DATV-Express Project

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G8GKQ
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Re: DATV-Express Project

Post by G8GKQ » Mon Jul 30, 2018 5:07 pm

Reference GPIO Interfaces.

I'm not sure that we need to re-invent the wheel on this one. The DATV Express and the Portsdown both have GPIO outputs that can be driven by the transmitter software: Charles's excellent software on Windows or Linux for the DATV Express, and the Portsdown software on a Raspberry Pi which drives either the DATV EXpress GPIOs or the RPi GPIOs. Potentially either software could drive the Lime GPIOs.

The Portsdown design includes 4 channel+PTT and 8 channel+PTT switching boards with opto-isolators which have been in use for over a year now with no reported GPIO damage. Details here: https://wiki.batc.org.uk/PTT_and_band_switching and here https://wiki.batc.org.uk/8-Band_Decoder. Companion RF switches are also described; PCBs and the PIC are available from the BATC Shop.

I suggest that we standardise on this sort of interface (3v3 or 5v GPIOs, one line goes high for PTT, and 2 or 3 lines sending a binary code for band selection. The current Portsdown standard (which is also used for Portsdown driving DATV EXpress boards) is 0 for 71 MHz, 1 for 146 MHz, 2 for 437 MHz, 3 for 1255 MHz and 4 and above for transverters.

Dave, G8GKQ

KenW6HHC
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Re: DATV-Express Project

Post by KenW6HHC » Wed Aug 01, 2018 3:04 pm

Art WA8RMC reports that during July, most of his sales of MiniTiouner-Express receivers occured outside the U.S. Art also reports that there will be a pause in shipping MiniTiouner-Express units from USA from August 07 through August 18, while Art enjoys a vacation. Charles reports there are currently five units in inventory for shipments to customers in the European Union.

Ken W6HHC reports that the NOTES file for DATV-Express v1.25LP9 software has been updated to show a SR comparison among the four supported hardware boards.

The Symbol Rate supported by the four exciter boards varies and all rates show below are dependent on how fast is the CPU and the USB-architecture of your computer. The approximate SR maximums (or achievable channel-RFbandwidth for DVB-T protocol) are shown below:
  • EXCITER...………………………….DVB-S...……………….DVB-S2...……………….DVB-T
    DATV-Express (USB-2)……...100K-20M S/sec …..100K-20M S/sec...…..2 MHz-7 MHz RFbw
    LimeSDR (USB-3)……………….100K-20M S/sec …..100K-20M S/sec...…..2 MHz-7 MHz RFbw
    Lime SDR-mini (USB-3)……..100K-20M S/sec ....100K-20M S/sec...…..2 MHz-7 MHz RFbw
    PLUTO (USB-2)…………………..100K-~2M S/sec....100K-~2M S/sec...…..2 MHz RFbw
The NOTES file can be downloaded from the www.DATV-Express.com web site on the DOWNLOADS page.

Charles G4GUO reports that he has been spending a lot of time designing an RF amplifier for the newly opened 70.5-to-71.5 MHz DATV band in England.

Project Speed is set to slow….de Ken W6HHC

G4EWJ
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Re: DATV-Express Project

Post by G4EWJ » Thu Aug 09, 2018 1:40 pm

I've just tried 1.25LP9 for the first time. Thanks Charles.

When adjusting the TX power setting with the cursor keys, the slider moves, but the power output doesn't change. Hitting ENTER at this point causes the program to exit. It's handy to have the cursor option when under adverse working conditions.

Clicking PTT to turn off a transmission leaves a carrier being emitted.

Clicking PTT to go back to transmit after changing a setting causes a re-calibration, but transmit is not activated. You have to click PTT again.

Re-calibration occurs for changes of non-frequency settings - e.g. FEC.

Using W7PRO64.

Brian

G4GUO
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Re: DATV-Express Project

Post by G4GUO » Thu Aug 09, 2018 3:32 pm

Hi Brian,
The problem is that when the power level is changed the the IQ
magnitude/phase balance changes so a re-calibration is required if
you want to maintain the EVM/MER. Yes it also does re-calibrate when
not necessary which is because I simplified the state table that
decides when to re-calibrate (laziness).

As far as a carrier being present on receive. I suspect it is at a low level
as I turn down the transmitter gain rather than stop the transmitter.

You will also find than when you use 16APSK and 32APSK you have to
turn back the level due to the increased peak to mean ratio of those modes.

As far as Lime is concerned, I am waiting for them to sort out their
firmware before I do much as it is a moving target, new builds of
Express are required every time they update Limesuite.

- Charles

G4EWJ
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Re: DATV-Express Project

Post by G4EWJ » Thu Aug 09, 2018 6:21 pm

Thanks Charles.

I should have said that I'm using a Pluto. The carrier level after transmit off is at the same level as for transmit on.

Brian

G4GUO
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Re: DATV-Express Project

Post by G4GUO » Thu Aug 09, 2018 8:45 pm

OK Brian, well that is wrong :(
I am not sure when I can look at it, just too many things to do.

- Charles

KenW6HHC
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Re: DATV-Express Project

Post by KenW6HHC » Fri Aug 10, 2018 6:48 pm

I do not normally use cursor-keys to change the RF-power-level-slider when using DATV-Express v1.25LP9 software...so I retested what Brian G4EWJ described in his posting about using the PLUTO board as the exciter.

1) Brian is correct, v1.25LP9 software the RF-power-level-slider can not successfully use curser keys to move/change the power-out level. The slider moves position with the cursor-keys. but the actual RF power out does NOT change. This bug affects all the exciters: DATV-Express, LimeSDR and PLUTO. The work-around is easy, grab-and-move the slider bar with your mouse.

2) Brian is also correct that with PLUTO, clicking PTT on the GUI to turn off a transmission leaves a "same level" RF carrier being emitted. This v1.25LP9 software bug does NOT affect the DATV-Express or LimeSDR-mini boards.

Bryan G4EWJ thanks for your feedback...de Ken W6HHC

KenW6HHC
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Re: DATV-Express Project

Post by KenW6HHC » Wed Sep 05, 2018 6:02 pm

Art WA8RMC reports that there was a steady stream of orders during August for MiniTiouner-Express receivers. Many of the orders are for customers in the European Union…..and Charles is now waiting for more units to arrive from Art (that is clear customs), in order to resume shipping to EU orders.

Charles G4GUO has fixed one bug for PLUTO units and has prepared a zip of v1.25LP10 software for Ken to test,

Ken W6HHC reports he has just received a v1.25LP10 zip file from Charles for the Windows DATV-Express software. This software corrects a small (code-wise) bug in the PLUTO support that allowed an RF-carrier to be produced in RECEIVE mode after the PTT button was released from TRANSMIT. Ken plans to begin testing the new software version on PLUTO, and LimeSDR-mini, and DATV-Express hardware units before uploading to the www.DATV-Express.com web site on the DOWNLOADS page.

Charles G4GUO also reports he has been spending time lately working on “pre-distortion” software for the DATV-Express software, that lower the distortion “shoulders” on the hardware RF output. The status is that he has sorted out a non-obvious math problem and is now moving in a positive direction for this new DATV feature.

Project Speed is set to slow….de Ken W6HHC

KenW6HHC
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Joined: Mon Jun 01, 2009 4:20 pm

Re: DATV-Express Project - v1.25LP10 available

Post by KenW6HHC » Thu Sep 13, 2018 1:31 pm

Just a note that the v1.25LP10 software (DATV-Express DVB Transmitter software for Windows) is available for download.
This build of software fixes the PLUTO problem where an RF carrier is sent out when clicking PTT to go back to STANDBY.
This software now supports four hardware exciter boards:
  • DATV-Express (USB-2)
  • LimeSDR (USB-3 or -2)
  • LimeSDR-mini (USB-3 or -2)
  • PLUTO (USB-2)
The software can be downloaded from the project web-site at www.DATV-Express.com . Go to the DOWNLOADs page.
A stand alone NOTES file (aka README) can also be downloaded from the same DOWNLOADs page.

Many thanks to Charles G4GUO for correcting the PLUTO “unexpected carrier” bug…de Ken W6HHC

G4GUO
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Re: DATV-Express Project

Post by G4GUO » Tue Oct 02, 2018 11:29 am

If anyone is using a LimeSDR-USB on any frequency or a LimeSDR-Mini above 2 GHz you need this
https://www.dropbox.com/s/u8irxtjz5j3qj ... 1.zip?dl=0

Thanks to John G4BAO for reporting the problem and testing it for me

- Charles

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