Downloading NOAA Satellite Images Cheaply and Easily

Intro: Downloading NOAA Satellite Images Cheaply and Easily

This will show you how to download weather satellite images really cheaply and easily using easy to obtain parts.

For this you will need:
RTL SDR USB software defined radio. It costs around 20 pounds.
get it here:http://www.ebay.co.uk/itm/140803976327?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
I have discovered a problem with this radio. It does not pick up weather satellites at all any more but it still picks up everything else very well. It seems to lose sensitivity to the signals over time.

SDR Sharp. You can search Google for this.

Audacity

APT Decoder
this is a free program.
There are many places to get it

2 metre long piece of wire

long pole to hold the wire

A small laptop computer that you can hold for 15 minutes at a time.

You can connect your radio to a USB extension cable and just hold the radio in your hand rather than having a laptop under your arm. If you do this, the USB cable sometimes causes noise and signal loss so it is best to have the radio plugged directly into the laptop.




Finally, if you have really enjoyed this or found it useful, please consider making a tiny donation trough Paypal here:
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STEP 1: The Setup

I have modified my software radio that I bought by removing the existing connector and attaching a coaxial socket instead. I also covered it in foil which can help block noise in some cases.

You simply have to secure the wire to the central pin of the coaxial connection by soldering or making up your own connection. The other end of the wire is attached to the other end of the pole a bit like a fishing rod. Once you have the software at the right frequency, you close the laptop, hold it in your left arm and hold the antenna pole with your right hand until you can hear the satellite.

To set up the software so it detects the radio, you need to copy rtlsdr.dll into the same directory as SDR Sharp.
A better guide will be included with your radio or you can find it online.
In SDR Sharp, you have to set the front end option to your software radio. In my case it is RTL SDR/RTL 2832U.
You have to uncheck filter audio and you must set the bandwidth to 36 KHz. The mode should be set to NFM and the squelch off.

I find that my radio picks up NOAA 18 the best so go here to track it:
http://www.n2yo.com/?s=28654

It struggles with other satellites because there are noise spikes near the NOAA 19 and NOAA 15 frequencies. These spikes may be caused by the radio itself or USB power supply noise.

STEP 2: Downloading the Images

To begin, you need to have audacity open along with SDR Sharp. In Audacity, the recording device must be set to stereo mix and the sample rate set to 11025. Start off with the laptop on the ground and the radio set to 137.9125. As the satellite approaches, move the antenna about until the signal begins to show and click in the middle of the signal trace on the waterfall spectrum as it shows on SDR Sharp. Press record in Audacity, close the laptop and hold up the aerial for the duration of the pass. You will have to move it around at times. The frequency will also shift as the pass progresses so you may have to open the laptop and adjust the frequency slightly and resume. You will know you are getting the signal right when you hear a clear high pitched tone with a clear tick tock sound on it. I have added a sample for you here so you know exactly what to listen for. You have to set the volume in Windows to about half. Also, if you use headphones to listen as the satellite comes over, you will be able to hear it more clearly.

STEP 3: Decoding and Results

The results will vary depending on weather conditions. This picture I have added is the best one I have ever got using this method on a nice day with broken cloud. To decode, you need to open APT Decoder and load your wav file. It MUST be 11025 Hz sample rate. It does not matter what bit depth the wav is. Just use 32 bit to ensure best quality.

The ideal setup for this would be a roof mounted quadrifilar helix antenna connected to a proper satellite receiver or your software radio but this is the expensive option.

Comments

[David R1]

You need a QFH (quadra filiar helical) antenna as the signals are circular radiated. Sing whips can barely do it. They take some effort but work well, had one working for 2 years. Used 2 meter ham receiver to test 137 MHz where sats are and heard one first pass. The antenna with a dedicated amp , they are made for that band, and remote power so that amp can be mounted as close to antenna as possible realy pulls in all satellites.

[BHAGAVATHI]

Is FM Receiver antenna is applicable for this application???

[jamie-cole]

hi verry good tutorial

i have a question what way do you hold the antenia ? like on the picture or pointing up to the sky

[matokage]

Did you ever tryied using SSTV for decoding the signals?

[sdobbie]

I don't know what that is.

[sconner1]

That's really cool.

[Learndy]

NASA also publishes satellite images. They operate their MODIS high resolution multi band satellites which take images of the earth at pixel resolutions of 250m x 250m. This means that a pixel corresponds to an area of 800 ft x 800 ft on earth. They publish the MODIS image of the day which is mirrored by various web sites, e.g.: http://www.airspace-v.com/ggadgets/modis.htm where you can also find a Google gadget to get the current image of the current day.

[jhitesman]

I've done this before with a number of "real" radios but just picked up a RTL dongle and have been trying to get anything usable. Same software and antenna config that's worked for me before but just can't get a decent image with the RTL - it's just not a strong enough signal. So I'm thinking that at least the dongle I got is a little less sensitive than I had been expecting. Need to find time to do more tests to confirm. I still have a blast with it as there are all kinds of interesting things in the range it can pull in (aircraft positions, land mobile users, commercial FM, weather stations,VHV/UHF amateur frequencies....) For as little as they cost I need to pick up another of a different brand and see if it's any better. As mine just seems a little deaf compared to most that I've seen.

Oddly enough with any of my radios I've had the best luck with my HF antenna for the NOAA sats, no clue why. I've been meaning to build a circularly polarized antenna for them for a couple of years but never seem to get around to finishing it.

[Wazzupdoc]

Try adding a pre-amp at the antenna. Ramsey makes one for about $20US. That should give your images a boost.

[jhitesman]

Well, like I said I have a number of other "real" radios that work just fine for receiving WX sats with my existing antennas. The RTL dongle just isn't very sensitive. I have a pre-amp but it if comes down to that I'd rather just dust off one of my real radios that have a more sensitive receiver. A pre-amp won't make the receiver in the RTL any better - it may just help mask the problem, or it could make it worse since a pre-amp will also raise the noise floor which is already really high on these little dongles. Building a better antenna will probably give more signal gain and have fewer drawbacks than a pre-amp. Plus I can build a good antenna out of things I have laying around without spending another dime ;)

Same deal for soldering a new connection, these boards are tiny, the traces are tiny, and they're really cheap so it's easy to break/lift a trace. Adding a new connector will help get a slightly better signal from the anteanna by removing a few db of losses from the adapters - but it's also going to create a whole host of it's own issues I'd rather not deal with.

Instead I just accept that the $20 dongle has it's place. It's a ton of fun for listening to strong terrestrial signals but just isn't great as a ground station for sat work. It's great for listening to the local repeaters - but can't decode 1200 baud APRS transmissions reliably either. I can hear lots of APRS activity - but it never gets decoded. Most likely the computer I'm using it on is a little underpowered as well which isn't helping. But I've got a shoebox full of softrock RX's that work great for HF. I just really wanted one of these for all mode VHF/UHF to complement my softrocks and for $20 I got more than my money's worth. But that isn't to say it's a great radio.

[sdobbie]

You should try soldering a large coaxial connection directly on to the circuit board on the radio.

[khourig]

You know NOAA has a web site for this information, right?

http://www.nesdis.noaa.gov/SatProducts.html



Anyway, I appreciate the HAM aspect of getting this signal direct and decoding it. Good job.

[billgeo]

That's really fantastic.

Will this work around the world or its limited to some countries?

[sdobbie]

It works anywhere.

[CShaffer212]

What's the reason to close the laptop?

[conmac863]

I think it is so you can stick it under your arm but that is a guess.

[CShaffer212]

Ah, yes. That does make sense.

[sdobbie]

That is the reason, so I can put it under my arm. I am now using an Iconia Tab W500 which is much lighter.

[dan.berry]

I believe the author suggested this because LCD panels emit strong spikes across a number of frequencies as they operate (thanks to harmonic distortion).

Given that he has taken the step of wrapping the SDR dongle in foil, I'm assuming he's further doing this to minimize any noise interference.

[TheBlackSharpie]

Is this legal?