Monday, 24 December 2012

DATV-Express Roundup

I have not posted for a while about DATV-Express, don't worry the elves have been
busy working on it. Tom WB6P has been laying out the board and it is looking really
good. It is smaller and more densely packed than before. See 3D model above.

On the software front I have been playing around with DirectShow filters with some
help from Brian G4EWJ (of Digilite fame). I have managed to capture video using
a USB2 capture device (PVR-1900) then transfer it across the network to my Linux
machine which runs the DATV-Express software where it is transmitted as a DVB-S
signal  on 1249 MHz. I know that does not sound much but earlier in the week  I was
starting to get very worried that I wouldn't be able to get DATV-Express to work under
Windows. I already have the USB download of firmware to the Express board working
under Windows and the last unknown was how to get the captured video into a program.
I am now happy it can be done.

It would be really neat to write the DATV-Express software as a DirectShow filter,
then using GraphEdit (or alternatives) people could make drag and drop transmitter
chains using different codecs and capture devices. I have never written a DirectShow
filter so whether I will do that I don't know yet. The first Windows version will probably
be a clone of the Linux version.

Seasons greetings to anyone that reads my blog and fingers crossed, 2013 will be
the year of DATV-Express.


  1. Thanks for the updates. Looking forward to building one.

    Mike KM7MH

    1. Hello Mike, I am not sure how viable it will be to build one.
      The PLL/Modulator chip is a real pig to solder. However all
      the prototype boards so far have been hand soldered. I will
      certainly press for blank boards to be made available. All
      the parts are available from Digikey for the brave!

      - Charles G4GUO

  2. Hi Charles,

    Don't know what I was thinking, most SMT boards do come stuffed. Old school, build it from the ground up dies hard. My first FM ATV TX & RX were all home brew with discrete components, how things have changed.

    I find it a strange dichotomy that near vision degrades with age as components get smaller and smaller. SMT resistors the size grains of salt.

    Mike KM7MH

  3. Hi Mike,
    If you have all the gear it can be done and there are people out there mad enough to want to try. Having the boards assembled only costs a few dollars extra per board on a large batch. 95% of this
    project is software and that is something hobbyists can still home
    brew. To me the hardware is something that enables people to write creative software. I know that is not to everyone's taste but it is the way all technology is moving. There is always the PA etc to build. P.S I did build Heathkits when younger (showing my age now).

    1. Hi Charles,

      I remember getting hooked on the software side of things the first time I programmed a PIC processor to run a PLL. Sure beat selecting frequency by diode matrix.