GOES 16 GRB downlink vs GVAR

[N6BY]

After 580 posts and 6 months we have made a lot of progress! Here is a photo of my 10' Unimesh with a Septum feed aimed at GOES-EAST, currently receiving mass quantities of Earth and Solar imagery. It works and creates images, but gets bogged down after awhile. Now that I have a working hardware setup I can finally focus on the graphics software.

 

[N6BY]

Below is a Full Disc image I received from GOES-EAST today. The original is very detailed and over 100 megapixels.

I want to be able to create natural color images. In order to do that I have to receive and process both the RHCP and LHCP signals simultaneously because of the way NOAA split up the color channels. So today I ordered another Nooelec Sawbird+ which will let me hookup the other side of the septum feed.

 

[GOES 12 GVAR user]

The performance graph shown by Nooelec for their Sawbird+ (see attached) shows that its bandpass response is not suitable for GRB at 1686.6 MHz. An 80 MHz bandwidth centered on 1.542 GHz will result in very degraded performance at 1686.6 MHz no matter how good its noise figure is. You said that it is "specially designed for GOES GRB reception. Apparently I am not looking at the right version of the Sawbird+ ? I do not see a version that is specially designed for GOES GRB at 1686.6 MHz. What am I doing wrong...??

Mike, see the performance graph I posted of the sawbird+
Sawbird+ plot
Here is a picture of the sawbird+
Post 281
Yes it does work and at a very reasonable price.
It's a bit confusing as they don't list the Sawbid+ on the web page. Only show the other model that works below GOES.

Mike, I don't know if you did check your conversations under your profile page.
But I did leave you info on NOAAPORT there.

Great Job Brett, You have earned it. Looks good.
Now my turn....

 

[N6BY]

...
Great Job Brett, You have earned it. Looks good.
Now my turn....

Thanks.

Your TBS5927 is scheduled for delivery to me later today and I'll test it under on Windows 7, 10, and both feeds. We'll get yours working soon.

Meanwhile, here's a sun image I got today showing some surface activity.

 

[Micanopy Mike]

Good news. I just finished testing the septum feed with GOES-17 at 89.5W. I got an SNR of 10.0 !! Thats about 2 dB better than the cookie can's 8.0.

So tonight I'm going to re-aim my dish to GOES-16 75W and try processing it.....

View attachment 132971

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Hi, Is your septum feed homebrew or commercially made (i.e. RF HamDesign ?) Have you characterized it for LH vs RH polarization isolation? If it is from RF HamDesign, their L-Band septum feed is spec'd for use with 0.40 to 0.45 f/D dishes. Was your received GOES-W SNR of 10.0 dB done with your 10-ft dish? If so, what f/D does your dish have? At this point I only have an 8-ft dish as my Wineguard 12-ft dish got destroyed by a falling tree during Hurricane Irma. I am still looking (unsuccessfully) for a suitable 12-ft dish to replace it with.
Thanks for your feedback on my questions! -- Mike Baker
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[Micanopy Mike]

Mike, see the performance graph I posted of the sawbird+
Sawbird+ plot
Here is a picture of the sawbird+
Post 281
Yes it does work and at a very reasonable price.
It's a bit confusing as they don't list the Sawbid+ on the web page. Only show the other model that works below GOES.

Mike, I don't know if you did check your conversations under your profile page.
But I did leave you info on NOAAPORT there.
**********************************************

I did not realize that some posts showed up in different places on this forum. I have participated in a "chat-list" for some years where every post is always seen in every members email IN-Box. However, i have never used a "forum" like this before and I still have not figured out how to use it. I have not seen any set of instructions for this forum for newbies like me. Thanks for your patience with me !! Mike Baker

 

[Titanium]

Interesting article on budget reception LRIT/HRIT. Seem quite underwhelming compared to your projects!

Building A Low Cost GOES Weather Satellite Receiver with an RTL-SDR - rtl-sdr.com
A minimal LRIT/HRIT receiver — goestools documentation

 

[N6BY]

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Hi, Is your septum feed homebrew or commercially made (i.e. RF HamDesign ?) Have you characterized it for LH vs RH polarization isolation? If it is from RF HamDesign, their L-Band septum feed is spec'd for use with 0.40 to 0.45 f/D dishes. Was your received GOES-W SNR of 10.0 dB done with your 10-ft dish? If so, what f/D does your dish have? At this point I only have an 8-ft dish as my Wineguard 12-ft dish got destroyed by a falling tree during Hurricane Irma. I am still looking (unsuccessfully) for a suitable 12-ft dish to replace it with.
Thanks for your feedback on my questions! -- Mike Baker
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Homebrew. I'll publish the septum dimensions here tomorrow.

It works for receiving both RH and LH simultaneously or either one independently. I don't know what the cross polarity isolation is because I lack the necessary equipment. But apparently the isolation is good enough.

I have the 10 ft Unimesh dish as shown in post #581, which has an f/D of 0.40.

Since I can receive GOES-EAST easily from California on a 10 ft, I think your 8 ft will do fine since you are closer and the dish elevation angle will be higher.

Magic Static' offered to give his 12 foot dish away earlier, but that's a long drive! TEK 2000 sells them, but based on what I read they are of poor quality.

 

[N6BY]

Tim sent me his TBS5927 and I received it today. While it will lock the GRB signal without trouble, it does not create a usable stream. I tried it with both the Windows 7 and 10 drivers.

So currently the known working receivers are the TBS6983, TBS6903, Digital Devices Cine V7A, and the TBS5925 that 'KWX' is using.

But the Digital Devices Cine V7A is very limited in capability as a general purpose receiver. It does not have blind scan and software support is limited. They have not responded to 'weather01089's request for a Windows software development kit (SDK).

The TBS6983 and TBS5925 are discontinued, so the TBS6903 would be my first choice.

 

[GOES 12 GVAR user]

I did not realize that some posts showed up in different places on this forum. I have participated in a "chat-list" for some years where every post is always seen in every members email IN-Box. However, i have never used a "forum" like this before and I still have not figured out how to use it. I have not seen any set of instructions for this forum for newbies like me. Thanks for your patience with me !! Mike Baker

I understand that, yes there is little info on all the functions of this forum
Here is some guidance of basic functions:
Link to page
How to access the conversations page:
Click on your profile page at the top of the browser
When the dropdown box appears click on conversations. ( red box)

This is your inbox on here. It's where you can have personal conversations with other members.
The NOAAPORT conversation is not (on topic) of these posts and gets off subject.
These posts here are for GRB and GVAR primary so that the forum keeps on the subject at hand.
With the conversations page I can talk about something else with you while not ting up the forum here.
If we so decide we can even start a new forum of NOAAPORT as there are many users on that have it, but not on this discussion here
Once on the conversations page look for the conversation you want to view

Click on it to open it and respond to it as you would on the forum.
Hope that helps a bit.

Have you characterized it for LH vs RH polarization isolation?

The septum feed should have about 20dB isolation between polarization's according to Paul Wade (W1GHZ)

Mike, I think as Brett said you should be able to get that on an 8' dish there. If you have 10' then you will have even more S/N margin.
12' would be overkill for Fl, but if you have it use it.

 

[GOES 12 GVAR user]

TEK 2000 sells them, but based on what I read they are of poor quality.

The polar mounts on those are junk, the dish looks good though. Wayy overpriced.
If you endup getting one be ready to rebuild the polar mount as the one that it comes with is likely to fail in any sig wind event.
Thanks again Brett.
I figured that it was the receiver. I saw also the slow output but I wasn't sure if that was normal. Showing me the side by side comparison makes a huge difference.
The TBS5927 is Generic deaf.
I am still waiting on Omnicom, as it still may have some hope.

 

[N6BY]

I posted the dimensions and construction details of my GRB Septum. Its here: Experimenting with L-Band antennas

I may try design variations in the future. I would especially like to make it lightweight, using thin metal sheeting with 90 degree bends.

 

[Micanopy Mike]

I posted the dimensions and construction details of my GRB Septum. Its here: Experimenting with L-Band antennas

I may try design variations in the future. I would especially like to make it lightweight, using thin metal sheeting with 90 degree bends.

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Hi-- Have you characterized your home-brew GRB septum feed with a vector network analyzer across a swept frequency spread of---say...: 1650 to 1750 MHz ? If so, can you provide a copy of the display screen capture of the Smith Chart and SWR ?

I have never built a septum feed but I have constructed a number of assorted feeds for Met-Sat birds and learned early on that tweaking dimensions of any type of feed for best performance without some means of measuring capacitive reactance, inductive reactance plus circular polarity isolation and 50 ohm matching across the frequency range of interest is critical. Minor dimensional changes often may improve one characteristic and degrade one or more others. Without some means of seeing all of the needed performance characteristics collectively it is like trying to hit a small target with an arrow while wearing a blindfold. Used, but good working HP VNAs are not inexpensive but either owning one or having access to one is essential to preserving your sanity when constructing or evaluating feeds for antennas. I acquired a used but good working HP 8714 ES a couple of years ago and it made a **HUGE** difference in preserving my sanity when constructing or characterizing any kind of antenna or feed performance. Again, if you send me a feed to characterize I will return it and a hard copy of the tested parameters from the screen capture.

Mike Baker

 

[N6BY]

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Hi-- Have you characterized your home-brew GRB septum feed with a vector network analyzer across a swept frequency spread of---say...: 1650 to 1750 MHz ? If so, can you provide a copy of the display screen capture of the Smith Chart and SWR ? ...

I don't have a vector network analyzer. But I do have EBSPro Mobile on Android to measure the SNR while out a the dish. I can tweak the dish aim and the feed distance from the dish, and the mobile app audibly calls out the SNR. Or I can view the spectrum with my SDRs. Here is a screen shot of about 50 MHz of GOES-EAST RHCP. At 1686.6 it is about 10 dB above the noise floor. While I have no way to measure the cross polarity isolation, I know it is good enough because I can receive RHCP and LHCP without errors.

...
I have never built a septum feed but I have constructed a number of assorted feeds for Met-Sat birds and learned early on that tweaking dimensions of any type of feed for best performance without some means of measuring capacitive reactance, inductive reactance plus circular polarity isolation and 50 ohm matching across the frequency range of interest is critical. Minor dimensional changes often may improve one characteristic and degrade one or more others. Without some means of seeing all of the needed performance characteristics collectively it is like trying to hit a small target with an arrow while wearing a blindfold. ...

I agree completely. When you have a dish feed that doesn't work, and you don't know why, you can only make educated guesses and make changes through trial and error. Even more frustrating is when you have a working feed and don't know it. I built the septum in December and thought it didn't work. But in retrospect the problem was either my LNA / Saw Filter or the way I was powering it.

...Used, but good working HP VNAs are not inexpensive but either owning one or having access to one is essential to preserving your sanity when constructing or evaluating feeds for antennas. I acquired a used but good working HP 8714 ES a couple of years ago and it made a **HUGE** difference in preserving my sanity when constructing or characterizing any kind of antenna or feed performance. Again, if you send me a feed to characterize I will return it and a hard copy of the tested parameters from the screen capture....

Thanks for the offer, but I am afraid to part with it (even for a short time). I am now working on fixing the data ingestion and image processing software. Also, I am currently participating in NOAA's GOES-17 test program and providing them signal reports and data quality verification.

 

[N6BY]

Another one of the sun. My next image will be a natural color earth shot. Maybe next week....

 

[Micanopy Mike]

Hi--

You said: 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.
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I have never seen a helical inside any kind of waveguide but always mounted on a flat plate. The illumination angle of even a 3 or 4 turn helix is quite narrow and placing it in a can or waveguide even further restricts the illumination angle. Paul Wade, W1GHZ has written this up in his book chapter on helicals. I built some experimental helix feeds a couple of years ago and a couple of photos of one of them and its matching adjustment are attached.

What commercial sources do you know of that are selling 10', 12' (and larger) C-Band dishes other than the one in Ontario, Canada ?

Mike Baker
Micanopy, FL

 

[N6BY]

Hi--

You said: 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. ...

That was way back on October 28, 2017. But I never got around to trying it.

 

[GOES 12 GVAR user]

Mike, lets us know how the helical works out for you.

What commercial sources do you know of that are selling 10', 12' (and larger) C-Band dishes other than the one in Ontario, Canada ?

Not too many any more that I'm aware of. Most C-band dishes are come by the used market. I have only bought 1 new dish since I have been doing this, otherwise all others are used.
I know that Andrew the same Mfgr that makes the Heliax made satellite dishes, but I bet you don't want to know what they cost.
I recommend that you check the used market, local or online for a used C-band dish. 10' and smaller can still be had out there.

 

[Magic Static]

Yep still out there. I know where a pile of them are.

 

[Micanopy Mike]

RE: Searching for a 12-ft or larger dish

Yep still out there. I know where a pile of them are.
View attachment 133142 View attachment 133143

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I have been searching for a used 12-ft dish for some months but with no luck. For my GOES-East GRB downlinking project I have found a number of abandoned 10-ft dishes but all were in pretty bad condition so I am currently stuck with an 8-ft dish. As of now I have found no leads on a used 12-ft (or larger) dish that is in very good shape. My own 12-ft aluminum dish got crushed when a big tree fell on it thanks to Hurricane Irma. I will drive to pick up a 12-ft or larger dish that is within 500 miles or so. For a really good deal on a good 15-ft dish I could use for EME on 2304 MHz I would make a several day trip to pick it up and bring home. Any leads or contacts for locating and retrieving a good condition 12-ft or larger dish within a 1-day drive from my North Central Florida home in Micanopy, FL will be very much appreciated!! Mike Baker