Improving the LimeSDR Performance with Portsdown Buster

Discussion about this major DATV Project. See also https://wiki.batc.org.uk/The_Portsdown_Transmitter
G8GKQ
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Improving the LimeSDR Performance with Portsdown Buster

Post by G8GKQ » Thu Feb 13, 2020 10:19 pm

The new Portsdown Buster build is designed to be used with the LimeSDR Mini running custom DVB firmware. I have now completed initial testing of this build (202002140) and am pleased to report that it resolves many of the issues (some modes not working, transmission breaks, etc) of the old Portsdown Stretch build.

Additionally, it supports the transmission of high SR DVB-S transmissions (up to 10 MS, if you must), so is suitable for transmitting to many of the existing ATV Repeaters. The usable DVB-S2 SR is limited to about 2 MS.

The one drawback is that the LimeSDR Mini needs to have the custom DVB firmware loaded, and so cannot be instantly used to transmit with other applications such as SDR Console. However, you can reprogram the firmware easily back and forth (Menu 3, Lime Config) and it is EEPROM based, so each LimeSDR Mini has a lifetime of at least 10,000 re-writes.

I have optimised the DVB-S2 modes for QO-100 use. The 333 KS FEC 1/2 transmission will transmit good SD pictures and only needs 1 dB S/N for reception, so can be transmitted with lower power or a smaller dish. The video source can be the Pi Camera, the EasyCap (Composite Video) or the C920 webcam.

There is no upgrade path from Stretch - you will need to build a new SD Card. There is a Wiki page listing the working modes here https://wiki.batc.org.uk/Portsdown_2020_Buster_Software and the build instructions are here https://github.com/BritishAmateurTelevi ... own-buster.

Modes not listed on the Wiki page have not been tested, so please don't complain that they are not working. The software will not support the LimeSDR USB, webcams other than the C920, or the Raspberry Pi 4. It is hoped to support the LimeNET Micro and LimeRFE amplifier as development progresses.

Please report your experiences with this build in this topic.

Dave

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Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G0LJF » Fri Feb 14, 2020 11:29 am

Hi Dave,

Thanks for this update to P.

Please, seeing as I have just constructed a brand new P2019 with the latest Stretch build, would you now be advising me to go straight to this Buster release?

The reason I ask may sound stupid, but I am having problems making sure a particular mode in the exiting Stretch build does not drop Tx power and is, above all, reliable. It it does not work at all that is fine.

This is because all my other stuff (the technical phrase) is also new and I need to know what I can really rely on.

To date I have had to put my diode probe RF detector on P2019 to check if it is reliable in terms of Tx power before doing any other system testing, if you follow me.

Ta, 73, Mike

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Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G8GKQ » Fri Feb 14, 2020 12:23 pm

Hi Mike

The answer is "it depends". If you are using a Pi Cam as your video source with a LimeSDR Mini, then all should be fine on the Portsdown 2019 build. Other video sources do suffer from power drops, but if you stick to the green squares here viewtopic.php?f=103&t=6070#p19583 they are not too bad.

If you want to transmit to DVB-S2 to QO-100 using a Lime SDR Mini, then I would recommend that you use Portsdown 2020 on Buster, as that seems to be working perfectly with the Pi Cam, EasyCap (Comp Vid) or C920 as video sources. You will need to change the firmware on the LimeSDR Mini. This is easy and the instructions are on the Wiki page.

Perhaps if you describe what you are trying to achieve, and with what gear, I can give some more direct advice.

73

Dave

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Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G0LJF » Fri Feb 14, 2020 1:34 pm

OK Dave, Tnx,

I am working on Es'Hail2 exclusively, and so I think you have answered my question.

I have just bought another San Disk Ultra 16 GB card so will 'make' another SD card build now.

My problem is the lack of Tx reliability with Stretch; I initially thought that an external video source would be good (as I can just leave that playing, reliably, while I test things out). However, this is unreliable, as you no doubt know.

So I had to go for the PI Cam instead.

I could not get any decode at at all with 66 Kb Symbols/s Tx by the way (Pi Cam). MT Pro just shows a "X" on the constellation display, so that seems like a no-go option?

I am going for a full Buster build now...

Thank you, 73,

Mike

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Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G8KOE » Fri Feb 14, 2020 9:44 pm

Hi Dave,
Is vMIX supported in the new image?

73's
Martin
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Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G8GKQ » Sat Feb 15, 2020 11:46 am

Hi Martin

vMix input is not something that I have tested or tried to do. Was it possible in Portsdown Stretch?

Dave

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Re: Improving the LimeSDR Performance with Portsdown Buster

Post by g8gtz » Sat Feb 15, 2020 12:41 pm


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Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G8KOE » Sat Feb 15, 2020 12:47 pm

Hi Dave,
Yes works with no problems using the batch file "Feb 2019 by Evariste F5OEO - QO-100 Release 0.9"
Using an i7 Dell computer to run vMIX.
Would be very useful to me.
The NDI Desktop Capture function in vMIX makes it easy to stream images etc from any computer on network.

Just formatted a card and copied Buster onto it.

73's
Martin
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Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G8KOE » Sat Feb 15, 2020 5:55 pm

Hi Dave,
Programmed the SD all OK
Updated the Lime Mini to LIME-DVB firmware.
Could not get the lime to drive my amplifies.
I managed to see a poor signal locally as though it was very low power from lime.
Also tried the 1.29 and 1.30 with same results.
The Lime Test Report had three failures.
Also couldn't change memory 1
I have put my original SD card back all now working.

Sorry I failed now time to sit in dark room.

73's
Martin
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Re: Improving the LimeSDR Performance with Portsdown Buster

Post by F4DVK » Sun Feb 16, 2020 7:25 am

Hi Dave,

The install file is incorrect for downloading firmware 1.30:

mkdir -p /home/pi/.local/share/LimeSuite/images/20.01/
wget https://downloads.myriadrf.org/project/ ... _r1.30.rpd -O \
/home/pi/.local/share/LimeSuite/images/20.10/LimeSDR-Mini_HW_1.2_r1.30.rpd

Stephane.

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