Portdown 4 no DVB-S/S2 tx

Discussion about this major DATV Project. See https://wiki.batc.org.uk/The_Portsdown_Transmitter
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pe1itr
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Joined: Tue Jan 21, 2020 10:26 pm

Portdown 4 no DVB-S/S2 tx

Post by pe1itr » Tue Jul 19, 2022 10:13 pm

I have the following issue which I am hoping someone can help me figure out the problem with.
I have a fresh portsdown 4 install with a pluto. All correct firmware is loaded. I can transmit with DVB-T, but with the option DVB-S or DVB-S2, the pluto will not transmit. I read in the documentation that audio for S/S2 should be on and as far as I can see it is.
When I address the pluto directly with OBS, DVB-S works normally. How can I find out what's going wrong?

73 Rob PE1ITR

radiogareth
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Re: Portdown 4 no DVB-S/S2 tx

Post by radiogareth » Wed Jul 20, 2022 7:24 am

I have found that I need to re-boot after using DVB-T to get DVBS-2 to work - everything 'seems to work' but no proper signal comes out.....
DVBS-2 to DVB-T seem ok, but not 'back the other way'....
Gareth

pe1itr
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Re: Portdown 4 no DVB-S/S2 tx

Post by pe1itr » Wed Jul 20, 2022 11:02 pm

I have DVB-S/S2 in operation now. The solution was to feed the Pluto with a separate power supply and not via the rasppi4 usb port.
However, a special method of treatment is required. I can broadcast DVB-S/S2 directly, but if I go to DVB-T and then switch to DVB-S/S2, the DVB-S/S2 transmitter will not turn on. The pluto then needs a reboot to go to DVB-S/S2.
73 Rob

G8GKQ
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Re: Portdown 4 no DVB-S/S2 tx

Post by G8GKQ » Thu Jul 21, 2022 9:04 am

Hi Rob

That is interesting.

I have noticed that th Pluto is less reliable for DVB-S/S2 when supplied with more than 5.0 v on the data USB port. Please could you check the voltage that you are using on the Pluto power port to help us investigate?

Using the Pluto for DVB-T stops the on-board software that runs DVB-S/S2. Rebooting the Pluto restarts this software. I wish i could find an easier way to restart the DVB-S/S2 software.

Dave

pe1itr
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Re: Portdown 4 no DVB-S/S2 tx

Post by pe1itr » Sat Jul 30, 2022 8:54 pm

Hi Dave,

I measure 5.01 Volts.
I found out that the USB problems also depended on where I had the transmitter on the workbench. Also when I connected a spectrum analyzer the pluto stopped transmitting. It seemed more like an earth problem to me.

When you google "Pluto ground mod" on the internet you will see more of these kinds of problems with the usb. In this modification, the minus of the USB power connection is connected to the minus on the PCB. I have done this modification and now the pluto works without problems with the Portsdown 4. Even when I power the Pluto from the usb port of the Raspberry PI4.

73 Rob PE1ITR

I used this mod:
https://www.f5uii.net/en/transmit-datv- ... lutodvb/4/

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M5TXJ
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Re: Portdown 4 no DVB-S/S2 tx

Post by M5TXJ » Mon Sep 19, 2022 6:00 pm

I was having issues where I was having to reboot the Portsdown if I changed frequency, SR or FEC, Menu 3 Pluto reboot just didn't work. I've done the ground mod and also cut into the USB cable adding a 1N5817 Schottky diode in series with the power wire. The butchery has been covered with copper foil from a scrap of mini 8 coax. The Pi is now running at 5.15v and the Pluto 4.85v. It's early days but all seems good so far.

73 Dave
...are you sure I can't use a pair of 813's?... :shock:

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M5TXJ
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Re: Portdown 4 no DVB-S/S2 tx

Post by M5TXJ » Mon Sep 26, 2022 6:32 am

Update,

I can confirm that adding the 1N5817 diode to the 5v wire in the USB cable has been a great success. If you have a Portsdown/Langstone combo where the Pluto is powered from the Pi via the USB lead and are having Pluto disconnection issues this could be for you. The Pi wanting over 5V and the Pluto wanting less than 5V yet being connected by USB doesn't have to be a "Catch 22" issue.

73 Dave
...are you sure I can't use a pair of 813's?... :shock:

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