NOAA Decoding

[Spartanman]

Hi,

Im trying to decode NOAA images with mi SDR but i dont take a good signal and there is a lot of noise.
¿How can I improve it?



This is the best one i have. The satellite over Spain.

 

[PDXh0b0]

What is your setup ? Type of antenna and placement? Is that image cropped, or the full recorded pass? If using wxtoimg, you'll need to manually update your tle's
You could copy and paste this into a text editor, save as .bat file, or just paste it into a cmd window

powershell -NoExit -Command Invoke-WebRequest http://celestrak.org/NORAD/elements/weather.txt -OutFile $env:userprofile\AppData\Roaming\WXtoImg\weather.txt

If a v-dipole I'd start with the antenna hieght at 1.5 meters
Automatic Picture Transmission (APT) - Signal Identification Wiki

 

[wx2watch]

For the NOAA satellites (APT), the antenna is EVERYTHING.

If I were to guess, the OP probably is trying to improvise regarding the antenna.

Over the years, I tried many homebrew antennas (of my own making) but nothing beats a quadrifilar helix antenna. (see picture)

Well, actually, if you have an old NASA 85 ft dish, that would be better... (BIG grin) see my icon for a better perspective

 

[PDXh0b0]

V-dipole

 

[wx2watch]

V-dipole

Very nice. Given my poor experiences with homebrew antennas, I am truly impressed!

 

[CanesFan95]

What frequency and softawre is this?

 

[wx2watch]

Very nice. Given my poor experiences with homebrew antennas, I am truly impressed!

Hmmm, have not seen any response from the OP as to what antenna he is using. So, thought I would pass along a picture of the two antennas I mentioned.

Also, a question for PDXh0b0. How well does your antenna handle non-directly overhead signals from the NOAA birds?

i.e. Any "drop-outs" if the bird is only, say, 26 degrees above the horizon as opposed to 90 degrees/directly overhead?

Thanks,
John

 

[Spartanman]

Hi, i use the default anthena of the sdr...
Im thinking on doing one my own. Any recomendation?

 

[wx2watch]

Well, my personal preference is the QFH as that is the same type of antenna used by the NOAA spacecraft for APT transmissions. BUT, be aware that it is VERY demanding in that all the curves have very tight tolerances. (In the past, there used to be web sites with the specs but I don't know if they are still available)

PDXh0b0's v-dipole looks like it works well with a much simpler construction scheme. (Thank you for the Wiki link!)

If you have the storage space - My very first APT antenna was a home brew 6-turn helical. It worked well but was over 12 feet in length. (big GROAN!) Also, I had it mounted on a 5 ft tripod that required me to manually track the bird by hand. (The proverbial "Armstrong Rotator!)

But , most anything will be better than the "rabbit ears" that typically come with rtl-sdr dongle. Although you might get lucky if you have a directly overhead pass - periods of strong signals but with frequent drop-outs.

Good luck and let us know how it goes (pun intended). But you better hurry as those NOAA birds are an endangered species - They are operating on borrowed time.

 

[PDXh0b0]

Also, a question for PDXh0b0. How well does your antenna handle non-directly overhead signals from the NOAA birds?

i.e. Any "drop-outs" if the bird is only, say, 26 degrees above the horizon as opposed to 90 degrees/directly overhead?

Thanks,
John

I start seeing drops at around 18°

I sit below a ridgeline north to east of me, mountain south to west behind me

I set up once in a mountain top park and caught 3 passes of each sat

And the are days, when the passes are crap.

I ran my v-dipole and my qfh about 20ft apart same length of coax, two identical laptops, identical sdr's, identical usb extension cables. V-dipole did better on average. I made the qfh with 12 awg solid copper, I plan a rebuild with 1/4 copper tubing (went to local ace couple days ago, they no longer stock it 🤨) thinking I try a tall/long version this time around.

 

[Spartanman]

Hey. Im posting a audio file recorded ten minutes ago. Lets see if someone can do something with it.
Tell me if you can acces or not.

GitHub - Spartandman/NOAA-AUDIO-RECORD: NOAA AUDIO RECORD

NOAA AUDIO RECORD. Contribute to Spartandman/NOAA-AUDIO-RECORD development by creating an account on GitHub.

github.com

 

[PDXh0b0]

open-weather apt — satellite image decoder

open-weather apt is an accessible browser based decoder for National Oceanic and Atmospheric Administration (NOAA) satellite images.

apt.open-weather.community

 

[Spartanman]

open-weather apt — satellite image decoder

open-weather apt is an accessible browser based decoder for National Oceanic and Atmospheric Administration (NOAA) satellite images.

apt.open-weather.community

 

[dlwtrunked]

Hi, i use the default anthena of the sdr...
Im thinking on doing one my own. Any recomendation?

If you mean the antenna that came with an RTL-SDR, you should have immediately thrown that antenna away and kept the SDR. I am serious.
It is a small simple whip not designed for the frequencies that you are interest in. For just any receive purposes, there are much better choices.

 

[Spartanman]

If you mean the antenna that came with an RTL-SDR, you should have immediately thrown that antenna away and kept the SDR. I am serious.
It is a small simple whip not designed for the frequencies that you are interest in. For just any receive purposes, there are much better choices.

And what are the options?

 

[wx2watch]

As dlwtrunked indirectly alluded to, a simple whip antenna (even if cut for 137 MHz) will not do the proper job of receiving the APT signal. The APT signal uses circular polarization. (I do not recall which flavor of circular for APT, either right handed (RHCP) or left handed (LHCP)).

A simple whip antenna is going to be either horizontal or vertical polarization, either of which will give poor results for APT service.

IIRC, the APT antenna must either be physically similar to the wave form (e.g. omni-directional QFH antenna) or helical (VERY directional antenna). The linear looking v-dipole antenna achieves this by a bit of electro-mechanical phase trickery.

Although the physics of why we use circular is above my pay grade, I believe it has something to do with something called Faraday Rotation as the signal transits through the atmosphere from the spacecraft to the ground station.

Probably not the simple answer you were hoping for but at least you know what to NOT look for in the way of an antenna for APT.

 

[PDXh0b0]

And what are the options?

Is it the Rabbit ears antenna? Inside or outside?

 

[K5MPH]

Take some ol tv rabbit ear antenna and spread the elements 120 degrees apart and put it vertical .......

 

[MikeTheListener]

Not everyone has the space for special antennas or is simply not allowed to set them up (prohibited by the landlord).
I only have a Diamond X-30 that I use for receiving the NOAA satellites. Of course, the results are not 100%, but I think they are quite impressive. Of course, there is always a better way, but then the question is "how high is the effort and how much money do you have to spend".

 

[ArloG]

Yeah. I use a 137 MHz QFH. A discone will receive NOAA and Meteor with marginal results. A bias tee LNA makes a world of difference. Especially if you can put it close to the antenna. Also make sure you start out in FM mode with a 40 kHz IF bandwidth. Lower it a bit to reduce noise in the image if the signal is weak. And use AFC or manually track the frequency to correct Doppler shift.