Message from
Ivo at
Monday, 22-Jul-19 18:44:24 GMT@Kai,
First the easy part. The OperationCanceledException messages are just users disconnecting. Nothing to worry about.
The libusb_bulk_transfer failed message is something I still don't fully understand, but seems to be normal. This probably happens when the RTL-SDR drops some data, possibly because it was tuned in the middle of a data packet. Don't think this is something to worry about either as the software usually recovers from this just fine.
The RF Gain actually controls the tuner (chip) gain. Since the tuner chip is not used in direct sampling mode (below 28MHz), the RF gain won't do anything below that point, but should work above 28MHz.
Also I think 27 MHz is in the cross-over region at the top of what the direct sampling mode can handle and at the bottom of what the tuner chip can do, so I don't expect great reception there. Actually I just read on the rtl-sdr.com blog that "Frequencies between 14.4 and 28.8 MHz can also be received by using a band pass filter." - I am not entirely sure whether that would need to be done in software or hardware.
We have also had some problems with frequency offsets, which are far more problematic in the direct sampling mode with narrow filters. We have tried a few times to find the frequency offset by locating a radio station with a known frequency. Sometimes configuring this in the receiver settings helped to get things right.