RTL-SDR V3 issues activating bias t

Have you got biast working at some stage and are looking for some switch development??

Before we get too much further can I point to my post above where I asked for rtl_biasT to be added into the piaware image.

I did eventually make rtl_biasT and I did manually test that I could turn the volts on and off. As I had gone down so many dead end paths attempting to follow the many instructions I found, I deleted that image and went back to a virgin image to ensure stability.

In answer to your questions then

  1. I have a Pi 3B

  2. I have a virginal piaware 3.5.3 in and running with the ONLY modification being Wi-Fi SSID and Password.

  3. Without breaking anything, I want to install rtl_biasT and turn it on before anything else claims the receiver.

My suggestion was for Flightaware to add the rtl_biasT functionality to the next image release and provide a method of turning it on in preferably the Configuation page in the My ADS-B page or in the piaware-config file.

I’d also be happy if someone could give a tested set of command to unambiguously setup a virgin piaware image to install the software and set a switch to turn it on first. (and yes, I like to use the words virgin and virginal in this context).

Thanks,

S.

ok. I have had biasT running. I have not developed any switching and have had to do every thing manually. What I have found, is that I need to be in exactly in the directory SRC. I make sure that I have turned off mutability BEFORE I switch on the bias t. Once I have confirmed the 4.5V output, then I re start mutability. So far, I have not had any issues apart from the obvious very manual way of getting this going before mutability is running. I take it you do not need any scripts etc to get bias t working, thats is what I could have provided :slight_smile: Jeff

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(1) This seems to be a low-priced solution.
The down side is very long delivery, Over 2 months.

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(2) This is another option, but at 5 times the price of (1).
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https://www.ebay.com/itm/Bias-Tee-Operates-from-10MHz-7000MHz-Bias-tee-Bias-T-DC-HDR-12V-or-USB-pwr/282542069310

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(3) Another option

https://www.ebay.com/itm/PCT-Series-PCTMPI1G-Power-Inserter-for-PCT-CM-Distribution-Amplifiers-or-Preamp/291540280382?hash=item43e127a43e:g:8HkAAMXQbcRQ5w3O

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(4) This is a DIY Bias-T, if anyone is interested in DIY.
Uses a recycled TV Splitter, a 200pF ceramic capacitor, and an axial inductor or self-made coil.

NOTE:
Click on the images in this post to see larger / full size

if your using systemd can you not set the biasT stuff up as a service (run once) and add it to the requirements of mutability service?

That way then mutability tries to start it has to start biasT first. Not 100% sure this will work but it might be worth looking at.

I bought a bias t via ebay last week, should be here on Tuesday I hope. https://www.ebay.com.au/itm/112742416931?ul_noapp=true

Thanks for those suggestions.

I checked one of my local suppliers and they have this.

http://www.radioparts.com.au/product/00760721/vc12pinj-‘f’-line-dc-power-injector-resi-linx

(87 in stock)

My buy price is only $AU2.20 so I will get a couple and crack one open and see how they do it and I can modify it if needed.

Thanks everyone for your suggestions.

S

@SweetPea11
Great find!
At AU$2.2, it is almost free. Good idea to buy a bunch and crack open one to see what is inside.

Whatever the physical configuration, in most bias-ts’, the circuit is basically a capacitor and an inductor, as shown in diagrams below:

Bias-T-Diagram-421x227px

Bias-T-microUSB-432x324px

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Please click here to see my post dated Sept 17, 2013. Its Photo #2 shows details of a DIY Bias-T which I have made at that time. There are notes added to the photo, explaining what is what.

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We can look into adding the option to piaware-config
OR
We can have the compiled command added to the piaware image. This would then require the user to enter one or two lines to set it up on boot.

The main problem is that liability is an issue. If someone turns on the bias-T and then shorts their RTL-SDR blog dongle or the dongle shorts something on the antenna feed then who is responsible?
I guess warning in multiple places can help a bit.

See the warning on the RTL-SDR blog dongle:
https://www.rtl-sdr.com/rtl-sdr-blog-v-3-dongles-user-guide/
This is a real problem that probably caused a few receivers to stop working.

Yes, please.

I’m NOT/NOT a lawyer, and this is NOT/NOT a legal opinion, but warnings, and making it ‘harder’ to activate accidentally, should take care of the issue.

Hi all. Agreeing with your believes David. Now my 2c worth. I have been fiddling with bias T and the rtl-sdr V3 dongle. Being powered from the dongle, I am not liking. I have already cooked one dongle, not even sure why and was very careful in what I have been doing with it. I realise that bias t is required for some amps that don;t also have an external power input,. The V3 dongle failure occurred on a unit indoors.

I do like the uptronics filter pre amp, an extra power input, as well as bias t, recommended in the FA build ADS-B reciever. Externally powered and a pretty good amp overall.

Having my PI3B+ up a mast, does present a small problem, where to get the external power for such an amp. With the POE hat, installed on the B+, it does have 2 x 5v outputs of the GPIO, which I have used to power this amp and so far, nil power issues with the B+, using this external 5v. I am waiting for a bias t injector, bought off ebay, which I plan to use with the rtl sdr’s ##RTL-SDR Blog ADS-B Triple Filtered LNA (Bias Tee Powered)##, using the power output of the POE hat. I used this amp, with the V3, on my indoor set ups, but want to try it on my B+ unit, up the pole. Unfortunately, it does not have an external power input and relies on bias t. This problem about powering up the bias t, via software, checking that power is actually being produce out of the V3 dongle and having it up a mast, would be a bit of a pain.

I want to compare the Uptronics amp and the rtlsdr blog amp, under performance and operational aspects, before choosing the final option for my POE ADS-B reciever, up the pole, theoretically and so far practically giving the best ADS-B performance of all (get rid of that coax run people…), in my set ups. More on that later, come on Ebay!!!

Morning David,

Thanks for considering this. I understand your dilemma.

Would an acceptable middle ground be

  1. The flightaware image has the compiled code included OR flightaware provides a command or commands to load and compile the software into an appropriate location. ( I am trying hard to NOT break the piaware image which I did attempting to follow the disparate instruction sets available ). A procedure such as the getting and installing the planefinder client with two cut and paste commands seems simple enough.

  2. Provide a simple and unambiguous instruction to set up so that, if required, the bias-T is switched on automatically each time the Pi is rebooted. I have had occasion to need to reboot one of my Piaware stations when I am not on the local LAN and have used the CONFIGURE popup on the Stats page. This process would need to reboot with bias-T without user intervention each time.

  3. Add whatever warnings you deem prudent.

That would be great.

Thanks,

S.

I have a suitable powersupply (5V) but I need to change the connector.

Looks well made.

Just need to sort out the extra cables and I’ll give it a blast.

S

It works.

I plugged the power supply in and the LED illuminated and there was 5V on the Type-F heading upstream.

The amplifier seems to be getting power and doing what amplifiers are supposed to do.

I still need a simple and reliable way to turn on bias-T volts in the V3 dongle so I don’t need this anymore as this introduces a few losses and compromises.

It will introduce some loss just by being in circuit and it introduces a couple of Type-F connectors that I would not need.

It also requires power to inject and my current design has the V3 dongle up the mast with a 5M USB cable down to the Pi. This injector would require a separate 5V supply run up the tower whereas if the V3 did the injection the power will come from the USB to the V3 (hopefully!!!) Still to be tested but the V3 runs quite happily at the end of the 5M USB cable.

I’ll sort something out in the meantime.

S.

For those who use Flightradar24’s Pi24 image, and want to use RTL-SDR V3 with Bias-T Enabled:
The Pi24 image has dump1090-mutability pre-installed. The peculiar thing with this image is that dump1090-mutability does NOT start by default at boot. When FR24 feeder starts, it gives command to dump1090-mutability v1.14 to start. This means the package rtl_biast should be started before fr24feed starts. This can be done by modifying fr24feed.service file to start rtl_biast before fr24feed. For details see posts linked below.

In case of Piaware image or Raspbian image, similar action may be possible with dump1090-fa.service or dump1090-mutability.service files.

Post #5

Post #6

Post #7

@obj
I think i found the root cause for the problems for the guy posting in the original post.
(someone else had a similar problem)
There is insufficient blacklisting of some kernel drivers.

Why did you remove this file going from debian-wheezy to debian?

debian-wheezy/dump1090-fa.modprobe
# This system has dump1090-fa installed, which wants to use RTL2832-based
# digital video dongles in SDR mode via librtlsdr. This file prevents the kernel
# video4linux drivers from loading.
blacklist dvb_usb_rtl28xxu
blacklist rtl2832

Could you add that blacklisting back to dump1090-fa?
Or is it no longer required?
(I’ve also blacklisted rtl8192cu and rtl8xxxu but those are blacklisted on the piaware sd-card as well via files in /etc/modprobe.d and i’m not sure where those files even come from)

Anyway updating the guide at this address:
https://www.rtl-sdr.com/getting-the-v3-bias-tee-to-activate-on-piaware-ads-b-images/

Including the udev rules it supports would also work i guess.
@abcd567
You have some posts in various places in regards to this.

Maybe just expand the cmake line like described there
RTL-SDR V3 issues activating bias t - #13 by jlb56

so the block of code reads:

cd ~
git clone https://github.com/rtlsdrblog/rtl_biast
cd rtl_biast
mkdir build
cd build
cmake .. -DINSTALL_UDEV_RULES=ON -DDETACH_KERNEL_DRIVER=ON
make

(I’m pretty sure only the detach kernel driver part is required but the other part about the udev rules doesn’t hurt.)

Something to check. I have both RTL-SDR Blog’s v2 and v3 dongles. v2 had a hardware provision for bias-T. It was just a short between 2 pads on the circuit board. v3 added software switching of bias-T.

Maybe, as I have not checked it, the 2 pads are also present on the v3 dongle circuit board. Search for the v2 dongle on the RTL-SDR Blog, to see a picture of the circuit board, and compare it to the v3 circuit board.

Whoever adopts this solution must keep in mind that voltage will be present all the time. Careful what you connect to it, if other than a bias-T capable LNA.

Thanks @wiedehopf for the suggestion.

I have posted the code to make rtl_biast in following two posts in Flightaware forum, but unable to edit these as editing of old posts is blocked.

(1) Dump1090-mutability v1.15~dev and RTL-SDR V3 Bias-T Auto Switch-ON

(2) RTL-SDR V3. Experiment to Enable Bias-T

However I can edit my posts in Flightradar24 forum for enabling bias-t on (1) Pi24 image and (2) Raspbian img with dump1090-mutability v1.15~dev.

I will edit both these FR24 posts shortly.

Because that stuff is managed by the debian-provided rtlsdr packages on jessie and newer. wheezy is only special because there’s no prepackaged librtlsdr available.

I see.

Still it was convenient for me to blacklist two additional drivers on Raspbian Stretch Lite.

I guess if detaching the kernel driver is handled properly there is no real need for blacklisting.
And just that is done by -DDETACH_KERNEL_DRIVER=ON i suppose.

Thank you for explaining :slight_smile:

Still curious why librtlsdr would blacklist two drivers, but not others.
Or do these two files belong to another package?

/etc/modprobe.d/blacklist-rtl8192cu.conf
/etc/modprobe.d/blacklist-rtl8xxxu.conf