Goestools shows 12 or 13 drops after five lines with zero drops, vit is under 400

[Richard Ingram]

I am using the standard wifi grid dish with Sawbird LNA + Smartee XTR sdr + RPI 3B.  Got it lined up on GOES 16 which is at AZ 160 , EL 50 here in central Alabama. I have the vit running below 400.  When I first start goesrecv (see screen capture below) I get about five readings with zero drops and then it immediately jumps to 12 or 13 and never changes. goesproc never writes an image file.  I have reinstalled Raspian Lite on a new sd card and setup goestools with no problems and both sdcard s produce the same 12 drops. the sample rate is 2000000 and gain is 8.

[Don Wade]

Hi Richard 

I’m just starting to get into this area.

Can you tell me what “wifi grid dish” you are using and where do I get one?

On May 26, 2022, at 9:18 AM, Richard Ingram <ringr...@gmail.com> wrote:



I am using the standard wifi grid dish with Sawbird LNA + Smartee XTR sdr + RPI 3B.  Got it lined up on GOES 16 which is at AZ 160 , EL 50 here in central Alabama. I have the vit running below 400.  When I first start goesrecv (see screen capture below) I get about five readings with zero drops and then it immediately jumps to 12 or 13 and never changes. goesproc never writes an image file.  I have reinstalled Raspian Lite on a new sd card and setup goestools with no problems and both sdcard s produce the same 12 drops. the sample rate is 2000000 and gain is 8.

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[Richard Ingram]

I got the Nooelec Bundle from Amazon.  It included the dish, sawbird lna and smartee xtr sdr.   I was hoping someone might have some insight on my problem.  I thought that the vit below 400 and low rs indicated a signal good enough to decode.  I'm at a loss for ideas.

Richard

[Carl Reinemann]

Richard, 
Can you post the contents of your goesrecv.conf file?  400 viterbi is just the bare minimum in my opinion, for a 'good' signal. I would strive to get at least 250. But let's see the goesrecv.conf file first.

Carl

usradioguy.com

[richard ingram]

Carl

Thanks for the reply. I'm new here so hope this is proper way to respond. My config file is one that was listed in the instructions I used. I have had vit in the 300 range at times, but what puzzles me is the results are always identical.  I get 4 or 5 lines of zero drops then jumps to 12 drops and stays there. 

goesrecv.conf

[demodulator]
mode = "hrit"
source = "rtlsdr"

[rtlsdr]
frequency = 1694100000
sample_rate = 2400000
gain = 45
bias_tee = false

[costas]
max_deviation = 200e3

[decoder.packet_publisher]
bind = "tcp://0.0.0.0:5004"
send_buffer = 1048576

[monitor]
statsd_address = "udp4://localhost:8125"

On 6/5/2022 3:41 PM, Carl Reinemann wrote:

Richard

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[Carl Reinemann]

Try editing your goesrecv.conf section to this

[rtlsdr]
frequency = 1694100000
sample_rate = 2000000
gain = 5
bias_tee = false


You might also try a gain of 6,  45 is going to introduce so much noise that not much will be decoded.  Also, be positive that your connection from dish cable to LNA and SDR are clean and tight.  Any moisture can really mess things up as well

If you haven't already, have a look at my page at https://usradioguy.com/goes-satellite-imagery-reception/

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[Pieter Noordhuis]

> I get 4 or 5 lines of zero drops then jumps to 12 drops and stays there. 

This is a tell tale sign that the signal processing gets backed up and samples from the SDR are being dropped. What kind of machine are you running goesrecv on?

If it happens to be a Raspberry Pi, beware that use of a mediocre power supply can cause CPU throttling (because of voltage drop). Some folks have had luck fixing this issue by using a power supply capable of providing 2 amps at 5V.

Cheers,

Pieter

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[richard ingram]

I have used both the Smartee XTR and the NESDR Smart. The reference to 45 gain was for the NESDR Smart, I used gain under 10 for the Smartee XTR.  Both produced very similar results.  I tried different sample rates and found that the lower the sample rate the more Zero drops I had at the start of goesrecv. With a sample rate of 1000000 I had 35 lines of zero drops at the start then drops went to about 8.  It almost looks like a buffer fills up, for sure something consistent is happening, not random.  As I said, I did a new install of goestools on another sdcard but both had same results.

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[Carl Reinemann]

Pieter and Richard, 
Yes, I agree, this has happened as well to others who have use a weak power supply, or one where moisture has got it in the supply causing the amps to drop.  Another case was person using a 20' USB extender cable, never could get the amps he needed to run the pi. Worked while testing at his table, but when he moved it outside...with extender, nothing.

Carl

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[richard ingram]

Pieter and Carl

I'm using a Pi 3B.  The power supply I have shows a 2.5A rating but I can try another.  I'm not using a long USB cable, maybe three feet.

To me the strange thing is that when I start goesrecv I get 4 or 5 zero drop lines and then it jumps to around 12 and never changes.  If I drop the sample rate to 1000000 I get 35 zero drop lines and then it jumps to about 8.  This behavior is consistent.  Maybe the Pi is not working as hard with the lower sample rate and not needing as much current, or maybe overheating.  I do have a small fan on the Pi.  I appreciate your responses.  I really want to get t a system up and running.

Richard

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[richard ingram]

Update:

I looked into the suggestion that it might be the Pi power supply causing my problem.   The one I have been using has a rating of 2.5A.  I hooked up the pi with the sdr attached and started goesrecv.  I then measured the voltage on the Pi header and it was 4.4V.  Would expect closer to 5V.  Looked around a found one rated 3A.  With that supply connected I measured 4.99V. Did a quick dish alignment for 50 degrees EL and eyeballed the AZ and started goesrecv.  To my surprise lines with zero drops came rolling in and it stayed that way.  Vit was around 250 so got lucky on the dish aiming. Started goesproc and soon started writing a file!!! Time for a drink!! Thanks to Carl and Pieter for pointing me in the right direction.  Don't necessarily believe that the amp rating states on your PS.

Richard

On 6/6/2022 7:30 AM, Carl Reinemann wrote:

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[Carl Reinemann]

Great to hear!

Carl