Monday, February 17, 2014

NOAA APT images received using RTL DVB Dongle

This is a time-lapse video of NOAA-19 being received using Sdrsharp,  Wxtoimg and homebrew QFH antenna. 

8 min video is made to fit in 1:08min.

Or watch it from my dropbox with better resolution.

I used Sdrsharp to tune rtl and Wxtoimg freeware for decoding NOAA APT images,  but you can use below mentioned procedure which is far more automated. I have tested it and works well as it has Doppler correction. 

Please note that this article is not written by me and you may find higher version of this document (v0.1b (29 June 2011) on the internet.

Using HDSDRs built-in DDE client

HDSDR v2.0 may be frequency controlled via DDE. DDE stands for Dynamic Data Exchange. It is used to share information between different software programs. Having the capability to control your software defined radio's Tune or LO frequency via DDE is especially helpful when dealing with doppler correction in Satellite and EME based communications. The example below will
show you how to configure Ham Radio Deluxe's Satellite Tracker to control the LO of a Softrock VHF Ensemble kit for doppler correction. It is assumed you already have successfully configured HDSDR with your software defined radio and the program is operating. Only minor changes if any will have to be made to the instructions below for use with other software defined radio's HDSDR supports.For linear transponder satellite operators, the capability to view the entire transponder at once is an invaluable tool. For satellite operators not familiar with software defined radio, imagine being able to view and record the entire transponder at once.

The advantages are tremendous:
- Quickly visually identify existing QSO's and stations calling CQ
- Quickly visually identify who is using software doppler control
- Record and play back the entire transponder to hear all stations on the transponder which you did not make contact with
- Quickly find on the transponder stations which you have limited   mutual visibility with
- Never have to wonder if there is someone else on the transponder you could be contacting while you're currently engaged in a QSO
- No need to purchase an expensive full duplex all mode radio or two all mode half-duplex radios. A half duplex radio and software defined radio, such as an inexpensive Softrock VHF Ensemble (which requires 15dB pre-amp) is all you need.
Configuring HRD SatTracker:
- Download and install Ham Radio Deluxe version 5
- Run the HRD Satellite Tracking sub program
- From the top menu select Tools  >>> Options Make the suggested in each tab below.
- Enter your 4 or 6 digit grid square under Your Information >>> Locator
- DDE Local Server >>> Select Orbitron
- Click OK on the bottom right of this window
- On the top iconed menu bar click on the Satellite Defns button
- Click Add Group on the sub-iconed menu bar that shows up
- Come up with a name for the Title: field
- Now choose the satellites you want to track. Some good ones linear transponders with 2m downlinks are VO-52 and AO-7. Visit for status updates on current satellites.
- Close the Satellite Definitions Tab
- On the main iconed top menu bar click on Next Passes, which has a blue arrow on its icon in the top Menu. You will now be able to see when the upcoming passes will over you.
- Double click on a satellite's elevation vs time graph, say VO52 which has a loud USB 2m downlink. A new tab will open showing VO52's current foot print on Earth.
- On this new tab's sub-menu icon bar click on Tuning Dial
- VFO-A and VFO-B will appear. Double click on either one
- Double click on the RX frequency of 145.900.
Hint: If your SDR has a "hump" or a lot of noise at the center frequency, you might wish to offset 145.900 by 10-15Hz, as 144.900 is the center of the transponder where most of the activity
will take place. This can temporarily be done by using the TRX slider as well.
- Check the RX box next to VFO-A. Checking this box will send the doppler corrected frequency via
Configuring HDSDR:
- Launch HDSDR
- Press the F7 key to bring up the Options menu
- Select DDE Client
- Choose Orbitron for DDE Format. You should see "Status: connection ok :)" text.
- Choose LO for Sync type
- Click OK
- Notice HRD Satellite tracker is now adjusting your LO frequency for doppler shift
For higher frequency EME use where doppler is an issue, Moon can be chosen as the satellite to track in HRD Sat tracker under the Add Group section above. HRD can be configured to control your transmitting radio directly and send the doppler corrected RX frequency to
v0.1b (29 June 2011)


  1. Hi Mahesh,

    What antenna setup do you use with the RTL SDR ?? I tried monitoring the NOAA, but dont even get a faint signal with a ground plane. Please suggest.