DATV-Express Tx Board Overview


DATV-Express boards are not available. We decided not to make another production run. If you still want a board, send a message  to the DATV-Express forum and we will put your name on the list of  those wanting boards. If enough people want boards, we may consider making another production run. Thank you.”

It had been a long, slow 3 year process developing a quality state-of-the-art digital ATV transmitter board. The DATV-Express project team announced on 2014-02-01 that the software was now ready for production release and the boards could be ordered via PayPal on the PURCHASE page of this web site. (Please note that you need to be logged in to this web site in order to see the PURCHASE page.)  

The initial world-wide sales of DATV-Express boards have gone well…and rather smoothly. Art WA8RMC has now received a second batch of production boards at the end of December (2014). 

2016-11-01 blog below

DATV-Express v1.23 software now can run on Windows Operating System (32-bit or 64-bit OS). Charles G4GUO was able to correct the last reported problem for DVB-S2 protocol and has released v1.23 software for Windows. Also, an experimental set of coding for DVB-T protocol (2 MHz and 1 MHz channel-bandwidths only) was included in that Windows software release.

v1.23 on Windows OS
Block Diagram for v1.23 using WINDOWS OS with DATV-Express set-up for DVB-S protocol. The DVB-S encoding occurs inside the FPGA.
v1.23 on WinOS for DVB-S2
Block Diagram for v1.23 running DVB-S2 protocol. Both the CODECs and the DVB-S2 protocol encoding are run on the Windows PC because the FPGA is not large enough.

2015-01-01 blog below

Charles G4GUO has been working on adding a new mode to the DATV-Express software, a Reduced-Bandwidth DVB-S Digital-ATV (RB-DATV) signal for the new 146 MHz band in UK. The goal is to start up some DATV activity on the UK’s newly opened 146 MHz band using very low Symbol Rates around 0.300 MSymb/sec to 0.333 MSymb/sec to produce a small DATV bandwidth around 0.5 MHz centered on 146.5 MHz

Narrow-BW DVB-S signal
Narrow-BW DVB-S signal produced by DATV-Express exciter board on 146.5 MHz with SR = 333 KSymb/s. The frequency span on the Spectrum Analyzer is 1 MHz wide.

The DATV-Express software is being experimentally modified to produce a clean signal spectrum with NO alias images being produced when using very low SR. This is not as easy as it sounds….but, by using SDR and some FPGA coding changes, Charles was able to add x64 frequency interpolators coding simply to get the aliases to go to frequencies outside of the 5 MHz analogue Nyquist filters cutoff (for example 0.2 MSymb/s SR x64 = 12.8 MHz and alias filtering is achieved). The current plans are to use DVB-S with H.264 video compression to produce a video frame rate that is as fast as possible. G4GUO first tried to use a Mitsubishi 2M RF amplifier brick RA06H1317M (I believe rated at 60W FM at 150 MHz) and obtained terrible spectrum-distortion results. Charles could only obtain 750 mW average power output before excessive spectrum-distortion set in. Charles is now exploring the use of a “RF amplifier distortion correction” approach (sometimes called “pre-distortion” or “pure signal”) to reduce the spectrum distortion. I hope the reader will realize that these “narrow-bandwidth” techniques are not just restricted to 146 MHz and could also be used on any crowded DATV band in any country to insert a narrow 0.5 MHz BW DATV signal into a crowded band-plan spectrum.

Ken W6HHC has started to investigate software changes needed to use the Logitech C920 web cameras to produce H.264 directly for the DATV-Express board and eliminate the need for Hauppauge video-capture units. Not an easy task…looks like Ken will need to do some software coding and learn how to compile in a linux world. Fortunately, Alex OZ9AEC has been working with the C920 web camera on a Raspberry PI and has supplied plenty of direction and suggestions.

Art WA8RMC has received a new production batch of new DATV-Express hardware boards just before Christmas. So there is no shortage of boards that can be ordered directly from this web site on the “PURCHASE A BOARD” page (you must be logged into this web site to make the purchase.. Here is a report on where boards have shipped in 2014:       

  • Australia 9%)
  • Belgium 3%
  • Brazil 1%
  • Chile 1%
  • Denmark 1%
  • France 2%
  • Germany 6%)
  • Italy 1%
  • Japan 7%)
  • Netherlands 4%
  • Switzerland 4%
  • UK 31%
  • USA 28%

2014-12-01 blog below

Good news! DATV-Express software to run on the ODROID has been released!– Since March, Charles G4GUO had been working to port the DATV-Express software to a smaller and more-portable ARM-based “micro-PC”. The project team tried using:            

  • Raspberry Pi (single-core ARM)
  • RikoMagic MK802iv (quad-core ARM)
  • HardKernel ODROID U3 (quad-core ARM)

The Raspberry Pi and the MK802iv units were tested with the DATV-Express hardware  board and software…but, each had problems when tried with our project. The single-core-ARM Raspberry Pi, running at 700 MHz, was underpowered for our particular use. The MK802iv had issues with the completeness of its software repositories…that prevented easily recompiling the linux kernel software. The small ODROID model U3 (see Fig O-1 below), quad-core-ARM CPU running at 1.7 GHz, was tested and proven to be suitable for meeting our DVB-S goals.

Size Comparison of ODROID model U3
Figure O-1 – Size of quadcore-ARM ODROID-U3 board is about the same size as Raspberry Pi

Fig O-2 below, illustrates a typical transmitter set-up block diagram for using the ODROID U3 to drive the DATV-Express board in a typical DVB-S operation. This approach uses a USB2-based Hauppauge model HVR-1900 (PAL) or the HVR-1950 (NTSC) to perform video capture.

Block Diagram using ODROID U3
Figure O-2 – Typical Block Diagram of ODROID DVB-S transmitter using DATV-Express

Ken W6HHC spent six weeks taking G4GUO’s code from his github to build the .deb distribution package using debreate (a tool)…then testing…then documenting. The DATV-Express v2.03 software for ODROID model U3 performs all the functions using the Lubuntu 14.04 LTS operating system as the larger PC with Ubuntu OS, except the DVB-T performance is more limited. One of the first tests run on the ODROID U3 was to try the new 1 MHz channel bandwidth mode for DVB-T that was added in the v2.03 release of software. 1 MHz bandwidth works well. DVB-T with QPSK in the 2 MHz BW mode was also tested. But, project testing proved that one of the four ODROID CPU cores was NOT able to keep up with the required processing load for the 2 MHz BW testing. Charles G4GUO suspects that further DVB-T load-reduction improvements could possibly be done by rewriting parts of the software in assembly language (but, that assy code effort will not occur soon).

Tutioune analyzer receiving DVB-S
Figure-O3 – Tutioune analyzer receiving DVB-S “Test Pattern” transmission while using ODROID

Updated README details, a new .DEB download file for ARMhf, and a separate User Guide for ODROID (Draft04) are now all available on the DOWNLOADS page on this DATV-Express web site.

Ken W6HHC also wrote an article called “Digital-ATV – Using ODROID with DATV-Express board”. This article can be found as DATVtalk12 in the free eMagazine called CQ-DATV18 that can be downloaded at:   http://www.cq-datv.mobi/ebooks.php
The article can also be found as TechTalk116 on this web site on the left side of the Home Page using the link called TECH TALK ARTICLES. 

2014-10-12 blog below

The DATV-Express project team (with a little help from hams around the world  testing a draft build) have “Production Released” v2.03 software for PCs uaing 32-bit or 64-bit Ubuntu OS.

The new DATV-Express software has the following new changes:

  • V2.02 had timing problems with old STB receivers with small buffers, where the DATV-Express PCR timing-processing overflows the buffer (after a several minutes) resulting in video screen freezes or screen going blank…and/or audio popping.
  • In V2.02 there was still a lingering problem with some older models of PCR-150 units where DATV-Express could not properly grab the composite video.
  • V2.03 can now be installed on Ubuntu V14.04 LTS (as well as older the older Ubuntu V12.04 LTS)
  • V2 .03 adds a new feature of a DVB-T  1 MHz bandwidth selection. 

The README  details, new .DEB download files, and User Guide (Draft36) are all available on the DOWNLOADS page of this web site.

2014-04-30 blog below

First, the BAD News– In April, Charles G4GUO managed to get the Raspberry-PI software working as shown in the “Raspberry-Pi Development-phase03” block diagram in the March blog below.  He was able to get it work up to 8 MSymb/sec….BUT it would only run for a few seconds before the software froze. There were two major obstacles. First, the way Raspberry-PI handles USB traffic is to do a “lot of writing to memory” and this consumed CPU-cycles. The CPU consumption on RPI was running maybe 40-80% depending on the Symbol-Rate used. Second, any GUI movement would spike the CPU-cycles to 100% and everything stopped. Charles’ conclusion was the Raspberry-Pi single-core-ARM processor running at 800 MHz does not have enough CPU-horsepower for our project!

Now, the GOOD News – Charles tried using an RKM MK802iv “mini-PC” that is sold on Amazon for turning television sets without internet access into “smart TV’s” that could surf the internet and watch movies via Netflix download or streaming video, etc. See FigA1 below for a size comparison of this “mini-PC’ unit from RikoMagic (RKM).

Size Comparison of MK802iv
Figure A1 – Size comparison of quadcore-ARM MK802iv with a deck of cards. 
Block Diagram of typical MK802iv set-up
Figure A2 – A Block Diagram of typical MK802iv set-up for transmitting DVB-S. 

Charles was able to push the MK802iv unit to drive the DATV-Express board at 12 MSymb/sec with DVB-S protocol. A block diagram of the MK802iv DVB-S test set-up is shown in FigA2. The block diagram components shown in dashed-lines (Display, keyboard, etc.) are only needed to set-up and configure the software. The dashed-line components are not actually needed to run the transmitter….just a real SPST switch to act as PTT.

Ken W6HHC spent about a week “polishing” the rough-edges for installing the DATV-Express software on the MK802iv. Ken explains that the MK802iv can be purchased in two flavors. One flavor comes running Android “Jelly Beans” OS. The second flavor comes running Linux OS (called the LE edition). In both cases, the user needs to re-flash-the MK802iv unit to put a different Operating System called PicUntu v4.5 (a light-weight variety of ubuntu linux) onto the unit. All of the software flashing tools and PicUntu v4.5 are free to download on the internet…and takes maybe 15 minutes perform the re-flashing step.

The plans for the team now are for Charles G4GUO to continue testing and refining the DATV-Express software for the MK802iv, Ken W6HHC will begin drafting a “standalone” User Guide version to support future MK802iv users, and Art WA8RMC will be demonstrating DATV-Express at the Dayton HamConvention in May.

2014-03-31 blog below  

Charles G4GUO has been now working full-time on allowing the Raspberry-Pi processor to drive the DATV-Express board in DVB-S protocol (instead of using a full-blown Ubuntu PC). This is not a quick project and we see at least four “development phases” to finishing our  Raspberry-Pi work.

Development-Phase01 –  move all DVB-S encoding into FPGA and talk to board with ubuntu-PC using MPEG-2

Development-Phase02 – integrate ubuntu code used in phase01 into Raspberry and use MPEG-4 payload with PI-camera and a DVB-S2 STB (see Fig01)

Development-Phase03 – use Hauppauge USB encoder to produce true MPEG-2 with the DVB-S protocol

Development-Phase04 –  combine DVB-S dongle receiver with Phase03 to create a DVB-S transceiver that is Raspberry-Pi controlled

Raspberry-Pi effort for Phase02
Figure 1 – Block diagram of an interim-development phase for Raspberry-Pi effort (called “Development-Phase02”) using MPEG-4 payload from a PI-camera with DVB-S protocol.  NOTE – a DVB-S2 STB is used to get access to MPEG-4 decoding CODECs 
Raspberry-Pi effort for Phase03
Figure 2 – Block diagram of “Development-phase03” for Raspberry-Pi using Hauppauge encoder to produce genuine DVB-S NOTE – Keyboard, mouse, hub, and display (in dashed lines) only needed to configure the transmitter. 

Charles has now completed “Development-Phase01” by moving all DVB-S encoding into the FPGA on the DATV-Express board and testing it with an ubuntu PC. Now G4GUO is in the middle of working on Raspberry “Development-Phase02”. Charles G4GUO points out that there can be many ways to configure a Raspberry-Pi with the DATV-Express board, including using Ethernet or Wi-Fi to configure settings for transmitting.

2014-02-28 blog below

Charles G4GUO also made a number of tweaks and clean-up of little bugs in releasing v2.01 of the software during February. The v2.01 software is available on the DATV-Express.com web site under the DOWNLOADs link. Details of the actual changes are described in the README document, also located on the DOWNLOADs page. However, one new feature of the v2.01 software was to automatically invoke the “x2 iFFT math” for a DVB-T 2 MHz bandwidth signal. The DVB-T 2 MHz bandwidth allows using 4096-point iFFT math without the IQ stream exceeding the capacity of the USB2 interface. And the alias spurs magically disappear…see Figure 3 below.

DVB-T 2k mode using 4096-point iFFT
Figure 3 – Clean 2 MHz wide bandwidth for DVB-T 2k mode using 4096 iFFT math – with NO alias spurs

Figure 4 below shows the fine performance of the DATV-Express board being modulated with a minus 1MHz tone. The peak at the left is the intended LSB signal, the one in the middle is the un-suppressed carrier at 437 MHz and the one just above that is the unsuppressed USB. The signal to the far right is a harmonic of the modulating tone. So the board is getting 60 db carrier suppression and 52 dB unwanted side-band suppression and harmonics of -38 dB. This performance demonstrates how good the  phase/amplitude match is on the output of the DAC on the DATV-Express design..

unwanted side-band suppression
Figure 3 – An example of fine performance of hardware design suppressing an unwanted Upper-Sideband signal

The User Guide has been improved using feedback from early board users. The latest User Guide is now Draft34, and is available in the DOWNLOADs area.  If you have questions about capabilities of the board and software or are having questions setting up or using a board, please contact  our support team by using support@DATV-Express.com