit was not connected. I resolved the issue by connecting the feeding line properly, thereby providing power to the active antenna and allowing the splitter to work. Previously I was not able to get any output.

How did you obtain the signal plot? That's scaled 0-25 MHz, which has no correlation to GPS / GNSS operating frequencies.

The nt1065_USB3 receiver utilizes a 2-bit ADC operating at a sampling rate of 53MSps to digitize the incoming signal. Prior to the digitization process, a local oscillator at 1590MHz is employed to downconvert the GPS L1 frequency (1575.42MHz) to an intermediate frequency (IF) of 14MHz. This downconversion allows for effective sampling of the signal at a rate of 53MSps.

Also, what's the longest you have left everything connected and active?

The receiver has the capability to save a binary file containing the sampled GNSS data. I intend to use this data in my post-processing code, which is designed to detect satellite visibility based on a 1ms data interval.