PLL not locking: DOA dongle?

General
1

I’m new to RTL-SDR, but not to phase locked loops. I’m getting the same error across both a Windows 11 PC and a MacBook, both with full updates and the latest drivers for my v3 RTL-SDR blog dongle:

[R82XX] PLL not locked!

I have tried different center frequencies from hundreds of kHz to hundreds of MHz (target is 915 MHz), and cannot get a PLL lock. I am starting to worry that this dongle is DOA and I am going to waste a lot of time trying to troubleshoot a broken device.

Can someone weigh in? I am giving it 24 hours and back to Amazon it goes otherwise.

Edit: Example output, while I am sitting 1m underneath a weather station broadcasting at 915Mhz with freq hops:

rtl_433 -Y classic -s 250k -f 915M
rtl_433 version 25.12 (2025-12-12) inputs file rtl_tcp RTL-SDR with TLS

New defaults active, use “-Y classic -s 250k” if you need the old defaults

Found Rafael Micro R820T tuner
[SDR] Using device 0: Realtek, RTL2838UHIDIR, SN: 00000001, “Generic RTL2832U OEM”
Exact sample rate is: 1000000.026491 Hz
[R82XX] PLL not locked!

time : 2026-05-16 17:53:16
model : SCMplus id : 75354654
Protocol_ID: 0x1E Endpoint_Type: 0xAB Endpoint_ID: 75354654 Consumption: 38687 Tamper : 0x4900 crc : 0x0EBD
Meter_Type: Water Integrity : CRC
x _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
time : 2026-05-16 17:55:35
model : SCMplus id : 75420629
Protocol_ID: 0x1E Endpoint_Type: 0xAB Endpoint_ID: 75420629 Consumption: 40947 Tamper : 0x4900 crc : 0x0983
Meter_Type: Water Integrity : CRC

time : 2026-05-16 17:57:41
model : SCMplus id : 75356411
Protocol_ID: 0x1E Endpoint_Type: 0xAB Endpoint_ID: 75356411 Consumption: 34816 Tamper : 0x4900 crc : 0x5E9E
Meter_Type: Water Integrity : CRC

Looks like it sees my neighbors’ water meters, but not the weather station. And PLL is still not working. Any help would be greatly appreciated!

2

Hi, it’s important to note that PLL not locked is not an error to worry about. This warning will always be shown and it doesn’t mean there is a defect.

Basically the dongle can initially take a few tries to lock the PLL which is jusy how it works.

As long as this message isn’t constantly scrolling, the warning is meaningless. If it’s not constantly scrolling the PLL has successfully locked.

3

Thank you! That explains why I am able to see the water meters. Next question: Why can’t I see any signal from the Davis? I am guessing I am tuned to the wrong frequency, it is frequency hopping, and/or the bandwidth around center frequency doesn’t encompass where the Davis happens to be. Not sure of how fast it hops around. I have a 915 MHz antenna heading my way just to make SNR a less likely issue.

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4

I am now able to hear the Davis: key was switching to rtldavis from rtl_433. The former is able to handle the frequency hopping. Many thanks to rtlsdrblog, I am much closer to my ultimate goal!

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5

I was successful in getting this all to work. I’ve created a github repo and a docker image. Posting links here, will work on optimizing these and adding functionality, but they were generated with a lot of Claude.ai, for transparency.

I was able to use this dongle to communicate with my Davis ISS on my MacBook, and now my NAS, where I run a dockerized weewx and utilize rtldavis. Couldn’t get it working on my PC: got a lot of errors regarding finding the frequency and following the hops (902 to 928 MHz), something about how USB in Windows makes that hard to do properly. Not sure what it all meant, but it wasn’t a requirement for me since the NAS was my end goal (and where the dongle is plugged into).

https://github.com/WeatheredScientist/weewx-rtldavis/
https://hub.docker.com/repository/docker/weatheredscientist/weewx-rtldavis

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