portsdown Tx description

[Richard-g8jvm]

before the RTFM, I have read the wiki

What in Tx mode is the exact function of the RPi4, OK video in, but what format is being passed to either Pluto, Lime or DATV Express, ?
and what functions of the PLuto etc, are actually used.?
Up conversion to final frequency is low cost , so why are all three so expensive ?
my whole philosophy since first licensed in 1974, is if it looks expensive build it, as it doesn't need to be in a pretty box.
73 Richard g8jvm

[g0mjw]

The PI4is encoding the video and audio into a compressed format, typically using H264 for the video and AAC for the audio so going down to perhaps 400kb/s or so. That's then sent to the Pluto, via a virtual IP interface, which formats it into an MPEG transport stream, adds the forward error correction and modulates it as an appropriately filtered QPSK signal at whatever frequency is needed between about 50 MHz and 6 GHz.

The Pluto with F5OEO firmware also accepts an MPEG TS input via UDP, which you can generate on a PC, so you don't strictly need the PI.

The Pluto is a software defined radio, it is doing a lot to generate that signal and I don't think it is expensive considering what it is doing. If you add up the cost of the parts inside, it comes to more than the cost of the unit, so I don't know how they make them for the price. I have no idea why the LimeSDR is now so expensive, it used to cost about the same as a Pluto, but is not a viable option these days.

The world has moved on quite a bit since 1974.

Mike

[Richard-g8jvm]

Many thanks for the concise description Mike. Exactly what I was looking for.
The pluto is doing a fair bit of number crunching then.
However there is what seems to be a Cartel operating in the UK .
It seems no-one is selling at less than the UK AD price, Digikey US and Mouser US are selling at substantially less than Digikey uk or Mouser UK,.
As with Farnell and RS with their US counterparts.
However, Aliexpress are offering the Adalm-Pluto/AdalmM1000 around £110, so even with ransom tax costing a lot less, also some Chinese clones costing less.
Is the Adalm-Pluto/AdalmM1000 the same as being used with the Portsdown Tx?
Has anyone purchased from Aliexpress, and did they get caught for customs duty and ransom tax ?

I am very aware things have changed from 1974, technology has improved, but technical capability has moved in the opposite direction, so many now dont even know what a soldering iron is , let alone know which end gets hot. At least in BATC there should still be those that know that if there smell bacon cooking, its either food or they have burnt themselves with a soldering iron.
73
Richard g8jvm

[G3GJA]

The cheapest source of the ADALM Pluto is Digikey UK. Expect to pay around £225 in total.
Carriage and VAT is paid by Digikey. That won't be on the US sites.
They are fast too; order today and it will be with you on Thursday, sometimes a day less.
Make sure you use the UPS carrier option in the checkout; as that ensures you don't get hit by importer handling charges.

ADALM 1000 is a totally different product that has no RF capability.

73
Clive G3GJA

[radiogareth]

Richerd, AliExpress is very good these days, what you pay is generally cost +'delivery' and then VAT on the whole lot. They have excellent tracking and a robust 'are you happy' with the goods. Can't comment on their Pluto offerings, but generally ordering from US Digikey or Mouser is cheaper than any of the UK outlets.
Even at UK RRP, the Pluto is a remarkable piece of kit. When you consider Portsdown, Langstone (and soon SDR COnsole for TV) plus the amazing SATSAGEN software its a bargain.
Some of it is 'horses for courses' but the BATC has a good percentage of avid constructors and experimenters which overlaps wonderfully with the microwave community.
I operate under several 'mottos', not least 'Tis in vain to do with more, that which can be done with less' and 'If it solves the problem, use it'.
Gareth

[G8GKQ]

Hi Richard

I would recommend buying a "real" Pluto from DigiKey UK.

The Chinese clones have far worse spurious emissions and worse spurious responses on receive. You won't only use it with Portsdown or DATV modes. Have a look at SatSAGen https://www.albfer.com/en/2020/02/21/satsagen-2/. An amazing capability. And of course it works with Langstone (which can be integrated with the Portsdown build).

In answer to your earlier question, the Portsdown sends an RTMP video stream to the Pluto. The on-board processor in the Pluto converts this into a DVB video stream and then converts this into the IQ samples required to modulate a carrier to produce a DVB-S2 signal. There is no up-conversion in any of the SDRs that you mention - they all apply the modulation to a carrier at the output frequency.

The Lime and DATV Express work differently in that the DVB-S2 IQ samples are generated in the Portsdown and passed to the SDR over USB.

The only glitch with the Pluto/Portsdown configuration is that it is best run with an external power supply to the Pluto, or less than 4.9v if powered from the Raspberry Pi. Note that the correct firmware has to be loaded into the Pluto for what you want it to do.

Dave, G8GKQ

[G3GJA]

Be careful with AliExpress.

Gareth may have had a good experience , but the Pluto sourcing from there looks like a minefield.

The headline price might look attractive and the picture is correct but when you dig further the price is for the cheaper ADALM 1000. If you then click on the Pluto image the price is far more than you would pay from Digikey.

Other vendors are offering 'compatible' PCBs only.

Bottom line is if you want a genuine Pluto it will cost you £225. Caveat emptor!

Clive

[g0mjw]

Many thanks for the concise description Mike. Exactly what I was looking for.
The pluto is doing a fair bit of number crunching then.
However there is what seems to be a Cartel operating in the UK .
It seems no-one is selling at less than the UK AD price, Digikey US and Mouser US are selling at substantially less than Digikey uk or Mouser UK,.

There isn't a cartel, the price in the US and UK is the same, what is different is the tax. Digikey UK currently has it for £216 including VAT and delivered. The price on Digikey US is $233.25 - that's £180 which when you add VAT is £216.

Mike

[Richard-g8jvm]

Thanks for the replies and I've had a close look at Aliexpress
now way to contact dealers before hand, and as You say Clive they are mixing the M1000 in as well.. I'm always suspicious of anything from China, albeit
the Pluto is probably made there , so it could be local sourcing, or even from the rework area at the end of the line.
I suspect that with the current occupier of the White Hse, tariffs will screw the prices up, as AD will ship from the point of manufacture to it main warehouse, USA, then on to distributors.
I'm aware Gareth has had good buys from Aliexpress, 3.4GHz sspa's , and the MAX2870 boards look OK, but I'll take the advise and get one from Digikey UK, I've used them before and never any problems
73 Richard g8jvm

[Richard-g8jvm]

Just ordered one from Digikey
Richard