osmocom-sdr February 2019

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gr-osmosdr: add clock_source= parameter
by Michael Loeffler 26 Mar '21

26 Mar '21

Hello, the attached patch allows to set the clock_source on uhd devices in programs like gqrx. Bye

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Bus error using rtl-sdr
by Amin Shah Gilani 13 Feb '19

13 Feb '19

Hi I'm experiencing a "bus error" everytime rtl-sdr tries to interact with my SDR. Here's a sample: rtl_fm -f 1000000 Found 1 device(s): 0: Realtek, RTL2838UHIDIR, SN: 00000001 Using device 0: Generic RTL2832U OEM Found Rafael Micro R820T tuner Tuner gain set to automatic. [R82XX] PLL not locked! Tuned to 1252000 Hz. Oversampling input by: 42x. Oversampling output by: 1x. Buffer size: 8.13ms Exact sample rate is: 1008000.009613 Hz Allocating 15 zero-copy buffers Bus error I'm running Kali on a Raspberry Pi, and I've used the repository version, and compiled from source — no change. The only thing that makes this error go away in `rtl_test` is to pass it the -S flag (forcing synchronous) flow. Does anyone have any idea how to fix this? If you'd like the Karma and would like to help solve this problem publicly for future users, Stack Overflow question continuously being updated is here: https://stackoverflow.com/questions/54657089/rtl-sdr-crashes-with-bus-error… ―Amin Shah Gilani <https://amin.gilani.me/>

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FL2K replace MT34TL/AS11D buck chip with LDO
by Ioannis Makris 08 Feb '19

08 Feb '19

I have managed to replace both buck DC-DC converters with AMS1117 3.3 & lm317 linear regulators and I successfully got rid of the mentioned 1 MHz buck converter clock to obtain as pure a signal as possible. Do not expect miracles as the DAC's are 8-bit and have a best case SNR of -48dB, but getting the sideband modulation out of the signal surely improves the resulting spectrum a lot. I have performed the mod on 4 fl2k adapters. Two of them came with a 1.2V AMS1117 for the 1.2V and a buck psu for the 3.3V. Another two came with 2 buck psu's Using 2 LM317 is a bit complex but can be done, as my proof of concept testbed has demostrated. One could actually fit them inside the plastic box. Mind you, linear regulators can get quite hot. Still not hot enough to inflict any damage after a 8-hour operation of the device. Another notable effect was the total elimination of "cb status 1" message on the testbed. The testbed suffered a lot of USB connection drops due to poor power delivery to the chip, which is also the plague of those devices that is causing bad reviews along with the poor assembly of the cable from those that use the device in regular vga output mode. The workaround is extremely simple; we use the onboard capacitors for filtering the output of the linear regulators, I install them inverted and add metal pins from 1/4W resistors to patch the power from the pin of the buck chip to the input of the linear regulator. Same with ground. Of course we are using USB3 interface that can provide more than 2.5W (500mA) of output power. I haven't thorougly tested device operation and stability under USB2.0 which has the aforementioned power limiting. The device looks stable though. There are implementations utilizing a pair of AMS1117 from factory. [image: 20190125_194224_001.jpg]

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FL2K replace MT34TL/AS11D buck chip with LDO
by matthew quirke 08 Feb '19

08 Feb '19

Has anyone tried replacing the MT34TL/AS11D buck converter/supply chip with a LDO regulator as Steve Markgraf suggested - my goal is to remove the harmonics, for HF tx. The MT34TL/AS11D(xx) datasheet is available online so it seems very do- able - just considering all the pitfalls - issues/ obvious things I missed ;) Any input/advice is much appreciated. -Matt

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osmocom-sdr February 2019