GOES 16 GRB downlink vs GVAR

Discussion in 'Free To Air (FTA) Discussion' started by GOES 12 GVAR user, Sep 17, 2017.

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  1. GOES 12 GVAR user

    GOES 12 GVAR user Topic Starter SatelliteGuys Pro

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    He did some kind of fix, maybe to the web version as it mentioned some bug fixes.

    Looking good KWX. I see Florida and some of the Keys there
    I enhanced the image a bit
    Enhanced VIS.jpg
    Finally got my Sawbird+ from Nooelec.
    Sawbird+.jpg
    And one of the amps I ordered is in the states.
     
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  2. N6BY

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    They made two different versions and mine doesn't have the metal shielding or power connectors (just a circuit board). The only way to power mine is through the coax.
     
  3. GOES 12 GVAR user

    GOES 12 GVAR user Topic Starter SatelliteGuys Pro

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    This one looks like the SAW filter/LNA for the Outernet, Inmarsat model. All the amps I have coming have the connection from a power connector. I tend to stay away from the biased powered parts. I told them I wanted the Sawbird+ and that's what they sent.
    I'm still very impressed for what you get for 40.00 bucks.
    The cable run should be less then 1' long between the combiner and the Nooelec module, probably more around 6".
    Providing that it works as good as my DEMI amp, I will shield it and install it at the feed in an enclosure.
    If I need a 3rd module (amp) for sending the signal down the feed line I will have room in the enclosure for it as well. There will be 2 separate compartments for the 2 modules if needed. When I get to that point.
     
  4. KWX

    KWX SatelliteGuys Family

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    Nice, sure hope it exceeds expectations.
     
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  5. KWX

    KWX SatelliteGuys Family

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    An observations on the DD card.

    I noticed that from time to time (randomly), the GRBStreamer stops streaming as if the DD card lost "lock" on the signal, so either resetting the coax or hitting the stop button and start button once more a little while later, allows it to continue streaming. So... will be interesting to see if you guys get something similar or not if you're getting a DD card. I know Brett is getting one so let's see if he has a better or similar experience as compared to mine.

    So in a different topic, I'm wondering if I get a minicircuit ZAPD-2-21-3W+ (0 deg combiner) could allow me to get both LHCP/RHCP through one coax line. So here's the topology I'm chewing on:

    Canantenna -> Probe1 -> SMA 3-way splitter -> To Z10Q-2-25-S (LHCP) ...
    Canantenna -> Probe2 -> SMA 3-way splitter -> To Z10Q-2-25-S (RHCP) ... then combine the output of both Z10Q-2-25-S to -> ZAPD-2-21-3W+ -> LNA (outside) -> cable run -> LNA/Filters (inside) -> 3-way splitter -> Port 1 / Port 2 of DD (or dual port DVB2 card) for LHCP and RHCP.

    What you guys think?
     
    #285 KWX, Feb 11, 2018
    Last edited: Feb 11, 2018
  6. N6BY

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    I have seen that behavior with my TBS card. I got the DD card yesterday but am waiting for my MiniCircuits 90 degree combiner. Also am currently hit very hard by the flu. :sick

    I don't think it would work because you would have RHCP and LHCP on the same coax line at the same time, and there is no way to separate them after that. Once its in the coax, RHCP and LHCP are indistinguishable. They must be separated at the dish feed.

    One possibility might be to put 4 probes in your can antenna, all 90 degrees apart. Then use 2 90 degree combiners, 1 for each adjacent pair of probes. And 2 sawbirds. But you would need 2 coax lines.

    The only way to get around two coax lines is if you only had either RHCP or LHCP, but not both simultaneously.
     
  7. KWX

    KWX SatelliteGuys Family

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    Rest and hydrate a lot as you're likely doing, and I pray you get better sooner rather than later.

    Well, thanks for validating that nagging feeling that it wouldn't have worked with one coax. I've ordered one Sawbird to see how it performs which I should be getting early this week (knock on wood). It seems that by using the Sawbird that I would be replacing the LNA at the feed stage so it would do both, amplification and filtering. Unless I can use it after the LNA at the feed to further filter/amplify the signal, not sure if that's a possibility that you guys have tried so far.
     
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  8. GOES 12 GVAR user

    GOES 12 GVAR user Topic Starter SatelliteGuys Pro

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    Get better there Brett, the flu has been making the rounds.:(

    Don't know as I won't have any processing ability until maybe Wed. but weather is not very good now.

    KWX, first if you change the 2 probes around at the input of the combiner then you change the polarization.
    This is where Brett and me may be at disagreement.
    It's the phase offset the determines polarization of the feed so both coaxes have both polarization's present before it gets to the combiner.
    The septum feed does this in the waveguide via the polarizer (septum). Though we have not had much luck with that feed as of now.
    What Brett suggests is an idea that I have had as well,
    But this could cause a waveguide tuning problems with both probes sets at the same distance from the back of the waveguide. It "might" work if the probe sets for each polarization are at different distances from the back. But with any of this remember that you split the power you are receiving by 2 plus any losses.
    Example: RHCP is at a 1/2 wave from the back.
    LHCP is at a 1/4 wave from the back.
    So there's one suggestion,
    Here's the other:
    diagram dual combiner.jpg
    It uses 2 hybrid combiners and 2 splitters.
    The 2 combiners are switched in connections so that one output is LHCP and one is RHCP, requires 2 output coaxes.
    The idea is pretty much the same as yours KWX but there is nothing after the hybrid combiners but coax. Though you still do the same as you would a single line in terms of amps and filtering but for both. What you describe above would only need the 0 degree combiner to combine the 2 probes into 1 coax but....
    Summing this into one coax I don't think is possible.
    Maybe it's possible if your receiver can determine the two polarization's but not likely. The isolation isn't enough. As Brett stated above.
    The job of the combiners is to create isolation between the two polarization's while catching the circular polarization of interest.
    You would want the above diagram in a module such as the hybrid splitter, the use of strip lines and matching devices can make this possible and a very small block.
    In my opinion I would approach Minicurcuits with the idea and see if it's possible and if they can make it.
    As a block all one would need to do is hook up 4 coaxes and you're done.
    They might even already make it.
     
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  9. N6BY

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    Before they reach the combiner, yes, I agree that both coaxes have both polarizations present. But at any given time each coax line has a different signal. Once combined you cannot split them apart again.

    Its like adding two numbers, say 124 and 55. The result is 179. But information is lost in the addition -- you don't know which two numbers were added together to yield 179. In other words, you don't know how you got the 179, 100+79, 178+1, who knows?

    Once information is lost it cannot be recovered.
     
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  10. Titanium

    Titanium AI6US
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    Been following this thread and compliments to the progress on the project and the thinking outside the box!

    I do not understand the reason to combine the LH/RH polarities. Is the data duplicated and synchronously uplinked? Is the signal combining an attempt to increase the SNR or present additional data for the error correction?
     
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  11. N6BY

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    Thanks. NOAA transmits different data sets on the two polarities, at the same frequency. So the RHCP and LHCP signals contain different data and this is not an attempt to increase the SNR.

    In post #285, KWX was wondering if he could send both data sets down on one cable run to his house. I claim its impossible since they are at the same frequency. But GOES 12 GVAR USER thinks it would work. I don't think you can mix two different QPSK signals at the same frequency on the same cable at the same time, and then be able to split them apart and reconstruct the individual signals.

    What are your thoughts on this?
     
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  12. Titanium

    Titanium AI6US
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    Mixing two non-sychronized QPSK modulated sources on the same frequency into a single coax then running into a tuner, demodulating and attempting to process multiple tables and data streams will be equivalent to attempting to receive identical parameter transponders from two adjacent satellites. I agree with you that this will not work.
     
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  13. KWX

    KWX SatelliteGuys Family

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    Thanks for the great comments.
     
  14. KWX

    KWX SatelliteGuys Family

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    A little update on the DD card and the kind of odd behavior (at least for me) it gives me on randomly losing lock.

    I proceeded to test an AM filter, in an effort to filter outer as many signals as possible outside the GRB signal. Well, to my great pleasure, I've been able to have GRBStreamer run without losing lock for close to 24hrs now. Now, I still had to remove the coax and plug it back in so the DD would lock, like it has been reported before, but this time it locks on the first reconnect, so far so good.

    I'll be switching to the TBS 5925 and see how it behaves, as it too, would experience random loss of lock.

    Mileage will vary, from user to user, but wanted to mentioned it in the event it something clicks and other ideas come into mind.:)

    Due note that even though I'm testing the TBS, I actually like the DD as it has fewer sync errors with CADU/BB frames, as weather01089 mentioned.
     
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  15. N6BY

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    KWX, What distance are your probes from the back of the can? Are they both the same distance?

    Also, I'm surprised that the sawbird didn't filter out AM broadcast. But its great that you discovered that it helps. I've got an FM transmitter tower about 1.5 miles away and may need to do something similar.

    I'm going to try an experiment -- hook up the sawbird to my roof antennas and see how much broadcast AM/FM still gets through on my SDR.

    As for why we have to disconnect and reconnect the coax to get a lock, I am puzzled. I discovered something equally strange -- if I go outside and touch the sawbird which is encased in aluminum foil it helps it lock. Grounding issue?

    My Minicircuits 90 degree combiner arrived today. But I am still too sick from the flu to give it a try -- maybe tomorrow.
     
  16. KWX

    KWX SatelliteGuys Family

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    I haven't used the Sawbird yet, should be in the mailbox soon.

    Yeah sounds like a grounding issue, unless there's a loose connection (power or coax)!!!

    Very nice, looking forward to what you get, but health first so take it easy.
     
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  17. KWX

    KWX SatelliteGuys Family

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    In regards the distance, I built it 37.5 to 37.6 from the back of the can. There could had been some minor deviations.
     
  18. N6BY

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    You are doing well getting good reception without a sawbird.

    So both probes are the nearly the same distance from the back. Thats what I tried before I got my Minicircuits combiner.

    As soon as I can get a decent signal I plan to resume work on GRBStreamer. If it loses lock while streaming it needs to keep trying.
     
  19. GOES 12 GVAR user

    GOES 12 GVAR user Topic Starter SatelliteGuys Pro

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    I agree with you on that part, The disagreement I figured was about the phase of the signal determining polarization.
    I didn't explain that as good as I could have.:(
    If both polarization's are present at the receiver at the same amplitude on the same coax then I doubt they could be separated. I say doubt because if one has enough money a custom receiver can possibly be able to do it, but that is far beyond this discussion.
    Where I said that both RHCP/LHCP are present is before the hybrid combiner not after the combining and post processing.
    Sorry about the confusion. That maybe is a BIG maybe and again is far beyond this discussion.

    Hi Ti,
    NOAA had to make the best of the bandwidth they had to move all this data.
    They had about 12 MHz to work with so to transfer 17.33 MSPS they needed about 21 or so MHz of bandwidth for the selected modulation.
    It wasn't possible to get that amount of spectrum without major issues (Exp. since a portion of it had been auctioned off for broadband use and still needed to room for HRIT, exc.(remember the discussion on the EMWIN post)) so they took the GRB stream and split it between 2 circular polarization's with same data rates and in the same bandwidth.
    The above explanation is some research and theory.
    GRB product 2 streams of data...
    GRB Data streams.jpg

    This system was designed to work on 2 separate coaxes for each polarization. 1 coax to polarization.
    My diagram illustrates that the 2 probes may be able to get both streams for the 2 coaxes and receivers.
     
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  20. GOES 12 GVAR user

    GOES 12 GVAR user Topic Starter SatelliteGuys Pro

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    I can believe this, as we were talking about before that the waveguide does itself act a a filter for higher frequencies, it is not a fix all. If you have a very strong signal nearby then it's possible to cause issues. It works the same way as front end overload with the receiver.
    This it where shielding/grounding is very important, the strong presence of an RF field can get into the sensitive circuitry of the microwave blocks. Poor connectors, shielding and coax can be the culprit here. Amplifies up the strong signal (exp. theses broadband style amps) and the receiver has a hard time with it.

    I talked with guy on this forum that was trying to get EMWIN and he couldn't get any good data for any period of time. It was determined that a cell site camoed behind his house was the culprit of the desense of the receiver. Though he wasn't using any filters at the time before the receiver (SDR).

    Very well could be. I would be using alligator jumpers to help solve this issue. Also check you connections and coax for any issues.
    Use the ohm meter to determine if you have contact at all points..
     

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