RTK Express Plus no GPS Signal

GPS/GNSS Enclosed Products
1

We have a customer with a Sparkfun RTK Express+ unit that is showing no satellites in range while connected to the antenna.

They have tried the following:

  • change antenna cable
  • factory reset over wifi connection
  • We tried updating the firmware using this .bin file The user interface freezes when attempting to use this file to update the firmware. As a result, we did not update the firmware.
  • Disconnecting and reconnecting the antenna cable several times and always ensuring the threaded connections are straight and finger-tight. We notice that on some occasions the GPS may show some satellites in range, but when we disconnect the antenna, the next time we reconnect the cable, we encounter the same problem with no satellites being detected. The problem appears to be intermittent. This is a problem as we always disconnect and put the GPS in the storage case to avoid damage, and need to reconnect when we next use it.
  • We have allowed time for the GPS to “warm up” up to about one hour.
  • Testing the GPS out in the open with no overhead obstructions, e.g. in open parkland or empty car park.
  • Tested in metropolitan Sydney area where various satellites are usually picked up, e.g. inner west, city.

Any troubleshooting or testing we can pass along for this issue would be very helpful.

2

Try to use a different, known-good GPS antenna compatible with RTK systems.

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3

I’d first suspect an issue with the cable itself or the connection points…it may help to unscrew everything and go make sure the coaxial style connectors are all snug/flush/tight

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4

Are you comfortable with a DMM? I recommend measuring the voltage between the center pin and the outer shroud (don’t worry, you can’t damage anything).

image

When the unit is on, this should measure around 3.3V.

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5

Thanks for the assistance so far.

Regarding the connection points, we have tried unscrewing and reconnecting the connections ensuring these are snug/flush/tight, but this has had no impact on the issue.

3.3V was picked up with a multimeter from the centre pin and the outer shroud.

Do you have any other suggestions for things to check?

6

Since you sometimes get satellites, it sounds like an intermittent connection somewhere, possibly internal to your antenna or the Facet, or perhaps
you just have a couple bad cables.

Can you try another known working GNSS antenna?

Note that the SparkFun LoRa gear uses RPSMA cables while the SparkFun GNSS gear uses SMA connectors. This isn’t a knock on SparkFun, they follow industry norms. But you could attach a RPSMA connector (eg a cable for LoRa) to the GNSS receiver, have it fit seemingly perfectly, and not get a good connection…but maybe it might work a little bit. This probably isn’t the problem but just putting it out there.

SparkFun had an excellent info resource here:

https://www.sparkfun.com/pages/RF_Conn_Guide

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7

@CoreElectronics - Sorry for the delayed response! I lost this thread.

3.3V means the antenna is powered so that’s not your problem.

Next check is for a cold solder joint on the back of the SMA connector

image

Be sure the rear pin is soldered well to the PCB.

Assuming that’s all reasonable, then the next failure to check is for connectivity under the ZED which we’ll have to do here at SparkFun HQ. Please start an RMA and we’ll get the defective unit replaced as soon as we receive it.

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