Improving the LimeSDR Performance with Portsdown Buster

Discussion about this major DATV Project. See also https://wiki.batc.org.uk/The_Portsdown_Transmitter
G0LJF
Posts: 17
Joined: Wed Dec 25, 2019 5:28 pm

Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G0LJF » Mon Feb 17, 2020 11:09 am

Dave,

I am only having problems with the P2020 SW operation now.
Buster and P2020 software is now installed and running OK. There are these problems.

a) Display will not rotate unless you select rotation and reboot about three times (it does eventually work). Reported already.

b) I did run your script on RPi to correct the Lime V1.30 firmware issue in the P2020 install, as reported already.

c) Zero, well 0.5 to 0.25 mW RF maximum output on 437MHz and 2.4GHz. Seems a bit weedy. No idea about any picture, did not check.

d) Seems to only produce any RF (barely, see (b)) when sending to LimeMini. Should this be LimeDVB instead? Do I select LimeMini or LimeDVB as the output? Is this just a Lime firmware difference, not hardware?

e) Lime firmware update sometimes fails.

f) Please can you let us know what versions on Lime firmware we are supposed to use and how to check for this in P2020. I only ever get two "Gateway" versions 29 or 30 reported and yet there are three Lime firmware update buttons for "1.29", "1.30" and "DVB".
Your instructions say install version 1.30 and THEN the DVB version? Why? Does one not overwrite the earlier one?

g) Lime report shows several self-test failures now, as reported previously.

What is this "Gateway" and how can I tell if the DVB firmware is installed at all from the Lime Report, does it have any numerical ID? Answered this myself... this "DVB" version comes from F5OEO and he has called the release "0.3". The other two are from Lime.
F5OEO has reduced the USB message size to the LimeSDR by 20 bytes. I see. Well I am having no luck here, regardless.

Ta, but I do not know anything about the Lime firmware versions and how to make sure I have the right one.

I think my remaining problem is only with the Lime firmware version or what appears to be referred to as a "Gateway".

Thanks, 73,

Mike
Last edited by G0LJF on Mon Feb 17, 2020 12:11 pm, edited 2 times in total.

G8GKQ
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Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G8GKQ » Mon Feb 17, 2020 12:06 pm

Hi Mike

Quick comments, as I am writing the how-to guide at the moment!

a. I have made some progress on the troublesome display rotation, but not fixed yet.

c. Output is about this level (-3 dBm) with default Lime Gain. Increase Lime Gain towards 100 to get more RF. It is not unusual for SDRs; the Pluto only gives about a tenth of this.

d. If you have the LimeDVB firmware loaded, you MUST select LimeDVB as the Portsdown output mode. If you have bare 1.30, you MUST select Lime Mini (mode not tested yet). You cannot mix the selections.

e. Have not seen the Lime Firmware update failing after running the correction script. Please provide more details.

f. I have only tested LimeDVB so far, so you should use LimeDVB firmware and LimeDVB output selection. The LimeDVB firmware partially overwrites the previously loaded firmware (complete overwrite of processor image, which then partially overwrites gateware, is my understanding).

Gateware is the configuration of the FPGA on the LimeSDR Mini.

Thanks for the SD Card writing info. I'll move that to a separate topic.

Dave

G0LJF
Posts: 17
Joined: Wed Dec 25, 2019 5:28 pm

Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G0LJF » Mon Feb 17, 2020 12:20 pm

OK Dave, ta,

I am still at a loss to getting any RF output today...Cannot see the needle moving at all.

Will try re-flashing my Lime yet again, in the correct sequence, and also selecting LimeDVB as the output device, as you say. Will try maximum 'volume' on the Lime gain too.

Odd that the output power is now -3dBm as it WAS about 6dBm with P2019 (Lime gain 88). Let alone the calibration stage that blasted my little meter needle!

Ta,

Mike

G0LJF
Posts: 17
Joined: Wed Dec 25, 2019 5:28 pm

Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G0LJF » Mon Feb 17, 2020 12:38 pm

OK, Dave,

Success. My problem was all these three...

a) Making sure the right two Lime firmware were flashed, in the order of "1.30" THEN "LimeDVB" and
b) selecting "LimeDVB" as output device, and WORST of all
c) not noticing that the RF output is now very, very, low with a Lime Gain of 88.

Set the Lime gain to 100% or you see nothing (on my little diode mW meter) is my advice.

Ta, 73,

Mike

Nick
Posts: 72
Joined: Sat Oct 03, 2015 10:09 am

Re: Improving the LimeSDR Performance with Portsdown Buster

Post by Nick » Mon Feb 17, 2020 1:19 pm

Hello,

I'm I correct in saying that this new configuration of the Lime reduces RF output ?

I have no upgraded software for a while, but my measurements at 2400MHz are:-

Lime Gain 88 - carrier output 6.35dBm.
Lime Gain 100 - carrier output 15.75dBm.

These measurments were made at the output of the 8 way RF switch, not the Lime itself with the attenuator set at 0dB.

Just wondering if I will require a bit more RF amplification in the Poertsdown itself to drive the main amplifier.

Regards,

Nick - G4NKV.

G0LJF
Posts: 17
Joined: Wed Dec 25, 2019 5:28 pm

Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G0LJF » Mon Feb 17, 2020 3:28 pm

Hello Nick,

I agree with your 2.4GHz (88) power values on P2019.

With my vast experience (1/6 of a day, today) with P2020 (Buster) I am getting about 4-6 mW maximum output with all attenuators off now, LimeGain now must be set to 100.

This is less than before with P2019 (set to LimeGain 88). Dave C please correct me if I am wrong...

This is measured by a simple diode probe and moving coil voltmeter, so not calibrated, but shows the number of mW, fine, for low (up to 100s MHz) frequencies OK.

I have no tried my high-frequency Schottky diode RF detector on 2.4GHz yet, but you get the idea.

Nor have I connected up any 2.4GHz amps - my experience is very brief so far.
I use an EDUP booster amp just to get to the next room where the main PA is.

73, Mike

G8GKQ
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Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G8GKQ » Mon Feb 17, 2020 4:38 pm

During early testing, I estimated that the power output form the LimeDVB software at Lime Gain 100 was 4 dB less than the line on this chart https://wiki.batc.org.uk/LimeSDR_Mini_O ... wer_Levels which was drawn up using the older software at Lime Gain 88.

Dave

G8GKQ
Site Admin
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Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G8GKQ » Mon Feb 17, 2020 6:06 pm

I have corrected the "7 inch Screen Fails to Rotate" bug in the latest build (202002141). You can update through the normal process (Menu 3, Check for Update).

I have also written a Portsdown 2020 Getting Started Guide https://wiki.batc.org.uk/Portsdown_2020 ... rted_Guide which will hopefully answer many of the questions that have arisen over the last few days. Please read it and make/suggest amendments and additions.

Dave, G8GKQ

G8KOE
Posts: 28
Joined: Fri Aug 09, 2019 8:14 am

Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G8KOE » Mon Feb 17, 2020 9:44 pm

Hi Dave,
Thanks for the Portsdown 2020 Getting Started Guide very useful.

73's
Martin

G0LJF
Posts: 17
Joined: Wed Dec 25, 2019 5:28 pm

Re: Improving the LimeSDR Performance with Portsdown Buster

Post by G0LJF » Tue Feb 18, 2020 10:39 am

Hi Dave,

This start-up guide is just the thing for newcomers - Ta.

The 125K spectrum IS cleaner from what I can see on my SDR Rx (so far).

I already find this release is a big improvement on P2019 Tx reliability.

I would recommend an upgrade, from P2019, if you need a more dependable Tx output, and that all the input devices I tested (PiCam, Video Capture, Test Card and Animated CQ Test Card, as well as that "Portsdown" static display) now appear to function well.

I will try to log any 'problems' I find, for another time. I am still checking things out here.

These may just be solely due to my setup, or my error, of course!

73, Mike

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