GOES 16 GRB downlink vs GVAR

That's some great news!!!

 

Hopefully I'll get some additional time this week to work some more on the LINUX app that I used to get the signal status and add streaming capabilities to send BB Frames to CSPP. Likely ensuring the BBF are synced before re-transmission will be the challenge for me. lol

 

weather01089 received a reply from Digital Devices last week. They told us that the DD card switches AGC (automatic gain) modes after a cable pull.

There are 2 gain modes, NF and IIP3. After pulling the cable and reconnecting, the card goes into NF mode which is when streaming starts.

They added a Windows registry key which is supposed to allow us to force the card into NF mode. But weather01089 tried it and it didn't help.

My best guess is that streamreader.dll is somehow overriding the Windows registry setting. CrazyCat (author of streamreader) claims it doesn't, but I have doubts. So I am currently in the process of writing my own code to eliminate the need for streamreader.

 

EBS Pro can record from most DVB cards (and it is currently 'freeware'). Since it uses streamreader.dll you need to edit the streamreader.ini file and uncomment the line "NoPidFilter=1". Another possibility is TSReader, but the free version doesn't allow recording.

And there are other programs you might want to try, like 'ProgDVB', 'SmartDVB' and 'DVB Dream'.

Anyway, if you can get a recording from the card I can analyze it and see if it looks like it has valid BB Frames.

 

That is a good question. I don't know what will happen with the Omicom card. My TBS6983 card with GRBStreamer automatically selects TS or GS depending on the MAType-1 byte (the first byte of the BB Header). The Digital Devices Cine V7A also looks at the MAType-1 byte, but if it detects BB Frames it encloses them in a series of 188 byte TS packets.

But I have never tried an Omicom card. Be sure to uncomment the line "NoPidFilter=1" in the streamreader.ini file. And then reboot your system to ensure that the change takes effect.

If EBSPro gets confused by the GS stream then let me know and I will send you a version of GRBStreamer that records to a file.

 

I have been following the GOES GRB thread with great interest as I am interested in downlinking and displaying the near real-time animated GRB imagery. I noted the comment about being interested in downlinking the GOES West GVAR imagery. I happen to
have a GVAR modem and a companion bit-stream synchronizer that was used for downlinking GOES-East GVAR a few years ago.
I am guessing that they are suitable for the current GOES-West GVAR signal. Both of these items and their manuals are available
if there is any interest in them. They have been sitting on a shelf in my workshop building for some years but were both functional when they were taken out of service. I am located in Micanopy, FL just 8 miles south of Gainesville, FL.

As a side note, I am a rank-newbie at using forums like this one and totally unfamiliar with how to make them work. It took me a while to find out where to click to post a response to this long-running GRB / GVAR thread. I am currently working on RX and display of the GOES-East EMWIN imagery and have what I think is a pretty good signal level from my dish. The GRB signal also looks pretty strong as well but this photo is from a linear polarity feed and the CP GRB signal is reduced by several dB. I am not sure if it is good enough to actually use at this low signal level. I'll try to post a photo from my spectrum analyzer of the signals but am not sure how to do that. I see a place to click on to "Upload a File". Is this where/how I post a photo to this thread? What are the file size requirements for posting my .jpg photos? I will take a chance and try to post something that is pretty low-res. The LHCP feed is a homebrew version. I used a CP patch feed and attached a 0.4 dB NF / 20 dB gain LNA followed by a 2 dB NF / 30 dB gain amp to send the signal thru the 100-ft of 1/2" Andrews Heliax hardline coax into my workshop. The GOES signal photo is from a Tektronix spectrum analyzer inside my shop building. I hope these photos are a suitable file size for uploading onto this forum!

 

Welcome to the discussion.

The GRB signal looks good as displayed in your photo. But unfortunately NOAA decided to include both polarities (LHCP and RHCP) at the same frequency. So with your linear polarity feed you're getting a mixture of both signals, and it would be impossible to process. A RHCP or LHCP circular polarity feed with good cross-polarity isolation is required for receiving GRB

The information content is different on the two polarities. A list of the contents of each polarity is below. It's from the GOES GRB Product Users Guide.

 

Hello, N6BY--

It is Brett, isn't it? I think that is what I saw on the FCC license listing. I have been
WA4HFR since around 1963. Some background on me; I built a GOES-East GVAR
station for the U of Fl Climatology Research Department in 1981. The Climatology
Department had a NASA contract to improve the freeze forecasting algorithms
for the cold-sensitive agricultural interests of the state of Florida. Back then
GOES products and imagery were not available on the Internet and the only way
to acquire them in real time required a direct down-link.

There was a huge clamor by local hams to receive the animated CONUS and
Florida image sector. I (illegally) installed a 70-ft tower on top of my 4-floor office
building and put an 18-ft tall stacked co-linear 13 dB gain omni-directional
Super Stationmaster antenna on the tower. My office was on the 4th floor
directly under the tower and I ran a 100-ft length of 1-inch Andrews Heliax
hard-line coax down from the antenna and connected it to an amp from a
defunct low-power TV station. The amp used a single Eimac 8877 (3CX1500)
tube running full-legal power NTSC video on the ham 426.25 70cm band.
With NTSC video, maximum average power applied to the antenna system
is 57% of the peak sync tip power, even in a black scene. In normal program
content this ratio may be around 25% or less. The nature of the GOES GVAR
imagery was such that with such an effective antenna system the TX met
all power restrictions.

Clear video was easily received out to around a 25-28 mile radius from my
office. This system ran 24/7/365 as a "beacon" for almost 10 years. Eventually,
the GOES imagery became available on the Internet and the transmitter
system was shut down.

The RX consisted of an 16-ft dish feeding a de-mod box and a bit-stream
synchronizer followed by some TTL hardware to decode the incoming data
and then into an Amiga 2000 desktop computer to turn the data into
image pixels and scan lines and then convert this into NTSC video.

I had some experience with video as I had been chief-engineer for the
U of F TV station WUFT-TV5 for several years. Interestingly, here in Florida
hams use the 70 cm band on a secondary basis with the military as there
is a bombing range not far from us near the Ocala National Forest and
hams are limited to 50 watts TX power. A friend of mine was in charge
of communications for the military in this region and I appealed to him
for a power waiver. After about a month I received a document permitting
me to run full legal power if I changed my originally selected frequency to
426.25 MHz as the military was not using anything close to that exact
frequency. I framed that letter and hung it on the rack holding the TX.
The Eimac 8877 tube was capable of loafing along running 1500 watts
peak video sync-tip power. The 8877 tubes were expensive and started to
get soft after around 8K or 9K hours. Every year or so the 40 or 50 area hams
watching the GOES GVAR video took up a collection for a new tube.

Eventually, the GOES GVAR downlink was shut down when the NASA
development contract ended and the GVAR system was declared
surplus, dismantled and declared available for salvage. Unfortunately,
the dish was acquired by another U of F department. I saved the
GVAR modem and bit-sync and took my tower and antenna home.
It was a fun side-line project while it lasted!
**************
My current interests are: A) Downlinking the new GOES-East EMWIN
signal and eventually; B) Downlinking the GOES East GRB signal. I am
primarily interested in the animated Geo-Color imagery. However,
it is not clear to me if this product is contained in just one circular
polarity signal or if it requires processing both circular polarity
signals to produce. Any info on this will be much appreciated!!
*************

One last item: You said--
> A patch antenna may not work for this as it don't have the best match
for a dish. You can try it, let us know.
*******

Hmmmm.... CP Patch feeds are commonly used on commercial
V-sat off-set (and some prime-focus) dishes. I do get more GRB
signal with the CP patch than with the linear polarity feed but I will
have to take another look at it and let you know what I see.
*********

Yikes-- I see that I have gotten carried away with far too long of a
text post. I tend to do that... My apologies!

Mike Baker
*********