GOES 16 GRB downlink vs GVAR

[GOES 12 GVAR user]

Hwboy4,and all others reading this..
I want to make it clear that I support Lucas Teske and the open satellite project. I tip my cap to him and the others that take hours to write all the code that goes into this stuff .
I am more then happy to provide this info as I have been in this position myself trying for find data on a subject.
To add to that, this is what makes it work, hobbyist and pros working together to make a product more accessible.
There are 2 big costs$$ to weather satellite data.
1. Physical hardware to capture the radio signals
2. Software, This one is more than hardware at times.
With the data becoming all digital the latter is a must to have.
As stated in post #1 hardware costs are coming down but software is still expensive. Commercial software for this could run into the 1000s of dollars and very well 10s,000s.
So the people like Lucas and the others out there doing this should be treated very well.
Most don't realize the lines and lines and lines X 1000s of code and time X days to make a computer ingest this stuff.
Computer code is not my fortae.
From what I see on the SDR the GRB signal is as strong as GVAR here and I get GVAR with 2 to 3 dB margin.
If I fall short it won't be by much and my 12' dish should make up for it.
A standard DVB-S2 board or IP output DVB-S2 receiver should be able to decode the outer layer of the signal.
Before NOAAPORT went to S2 I used a off the shelf PCI DVB card to decode it.
The receiver I will use is the NOVRA S300D.
The cheaper ones on ebay may work as long as it does IP data and has a reasonable S/N. Not shure how well the cheaper ones do.
The combiner should be here today so I'll I need to do is get the cables made up.
I have been holding out on this part until I got to this stage but I think it's time to put it out there.
As I stated in post #1 that the software is available for download so..
The Space Science & Engineering Center out of the University of Wisconsin -Madision has made the software for ingesting GRB and can be found here:
Community Satellite Processing Package for Geostationary Data
Not only will it ingest GRB it can do GVAR as well.
They also make a test package for the GRB data to use for checking the operation of the ingestor.
It's written for Linux Sp. 64 bit CentOS
Mabie Lucas and his fellow software developers of open satellite project may be able to use this, pass it along.
It's fully functional software.

 

[hwboy4]

Great stuff, thanks. I registered at RocketChat and searched the OpenSatellite project for the DVB-S2 firmware without finding it. I'm curious which receiver and PC board is the firmware designed for? i have a TBS6983 board, and a few stand-alone DVB-S2 receivers.

... Also, some connectors that I need to test my patch antenna on my satellite dish are supposed to arrive today. Will see how strong the signal is from 89.5W.

Ask Lucas (racerxdl) which DVB-S2 board is being tested. The beta firmware is for an Ayecka receiver which is a standalone device but costs quite a bit more than the PC board alternative.

 

[N6BY]

I finally got the connectors that I needed to test my patch antenna on the 8 foot dish with GOES-16. So I moved my dish over to 89.5W, mounted the patch antenna at the feed point, and fired up my SDRPlay.

I saw absolutely no signal whatsoever from 89.5W at 1686.6 MHz. As a reality check I moved the dish to Intelsat at 98W and saw numerous L-Band signals in the SDR waterfall, including Outernet.

I double checked my aim at 89.5W with a KU band LNB and was able to receive the numerous church channels from the nearby 89W bird.

So.... I know the dish is aimed properly. But the patch antenna is designed for 1539 MHz, not 1686. That may be part of the problem. Also, I was using a long cable run and no LNA.

I think my next step will be to make a 3-turn helical coil tuned for 1686 and place it in a metal can wave guide. Will add an LNA at the dish too, to help offset the loss from the long cable run.

Any other ideas are most welcome.

Also, I found out that those specialty generic stream DVB-S2 receivers are very expen$ive!

 

[GOES 12 GVAR user]

LNA a MUST.
Remember how weak the signal is coming out of the waveguide in my post on a 10' dish, Your signal is 6 dB down from mine at least due to the antenna size, use the LNA.
N6BY what does the noise floor show for a level of SDR Play? I assume that it does have the scale such as HDSDR.
I'm curious to know. Have the dish aimed near where you want it with just the noise look at the noise floor on the scale.
I got my combiner and just finished the cables with getting it all hooked up. Mabie I will go out today a run another test....mabie.

 

[N6BY]

...
N6BY what does the noise floor show for a level of SDR Play?
...

The noise floor was -94dB, but that varies depending on the SDRPlay gain setting. I used my own SDR program for the test (DR Processor from n6by.com ).

Will try the LNA next week. I need to order some more connectors to hook it up.

 

[GOES 12 GVAR user]

N6BY,
Might want to keep that gain setting near midrange or as low as possible. Just a suggestion.
Also I would try to use the HRIT signal at 1694.1 for peaking the dish as the GRB signal looks more like noise. The HRIT signal also has audible tones with the headers being sent.
Got out I did some more tests today. The result was great. The first picture is the GRB on HDSDR with the RHCP feed. The result is better then the first as expected.

The signal level the first time was -114.5 dBm or near that, after the RHCP feed it's up to -111.2 dBm. This is a 3.3 dB increase in signal level.

I didn't measure the noise floor but would expect that it didn't change much with the feed polarization, though I do want to get a measurement of it, ran out of time.
Signal level should be near 16.8 dB above noise.
I did this earlier before I got the HDSDR info (if you look at the computer's clock)
Hooked up the DVB-S2 receiver and have lock.

Some interesting items note though, The signal level is below the threshold of what the receiver expects so there is no signal strength indicator bar.
But the receiver is locked, I confirmed this by several ways.
1. Checked the manual and checked again.
It states by the green lights:

* Status – Turns green when the status packets are being successfully received from the S300 by the S300 console.
* Signal – Turns green when the receiver detects an input RF signal at the selected frequency. This matches Signal LED on the front of unit.
* Data – Turns green when the S300 has achieved data lock. This means that the receiver is able to recover all the digital timing from the input signal and is receiving a valid DVB transport stream.

Seems good there,

2. Checked by: Moving the dish from the satellite slowly and watching the packet error rate increase as the signal dropped down to 6.5 dB above C/N also saw the (DVB packets with Bad sync) rapidly increase.
Seems good there too,

3. Confirmed by: MODCOD 9/10 QPSK is what manual states it should be and the carrier is 1686.59 Mhz.

Yep, that's a match.
So I have signal lock with a 10' dish is SW Iowa on GOES 16 GRB RHCP.
C/N peaked around 9.1 dB and has about 2 dB margin, at least 1.5 dB min.

The only thing that bothers me is (and determined later) is the...
DVB Packets Accepted
and
DVB Packets In The Clear
numbers are not scrolling upward.

Later determined to be a IP data content issue as there must be some PID's that the GRB stream has that I didn't see in the manual, Have to look again.Otherwise I will have to contact NOAA for the info.
The same happens on NOAAPORT if the PID's are not set correctly.
The next things l'll be doing some changes to the block layout and add a bandpass filter to the system.
The ingest system is down the road as it's a whole another issue and cost.

 

[GOES 12 GVAR user]

Little more info to add to above. The Symbol rate is exactly as the manual states 8.665938 million symbols per sec. Per QPSK 9/10 FEC.

Also looking at the manual does show the APID's in appendix A, page 314 of the PUG (see post #2 for that manual) There's a lot of APID's.
Once the APID's are entered it's down the network cable to the ingestor to begin putting the space packets back together and make data files in the computer.

So a 10'dish will do the job for GRB on one data stream (polarization) in the Central US.

I not only want to change some of the blocks of the system but also want to try cheaper DVB-S2 receiver. It's not required to use the Novra receiver for this but it's what I had. And yep, those receivers are a bit expensive but I think you get what you pay for when it comes to them.
The receivers I choose to use are stand alone, this makes them compatible with many OS's. All that's needed is the way to configure it as well as the ethernet jack.
I wish GVAR was as simple as this.

 

[GOES 12 GVAR user]

I ordered a cheap china box (DVB). Have to see if it can do the job when it gets here. Currently shipping.

 

[N6BY]

I'm curious, which receiver did you order?

 

[GOES 12 GVAR user]

My cheap China box is a Freesat V8 Super DVB-S2 receiver. They're are over Ebay.
According to the the specs it has a little better sensitivity then my Novra S300.
Since it's (supposed) to adhere it DVB standards it should be able to do the job. (should Hi Hi)
The cost is cheap so I figured I'd give it a try.
I saw on youtube a video demo of the menu on it and found two major items that made my decision.
1. It has networking capabilities and
2. You can add you own satellites and transponders.
And if it don't work I can use it to level a piece of furniture...Like a workbench.
My next choice would be around $160 cost. But since I had the manual sent to me I understand less about it then what I got off Ebay. Hence the cheap China box decision.
N6BY,
How are your trials coming there? Any progress?

 

[N6BY]

...
N6BY,
How are your trials coming there? Any progress?

I've been away on vacation since Saturday, so no progress to report. I hope to try hooking up the LNA tomorrow (Wednesday).

... I'll be pleasantly surprised if the low cost receiver can pass a generic DVB-S2 stream over the internet. I have a U4 Quad DVB-S2 box which reportedly has the 'TVheadend' server built-in. If I can get a strong enough signal for GRB, I will give it a try.

I also have a 10' Unimesh dish which is currently sitting idle (not mounted on a pole). Its an option if the 8.5' Birdview fails.

 

[N6BY]

I installed the LNA tonight. It came with no documentation. I wasn't sure if it could get its 5 volts through the RF cable.

Tried it with my AirSpy (Bias Tee power set to 'on') and it didn't work. So now I will have to run a separate set of power wires to the LNA. Will try again when that is setup.

 

[GOES 12 GVAR user]

I''ll find out if that China box works.

I have a U4 Quad DVB-S2 box which reportedly has the 'TVheadend' server built-in

From the specs I found that has the max speed of 15 Mb/s. A single GRB stream will be at or over that spec. But it should still lock on to the signal and give you the C/N.
You should be able to see HRIT with birdview as that dish is more then adequate for that signal.
Be waiting to hear the news.
Yep, some LNA's are biased through the coax and some require a separate power to use them, some can do bolth.
My Ultra LNA is powered with a 12-15V DC supply separate power supply. (wall wart)

 

[N6BY]

I...
You should be able to see HRIT with birdview as that dish is more then adequate for that signal.
Be waiting to hear the news....

I just checked (without the LNA) and get nothing at 1694.1 MHz (HRIT). But it uses linear polarization and I have an LHCP feed. However, I do get a narrow band signal at 1680 MHz, whatever that is.

 

[GOES 12 GVAR user]

I do get a narrow band signal at 1680 MHz, whatever that is.

The signal you see is DCS (DCPR) 1679.9 Mhz. Since you see something of this you should be able to see other signals as well even with the circular polarization.
To get more info on other signals goto GOES Rebroadcast (GRB) Downlink Specifications, page 6.
See below image of other L band downlinks.

 

[Titanium]

Remember that reception of circular with a linear probe or visa versa will result in an approximate 3dB loss. If the target transponder is near the threshold, this loss will attenuate it into the noise.

 

[N6BY]

Remember that reception of circular with a linear probe or visa versa will result in an approximate 3dB loss. If the target transponder is near the threshold, this loss will attenuate it into the noise.

According to the docs, DCS at 1679.9 is RHCP. The combination of my Outernet patch and the reflection off the dish makes my receiving system LHCP. So I'm very surprised that I'm seeing DCS and nothing else?

I will try RHCP and see what I get. Also I still need to find a way to get power to the LNA.

 

[N6BY]

I changed to RHCP and added a powered LNA at the dish. Now DCS at 1679.9 is just a very faint trace. No signal visible at all from GRB at 1686. Maybe they turn it off at night?

Next I think I'm going to try making a linear feed in a metal can waveguide.

 

[GOES 12 GVAR user]

Agreed Ti,
But..the dish that N6BY is using is at least twice the size needed for HRIT so even though he looses 3dB due to polarization mismatch he should see HRIT, DCS, TLM signal come above the noise. Unless the noise floor is that high.
I would expect that his signals should be no less then 1/2 of what the my spectrum pics show. N6BY is seeing the DCP signal at 1680 Mhz.
I used my RHCP horn and could see HRIT (though weaker than the first time) I could still see it.
As mentioned before HRIT requires a 4' dish or less from what I know.
N6BY, you did mention earlier that patch antenna may not want to work up in this frequency range. Since you only see the DCS signal my thought is that may be the case.
With out being at the site it's hard to pinpont any one issue.
They don't turn off GRB at night.
Keep digging you'll get to the bottom of the issue.

 

[N6BY]

I just finished some more testing. I am now confident that whatever I am seeing at 1680.0 MHz is not DCS.

Its at exactly 1680.0, not 1679.9. It is much narrower than the one shown in post #35 above. The 'signal' is present no matter where I move my dish. And I see a similar signal at 1780 MHz.

As a reality check, I moved my dish over to 98W and saw the Outernet signal.

At 121W longitude, I am probably outside of the range of GOES-16, especially with an 8.5' dish and a circular patch antenna tuned for a lower frequency.