RTL-SDR loses data when decode first starts...

hruskacha

Member
Premium Subscriber
Joined
Nov 9, 2020
Messages
277
Location
Muskegon
When using SDRTrunk, All of my P25 transmissions get sync loss for the first frame or two across all TGIDs and Sites. I use 4x rtl-sdr V3's and they all have the same symptom, initial decode gives bad data. I did A test with rtl_test and I got data loss at the very beginning of the test, just like sdrtrunk... It does this for all six of my RTL-SDR V3's, on 3 different PCs, and both on Windows 10, 11, and Linux. I switched USB ports and hub configurations.

Is this a tuner issue? USB Bus issue? It only loses the first few samples when decode first starts. The test ran for awhile without any issues...

1720196821136.png
 

hruskacha

Member
Premium Subscriber
Joined
Nov 9, 2020
Messages
277
Location
Muskegon

From Amazon, but that brand
 

dave3825

* * * * * * * * * * * *
Premium Subscriber
Joined
Feb 17, 2003
Messages
8,197
Location
Suffolk County NY
And they were all sold by Rtl Sdr Blog?


1720531501676.png




I got data loss at the very beginning of the test, just like sdrtrunk... It does this for all six of my RTL-SDR V3's, on 3 different PCs, and both on Windows 10, 11, and Linux. I switched USB ports and hub configurations.

Did you buy them all at the same time or at different times? Would think if it's the same on different PC's running different operating systems and different usb hubs that it would pretty much rule out usb, cpu or usb issues and could possibly point to a bad batch. Did you run a test with or without the usb hubs?
 

hruskacha

Member
Premium Subscriber
Joined
Nov 9, 2020
Messages
277
Location
Muskegon
They were sold by rtlsdr blog on Amazon. And I tried both front and back USB ports, 2.0 and 3.0
 

hruskacha

Member
Premium Subscriber
Joined
Nov 9, 2020
Messages
277
Location
Muskegon
And they were all sold by Rtl Sdr Blog?


View attachment 165407






Did you buy them all at the same time or at different times? Would think if it's the same on different PC's running different operating systems and different usb hubs that it would pretty much rule out usb, cpu or usb issues and could possibly point to a bad batch. Did you run a test with or without the usb hubs?
And by hub I meant the integrated hub on the PC, 4x front, 6x rear.
 

hruskacha

Member
Premium Subscriber
Joined
Nov 9, 2020
Messages
277
Location
Muskegon
Well, here are some important things to consider...

1. They have been running nonstop since July 2021 (like a CHAMP!!! until recently)
2. The 3 PCs are two identical Dell Optiplex 8010's, and a smaller optiplex. So hardware is near identical, but I have new SSDs in them.

Maybe time for a new batch of SDRs?
 

rabbit108

Member
Joined
Jan 4, 2021
Messages
362
Location
S.E. VA
Well, here are some important things to consider...

1. They have been running nonstop since July 2021 (like a CHAMP!!! until recently)
2. The 3 PCs are two identical Dell Optiplex 8010's, and a smaller optiplex. So hardware is near identical, but I have new SSDs in them.

Maybe time for a new batch of SDRs?
My guess:
Sounds like a USB write-speed problem to the new SSDs.

What happens if you try a powered hub with one or two SDRs?
 

hruskacha

Member
Premium Subscriber
Joined
Nov 9, 2020
Messages
277
Location
Muskegon
So I tried rtl_test with a lower sample rate of 1920000 Hz and the decode issue is now resolved. I guess its a USB memory buffer issue?
 
Top