Over on her YouTube channel SignalsEverywhere, Sarah has uploaded a new video showing how to use a program called 'hacktv-gui' to transmit analog TV signals using a HackRF software defined radio. Analog TV standards such as PAL and NTSC have been phased out in most of the world in favor of digital TV standards instead. However, transmitting these yourself can be a fun experiment that may help breathe life into old television sets.
In the video Sarah explains how to use the hacktv-gui and hacktv software, and how to create a video transmission. She mentions how hacktv also supports the use of a FL2K device, which is a cheap VGA adapter that can be used to transmit signals.
HackTV | Analog Television Transmission with a HackRF SDR
The FL2K project allows us to turn a cheap USB 3.0 dongle into a fully transmit capable SDR (filters still required for high power work). We have posted about the FL2k project several times on this blog since early 2018.
Recently we thank reader Mikael for submitting a fork of the Osmo-FL2K driver code which he writes enables it to generate white noise with uniform amplitude distribution. This could be useful for projects that require a wideband noise source such as when attempting to measure filter and VSWR of antennas.
IK1XPV, author of the code notes that the current code is only tested on the Windows driver branch, via compilation on Visual Studio 2019 at the moment. The main contributed code can be found in \src\fl2k_noise.c.
An FL2k Dongle connected to an RTL-SDR via VGA to BNC Breakout Cable and Attenuators
[mrgriscomredux] over on [Reddit] was interested in re-creating the nostalgia that was scrambled analog television from the 90s. To do this he captured an NTSC analog video signal using an RSP1 SDR and demodulated that into composite video using GNU Radio to process everything.
The methods that were originally used to scramble analog television are not well documented, however [mrgriscomredux] has done a fine job re-creating it himself in his own way.
He then uses a Python script to modify the “Gated Sync Suppression” within GNU Radio and then transmits that back on to the air using a low cost FL2K VGA adapter we’ve featured on the blog in the past.
These FL2K VGA adapters can be abused as crude software-defined transmitters and we’ve seen people do everything from video transmission to GPS spoofing with them. [Check out the FL2K article here]
Osmo-FL2K can be considered as the [evil] transmit-side brother of RTL-SDRs. It is a driver that allows cheap $5 - $15 USB 3.0 VGA adapters to be used as a transmit-only capable SDR. It might be considered [evil] as transmitting illegally and without filtering can pollute the RF spectrum, but being responsible with it and using appropriate filters could enable extremely low cost transmitters.
Recently at the October 2018 Osmocom Conference, Steve M, the man behind the Osmo-FL2K discovery and software (and heavily responsible for the development of RTL-SDR too) has given a talk titled "osmo-fl2k - the [evil] transmit-side brother of RTL-SDR". In the past he's also given a similar talk that we posted about previously.
The talk goes over the discovery and reverse engineering of Osmo-FL2k, discussion of the application itself, some signals that have been successfully transmitted and some measurements.
Osmocom is behind the discoveries of RTL-SDR and OsmoFL2K. If you'd like to support them please donate at OpenCollective, and check out their other projects at osmocom.org.
osmo-fl2k - the [evil] transmit-side brother of RTL-SDR
Thank you to Sajjad Golchin Poor for writing in and letting us know about his success with getting Osmo-FL2K to run in WMWare Workstation Pro. Osmo-FL2K is a driver that enables very cheap VGA dongles to work as a SDR transmitter. Previously in our initial first tests with the FL2K-SDR we discovered that it wouldn't connect to a Virtual Box virtual machine, but theorized that it might work in the commercial (non-free) version of VMWare as that has known working USB3.0 support. Regarding his tests in VMWare, Sajjad writes:
...I started working with Virtualbox but as you said the USB 3.0 drivers have some problems and cannot disconnect dongle from the host and attach back to the guest.
So I went for VMWare Workstation Pro 14 and after booting the GNU radio live image and attaching the dongle and installing the drivers it worked perfectly at transmitting WBFM on the virtual machine. For permanent use of dongle I downloaded and installed Ubuntu 16.04 latest version and it is working flawlessly right now on the VMWare.
Something that I realized during my test was that the maximum achievable sample rate in VMWare environment is a little bit lower (by Max. 10Ms/s) than what was expected but I guess it is ok for most applications. (it may be because of VMWare USB 3.0 drivers.)
Another thing that I came up with was that some sample buffers may drop during the delivering process to FL2K and it can ruin the whole transmission process. for example, when I was transmitting WBFM after a few minutes it stopped transmitting without any warning/error in the console and the machine thought that it is delivering the samples right to the device. It happened to me both in the VMWare environment and GNU radio live bootable so it might be a software issue.
Sajjad also that he's able to achieve sample rates of at least 145 MS/s in VMWare, but that maximum rate that it locks at always seems to vary between 145 - 157 MS/s
We have been wondering if anyone else has been successful in getting an FL2K dongle to run smoothly in a virtual environment? If you have please post in the comments.
Examples of compatible Osmo-FL2K USB to VGA Adapters.
If you've recently purchased an FL2K-SDR to use as a cheap osmo-fl2k transmitter and found that it only works on USB 2.0 ports, or at very slow sample rates, then you may have received a defective unit. Over on his blog Yohanes Nugroho discovered that his FL2K-SDR was experiencing these issues. Upon opening it up he discovered that the wiring inside looked different when compared to the sample image found on the Osmo-FL2K website.
Looking further into it he found that the USB wiring was soldered on incorrectly. After resoldering the wiring Yohanes was able to get the FL2K-SDR working properly at high sample rates on USB 3.0 ports.
Over on Hackaday.io Ted Yapo has written about his frequency marker generator which uses Osmo-FL2K. Osmo-FL2K is a recently released hack that allows cheap $5 - $15 USB 3.0 to VGA adapters to be used as an SDR transmitter. We have several posts on it available here. The FL2K-SDR frequency marker generator tool simply generates an AM voice that reads out the current frequency on all of the 118 US AM channels. He writes:
A frequency marker generator is a very useful tool for calibrating antique or experimental (even crystal!) medium wave (aka AM broadcast band) radios. While an RF marker can be as simple as a fixed frequency oscillator, that's not the most convenient way to calibrate multiple frequencies. This project provides a software-defined-radio solution for a deluxe marker generator using a cheap USB-to-VGA dongle. The output signal consists of 118 individual AM "stations" in the MW band - one for each assigned channel in the US - each announcing their own frequency in a synthesized voice.
In the future Ted hopes to be able to generate a full band of old radio shows that could be sent to an antique radio, which is sure to help in improving that authentic antique feeling.
If you're interested in Osmo-FL2K his hackaday.io page also has information on throughputs that he got from different USB interfaces on his PC, as well as a PCB breakout board to convert the FL2K-SDR VGA port into SMA outputs.
Recently we've been posting about the release of Osmo-FL2K which is a software hack that allows cheap $5-$15 USB 3.0 to VGA adapters to be used as a transmit-only capable SDR. It is an excellent compliment to the RTL-SDR.
Osmo-FL2K was created by Steve Markgraf of Osmocom who gave a presentation on it at this years OsmoDevCon conference. The video was released today and in it he explains the history of VGA transmitter hacks, explains how Osmo-FL2K works and finally discusses some results.
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