ADALM-PLUTO (new DATV SDR)

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F1SSF
Posts: 73
Joined: Sat Nov 25, 2017 5:14 pm

Re: ADALM-PLUTO (new DATV SDR)

Post by F1SSF » Wed Jan 16, 2019 9:06 pm

Hi Charles,
I confirm that the V0.30 version continues to work with datvexpress, but I could not always operate the SR4000 It's limited, Time Clock on Minitioun is not locked. I have tested on 437Mhz and 1265Mghz.
For the SR2000, it is absolute perfect, Minitioun lock instantly.
73 Franck

G4GUO
Posts: 625
Joined: Tue Feb 16, 2010 12:51 pm

Re: ADALM-PLUTO (new DATV SDR)

Post by G4GUO » Wed Jan 16, 2019 9:31 pm

Franck,

I think it must be machine dependent as on my HP Pavilion I can get reliable 4.5 MS/s on the new firmware
but I can't achieve that with the old firmware.

The DATV-Express hardware will work up to 10 MS/s, at that point the anti-alias filters are starting to affect the performance.
The filters on the Express hardware were designed for a +/- 5 MHz bandwidth.

- Charles

M0SKM
Posts: 239
Joined: Sun Jul 13, 2014 3:15 pm

Re: ADALM-PLUTO (new DATV SDR)

Post by M0SKM » Wed Jan 16, 2019 10:47 pm

Franck/Charles

Updated mine just before our local net this evening; 4Ms/s was more stable with the new firmware.

During the net I used 2Ms/s but changed to 333Ks/s for a quick test; the result was a huge drop in power output from 15W down to 3W just on a symbol rate change.

We were chatting so I looked no further and switched back up to 2Ms/s, I'll check again tomorrow.

Anyone else found a problem?

73 Steve

g0mjw
Posts: 868
Joined: Sat Sep 20, 2014 9:15 am

Re: ADALM-PLUTO (new DATV SDR)

Post by g0mjw » Thu Jan 17, 2019 7:58 am

That could be explained if the power density remains constant - 2000 / 333 ~ 6 so it's about what you might expect if that were the case. I understand the Express over-samples as it has to do a lot more filtering to produce 333 as the nyquist filters on the board are designed for higher rates. If the same code is being used for the Pluto but without the over sampling, perhaps the filter gains need to be adjusted to compensate.

Mike

G4GUO
Posts: 625
Joined: Tue Feb 16, 2010 12:51 pm

Re: ADALM-PLUTO (new DATV SDR)

Post by G4GUO » Thu Jan 17, 2019 8:54 am

The oversampling is done in the Pluto itself, Express software always operates at 1 sample per symbol.
There is an issue with very low symbol rates due to the x8 interpolater in the Pluto's PL fabric which does not
have unity gain, I have to raise a bug report with Analog Devices apparently to get that fixed.

The Pluto works out what clock rate and oversampling are required itself. The interpolaters in the transceiver
chip are simple halfband filters so should have fixed hardware gains.

I am wondering whether the old firmware had the same problem or whether that is something new?

- Charles

dk9sas
Posts: 3
Joined: Sat Jun 02, 2018 7:57 pm

Re: ADALM-PLUTO (new DATV SDR)

Post by dk9sas » Thu Jan 17, 2019 12:17 pm

Charles, I have some strange audio/video hickup problems with DVB-S on my main system (QPSK, 2MSps, all FEC-Settings, H.264 with 10 GOP/0 B frames and superfast setting + 64kbps audio). The program only consumes about ~10% CPU when transmitting.

The h.264 encoder seems to overshoot in bitrate, since when there's a lot of new content in the picture the TX queue goes up. But that's not the main problem since audio stutter also occurs with a black screen transmitted. Fiddling with the "Video bitrate twiddle" (tried settings from 0.7 to 0.1) didn't seem to help much with the stutter but, displayed video bitrate got down to the expected 10th of the TX bitrate. TX queue was happily bouncing between 19% and 20% but the stutter continued. TX Hardware seems not to be the problem, tried Pluto and LimeSDr mini on different USB ports.

Tried the older version 25p11 but had the same problem.

Any idea what that could be?

73 Sascha

M0SKM
Posts: 239
Joined: Sun Jul 13, 2014 3:15 pm

Re: ADALM-PLUTO (new DATV SDR)

Post by M0SKM » Thu Jan 17, 2019 1:03 pm

Charles

This morning I reverted to the earlier firmware and made a comparison with v0.30, results are similar. Yesterday was the first time I had used the Pluto for transmit at low symbol rates; in fact it only came of the box in the last week.

Thanks for the information; I don’t really need it for lower symbol rates at present, it’s a stand in for the shack DTX1 which has developed a fault.

It will of course be great if Analog Devices can make improvements.

73 Steve

G4GUO
Posts: 625
Joined: Tue Feb 16, 2010 12:51 pm

Re: ADALM-PLUTO (new DATV SDR)

Post by G4GUO » Thu Jan 17, 2019 2:07 pm

Hello Sascha,

H.264 doesn't seem to have a CBR mode (constant bitrate mode) so what I do is set the max and min bitrates to the same value
to try and force it to do CBR.

I suspect the stuttering maybe due to a non compliant MPEG2 bitstream. This is a known problem with the Express software
and something I have been unable to fix (and I have tried very hard to fix it). It does not affect all receivers only those that
enforce full compliance to the standard.

You may like to try the Portsdown software and see if the problem persists with that.

- Charles

G4GUO
Posts: 625
Joined: Tue Feb 16, 2010 12:51 pm

Re: ADALM-PLUTO (new DATV SDR)

Post by G4GUO » Thu Jan 17, 2019 2:08 pm

OK Steve thanks for the information which is most helpful.

- Charles

radiogareth
Posts: 304
Joined: Wed Jan 06, 2016 9:46 am

Re: ADALM-PLUTO (new DATV SDR)

Post by radiogareth » Fri Jan 18, 2019 10:26 am

I have a pair of Plutos - having been waiting for 1 for nearly a year, once I got it (and used it with DATV Express and with SDR# up to 6GHz) I was so impressed I grabbed a second from somewhere in stock. Anyway, I have upgraded one to the latest 0.30 and its fine. Very quick to lock on 1255 so I tried 2395 - NOTHING transmitted although the TX queue and software remains in control. This is the same with both versions of Pluto FW. So I tried creeping back up the band from 1255. It seems I can get as far as 2380 and then no RF. Same with both units.
Has anyone else noticed this?
Its powered separately and has a short USB lead into a front USB3 on my desktop.

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