RTL-SDR v3 bias tee power on/off - 3 methods for 3 different installs

[abcd567]

(1) Method for dump1090-fa

Originally in 2017 Oliver Jowett (@obj) has proposed a method to turn on bias-t by adding a command in dump1090-fa.service file.

https://discussions.flightaware.com/t/enable-biast-on-rtl-sdr-v3-before-dump-fa-piaware-start/20046/2

Subsequently in mid 2018 (1) Akos and (2) RTL-SDR Blog posted this method on their web pages. Both sites have “Credits” at bottom of their pages, and have given link to @obj’s method.

http://www.radioforeveryone.com/p/piaware-with-rtl-sdr-blog-v3-and-ads-b.html

https://www.rtl-sdr.com/getting-the-v3-bias-tee-to-activate-on-piaware-ads-b-images/

(1) Method for dump1090-mutability ver 1.15~dev

The method posted on the RTL-SDR Blog is applicable to dump1090-fa only.
It does not apply to dump1090-mutability v1.15~dev, as the dump1090-mutability service files ( dump1090-mutability.service ) are automatically generated by systemd-sysv-generator , and all the changes made by user are overwritten at restart / reboot.

However as the systemd-sysv-generator generates dump1090-mutability.service by reading from file `/etc/init.d/dump1090-mutability, in mid 2018 I have added bias-t start and logging script in the init file, and it works OK. Detailed steps are given here:

RTL-SDR V3 Dongle
Enabling Auto Switch-ON of Bias-T in dump1090-mutability v1.15~dev.

(3) Method for Flightradar24’s Pi24 image

In the Pi24 image, the default startup of it’s dump1090-mutability ver 1.14 at boot is blocked by FR24 programmers . It is configured to be started by fr24feed, with all the necessary config parameters supplied by fr24feed, and NOT by init file of dump1090-mut.

Due to above, in mid 2018 I have proposed to add bias-t startup command in fr24feed’s service file (i.e in file fr24feed.service). Detailed steps are given here:

RTl_SDR v3 bias tee power on/off Raspberry pi

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[Obadiah3244]

abcd567,

Thanks for the post.

I needed a refresher on how to do this.

In the mean time, I’ve had good luck with this:

https://www.ebay.com/itm/Bias-Tee-Operates-from-10MHz-7000MHz-Bias-tee-Bias-T-DC-HDR-12V-or-USB-pwr/283337131917?_trksid=p2485497.m4902.l9144

[theresjam]

https://www.rtl-sdr.com/in-testing-customized-drivers-for-rtl-sdr-blog-v3-sdrs/

this could make life a bit easier

[abcd567]

SOURCE: https://www.rtl-sdr.com/in-testing-customized-drivers-for-rtl-sdr-blog-v3-sdrs/

NOVEMBER 1, 2019

IN TESTING: CUSTOMIZED DRIVERS FOR RTL-SDR BLOG V3 SDRS

We’ve recently released a modified version of the Osmocom RTL-SDR drivers that has a few enhancements particularly for RTL-SDR Blog V3 units. The changes merge improvements to L-Band PLL locking performance which may be necessary for operating units in high ambient heat environments and the RTL_TCP performance enhancements by Stephen Blinick.

If you want to toggle the bias tee ON/OFF in SDR#, we’ve also made use of the “Offset Tuning” checkbox in the RTL-SDR settings. This checkbox is unused for R820T2 RTL-SDRs, so we’ve added code that will toggle the bias tee ON/OFF with this checkbox.

In addition we’ve also made use of some unused EEPROM flags to create a method that allows you to force the bias tee to be always ON if a certain EEPROM flag is set. You can also force direct sampling mode with another EEPROM flag. Note that these force flags will only work if you are using these drivers.

A Windows release is available on the Github Releases. To use with SDR#, simply replace the rtlsdr.dll file in the SDR# folder with the one in the Release.zip file. To install on Linux, follow the instructions in the Readme, and remember to follow the instructions to remove librtlsdr-dev if you previously installed drivers via the package manager.

If there are any problems or feedback, please open an issue on GitHub. List of changes shown below.

1. VCO PLL current fix - Improves stability at frequencies above ~1.5 GHz Beta testing a modified RTL-SDR Driver for L-band heat issues

2. RTL_TCP ring buffer enhancement by Stephen Blinick Significantly Improving RTL_TCP’s Performance with Ring Buffers

3. Enabled direct sampling for rtl_tcp

4. rtl_biast program added, including the ability to turn on/off any GPIO

5. Hack to force the bias tee to always be on by setting the unused IR endpoint bit to 0 in the EEPROM. Example to force the BT to be always ON “rtl_eeprom -b y”, to remove forced BT “rtl_eeprom -b n”

6. Hack to force direct sampling to be always on by setting the unused remote-enabled bit to 1 in the EEPROM. Example to force direct samping always “rtl_eeprom -q y”. To remove forced direct sampling “rtl_eeprom -q n”

7. Repurposed “offset tuning” to toggle bias tee ON/OFF. We can now use the “offset tuning” button in SDR# and other programs to toggle the bias tee if there is no specific button in the GUI.

[heliosh]

It would be nice if the bias-T could be enabled just by having a variable in the dump1090-fa config file, without running external programs.
It should be possible, since it is supported by the rtlsdr-lib.