Open Research Institute Weekly Reports, 2 Jun 2021

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From YouTube: 20210602 Multimedia DVB S2X 10GHz Beacon

Description

Here's a progress update on our multimedia beacon project, going on the air at 10 GHz and providing advanced digital broadband microwave opportunities for people interested in learning more about DVB-S2/X transmit and receive.

Codenamed BeacRon, in honor of Ron Economos, who advises the work, the project transmits a signal that bridges the gap between "nothing" and the satellite downlink that we've been hard at work to deliver.

This beacon relies upon GNU Radio, a relatively inexpensive computer, a relatively inexpensive SDR, and some relatively expensive RF hardware from DB6NT.

This update is mainly about the transport stream, which has a lot to do with the formatting of how the data is delivered over the air.

The traditional DATV approach is to use MPEG as the transport stream. This is the traditional video stream, like in broadcast television. We specify GSE, or Generic Stream Encapsulation. This allows any packetized data. It reduces the overhead and allows for a lot more freedom. There are so many really fun things that we can do as hams here.

But we have to get from zero, to fun and accessible digital downlinks somehow. This beacon project is one of those steps along the way.

We start out with MPEG as the transport stream and show the transition from constant coding and modulation flowgraph to attempting a variable coding and modulation flowgraph.

A

Okay, here we are with the early prototype of the db s2 beacon in there at the bench in the remote lab, even though we're not remote this pc here this little, this pink one is a fairly powerful x86 machine and it's set up to run gnu radio companion and it's equipped with at the moment, blade rf, which is uh transmit and receive sdr with adequate bandwidth for our purposes.

A

The blade rf is hooked up to one of these antennas. The rest of these antennas are hooked up to various receivers.

A

One of them is the spectrum analyzer, which you can see, is showing nothing at the moment.

A

Another one is the receiver card, that's plugged into the pc called aperture, which is behind the bench, and this is its receiver it's frozen now, because there's no signal and the third receiver is running on this surface laptop and it is actually a mini tuner running the mini tune software and it's also showing no signal and just noise on the constellation diagram.

A

This screen up here is attached to the pink computer called hello kitty, and I can run mini radio companion.

A

It'll automatically load the flowgraph I was using last, which is the transm demonstration flow graph from guinea radio. With a few modifications, I've changed the program, material and swapped out the sdr sync for the one that drives the blade rf. So all I have to do now is click on start and this flow graph will start up and run and there's the uh the signal being generated, it's a little bit weak. So I'm going to turn it up here on the screen.

A

You can see there's a nice digital signal coming out from the spectrum analyzer and the mini tuner is automatically receiving it. This is live video being transmitted over this two inch path from between the antennas, the other tuner. I have to click on to make it receive again, but one two three boom there. It is, if you back up to see both screens, you can see they're both receiving the same program, so the the mini tuner has all sorts of instrumentation. You can see.

A

What's going on, you can see, it's got full smash, carrier, lock and symbol rate lock. It's showing rf power between about minus 38.

A

um Carrier uh carrier on noise message, error rate is here: we go yeah, I'm not sure what any r stands for in this context, but it's showing about 30 db and that's more than adequate. The this modulation takes about 14 db, so we're 15 db over that's what d15 means, so it's receiving excellent results.

A

This guy here has care quality indicators down here, so we've got l95. I think that means signal strength and quality. It's 98, so it's doing well as well. Of course, over these short pass. That's that's no surprise to cover a real path, we'll need a power, amplifier and filter antenna to make it work. Well,.

B

For the rf hardware, for the prototype, we have a transverter and a power amplifier automobile for scale.

B

This is the antenna that we're going to use for the prototype. This is by w6dfw silentkey. This is one of the last batches that he made and it's oh. So it is a slotted waveguide antenna and we will need an adapter to go to coax, and that is on the way we found a perfect inexpensive one on ebay.

B

Now we're going to show you a flow graph that doesn't work.

A

Notice this one has three different file sources, all feeding into this one giant, bb header block and then going through a very similar looking chain of modulation blocks. Actually, those are completely different blocks, they're enabled for variable coding and modulation.

A

So if I transfer begin this.

A

Game, that's all the game we're going to get out of that graph. Now this is a different symbol right, so I have to tell minnie tuner that my symbol rate is not 6 million symbols per second, it locks notice that it's showing a different constellation, but it's a little weird. It's showing count multiple different constellations at different signal strengths. That's because this is actually a multiple code rate transmission, but mini tuner is not smart enough to pick on just one of the code rate, so it's trying to modulate them all and mush them together.

A

The result is we get a little bit of trying to draw video, but it's never going to see the signal.

B

Well, it's one of the three programs. Well, it's the top.

A

Third of one of.

B

Those oh yeah, now.

A

B

Okay, we're on the right track.

A

B

Aps all right so we're doing another blind search on a vcm signal and every time we do a search, it finds something different.