Tuesday, 11 June 2013

DATV-Epxress update for May/June 2013

I was having some problems with DATV-Express, initially I thought it
was the software and spent a couple of weeks debugging it to no avail.
I was starting to get a bit desperate and doubting my own sanity.

In the end I found there was a dry joint on one or more of the FPGA pins.
I have re-soldered the chip and now it is all working much better. there is
still a minor issue with the Kernel USB drivers where it seems to loose all
knowledge of the capture card and DATV-Express if the program closes badly.
That is a minor issue.

There are two strands to the DATV-Express software, one is the Linux
QT5 program that you all know about. The other is a much simpler program
that only implements DVB-S that will run on a Raspberry PI or other ARM
based board. The second program is aimed at portable operation or use in
repeaters as no heavy PC will be needed to use it. The second program
is also very modular and I hope hackable by others.

I have install a GIT server on my Synology Network Disk Server and I already
have a GIT depository of the smaller ARM based program on it. In the next few
days I will put the QT5 program under GIT management. Eventually these two
repositories will be moved to a public server for people to download and play with.
All this GIT stuff is new to me and I am making many mistakes along the way
but that is the way to learn about things.

We have decided to make one more version of DATV-Express before we go
into production. The analogue tracks from the DAC to the IQ modulator need to
be made as symmetrical as possible to improve unwanted sideband supression
and we need to improve the cooling of the modulator chip as it gets very hot.
This is an issue with the chip itself and not our design. Apart from that a few
resistor values need to be changed to simplify the inventory.

We are still on track to make the first boards available to brave early adopters
around the time of the BATC convention in October. We are not sure how many
boards will be manufactured yet as it will involve a significant cash outlay.
A large batch significantly reduces the per unit cost but is quite risky on the
first run.

We thank everyone for their patience as you know this is being done on a not for
profit basis in our spare time and hence the long time scale.


  1. "We are not sure how many
    boards will be manufactured yet as it will involve a significant cash outlay.
    A large batch significantly reduces the per unit cost but is quite risky on the
    first run."

    Go ahead and take my money up-front. Where do I place an order/pay?


  2. Hello Herman, thanks, we made a decision at the start
    of the project not to take pre-orders. If we do a small
    batch the boards will be about $50 more expensive than if
    we do a large batch. What we will probably do is have a
    few new boards made, verify the layout is correct then go
    for a larger batch. We are also looking at Amateur Radio
    applications outside ATV, like cheap test equipment or
    as a narrowband exciter.

  3. Fair enough Charles. Use my comment for what it really was; an indicator of strong interest and confidence. I think you guys are absolutely right in seeing applications beyond DATV. I noticed several new entry-level RF DSP HW initiatives last few months (Myriad-RF, BladeRF) that are received very enthusiastically amongst educators and hobbyist.


    1. The reason we made a decision not to take money up
      front is we didn't want to get into the situation
      where we had all this money and no product and we
      had to return the money. This has happened on at
      least one project I know of.

      I was tempted to put my name down for a Blade but
      I already have a USRP2. Shame the magic chip costs
      $100 in single off quantities.

      As it has been mention in the BATC CQ-TV magazine this
      month I can tell you that the BATC will be selling
      DATV-Express in Europe. We have not finally decided on
      a U.S distributor yet.