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Software overview + tips

SDR Receiver software

Honestly, it doesn’t really matter what software you use as long as it can pipe out audio to a virtual cable or record the audio or baseband for use later (for APT be sure to resample recordings to 11,025 kHz with your software of choice - see below). For LRPT you may wish to use SDR# as the plugin and setup is well-supported, but it can be difficult to get set up right. Alternatives are available, such as the excellent SatDump suite (which does a lot more besides VHF and can also decode the NOAA VHF telemetry streams). It does not, sadly, do APT yet, nor can it do LRPT map overlays, but these features are being added at some point soon. It can also work with RTL-SDR dongles for live decoding, which makes for an all-in-one solution when it’s all complete.

If you’re struggling for CPU clock cycles you can run with a low sample rate for this work. This is useful for RTL-SDR dongles. Both signals easily fit into a 250kbps sample rate. This also makes it doable on RPIs, but processing the data afterwards can take longer than other devices.

Here's the most cited/arguably the best setup guide for the LRPT SDR# path: - If you're going with SatDump (which can now do live captures with some SDR hardware!) then just record your baseband and load it in. The user interface is quite simple (see below for more tips).

For APT there's lots out there already and it's just a simple virtual audio cable setup. If you’re struggling with stuttering audio then you’ll definitely have sync issues - the odd jump is fixable, sustained losses of data or gaps in the audio are not. There are resources available on how to adjust settings to try and fix this, but also your computer may just be not powerful enough.

Demodulation, decoding and processing software


Overriding pass auto-recording - you may need to tell WxtoImg to stop enabling recording when you’re trying to do other work in it. The best way to do this seems to be to deactivate the specific satellite the software is trying to record next from the list of satellites in the options - or untick them all. You may also need to do this to record one particular satellite if two passes are happening at the same time. Sadly, you may not be able to get into the menus in time after you load to cancel a record, so sometimes you may just have to wait 10 minutes or so for the pass to complete before reopening the application.

Composite tips - make sure that you make any changes to an image individually before saving the composite (that is, any of the options under the Image menu, such as equalising the image). Also images are saved in the order you add them to the composite - remember this when you’re after a certain image in a certain place. For example, two passes may cover the same area, but you want one shot over the other because it has better clouds or less noise.

Animations - it works, but it’s ropey, depending on the AVI format you choose. It may be better to transcode to MP4 afterwards if you want to do anything with it. Or you could save images out individually and use an app that doesn't suck to compile the finished product. Same tips here as for composites: make changes to each image individually! Another tip is to scale the timing/frames to match any big time jumps, or you could try and do some interpolation? There’s lots of options. Captions would be good too, but you’ll need to edit your images or use a video editor app.

Desyncs/missing data - If you have a desync (such as jumps caused by interruptions in the audio - whether via a virtual cable or a real source) other software may be able to fix the WAV! NOAA-APT’s “Resample WAV” function under the Tools menu can process a WAV and then you can bring it into WxtoImg to do more work. It doesn’t always do it brilliantly, but small errors can be worked around.

Importing audio files tip - If you are bringing any audio file back into WxtoImg you will need to clone the timestamp from the original recording! If you don’t you may find your map overlays don’t work right. Again, NOAA-APT has a function for this in the Tools menu. Sometimes you may find a pass you copy into the audio folder isn't matched up with a pass in the Audio Files tab, so you'll have to load those WAVs manually.

Recording passes for longer - If you improve your antenna’s low-angle gain make sure to adjust how early/late in a pass the recording runs. This can be found under Recording Options and is set by elevation angle on each side (useful if you’re blocked on one side - you can ignore it). Set a starting angle (bottom box) and a max elevation above which you want a recording to happen at all (top box).


Enhancements - NOAA-APT is a bit crap in this department, particular in how it handles the false colouring of images. See what you think - this is going to be a personal choice. If you find a good position for the sliders then well done!

Map overlays - this actually works well (and the adjustable-per-second correction can be very useful vs the fiddly WxtoImg “drag map overlay” option or messing about with timestamps). You will have to make completely transparent the lines you don't want to see, however, as you can't toggle things on and off.


Loading baseband recordings - Do make sure you select the right sample rate (bandwidth selected in SDR application) and type when loading in your baseband. The box expects bits per second, rather than kilobits per second. Tick DC Block too if you know you have a spike in your recording.

LRPT Decoder

Loading .S/.soft files - These have to have a specific filename or they won’t show up in the file open box, even if the extension matches. The format is that put out by the SDR# demodulator plug-in. If you want to load in a renamed file or a file from something else like SatDump you’ll need to type the first few characters and you’ll be able to click on the one you want. Annoying. That’s ham radio software, though!

Configuration .INI files - The ini files are what tell the software which mode you want to be in - you can drag the included ini files onto the exe file to start a particular one (after editing them to suit your needs) or you can rename one to the same name as the main ini file. The former option gives you more flexibility. You could even set up some .BAT files on your desktop to start in each mode. Perhaps in the future the developer will add the option to change modes within the software. You also have to quit and reload the app after each operation, it seems.


I am using a “measuring tape” turnstyle antenna mounted at 5 m high. 30 m of coaxx,a nooelectric twin LNA's with saw filter for 137 mhz. The LNA is Bias T powered by the RTL SDR dongle. All the passes are processed by a suite of software which includes orbitron,sdr sharp,lrpt decoder.dde control and meteorgis. The only setup for meteor m2 processing is to set location and time offset in orbitron and location in meteor gis. The system waits for a meteor pass and switches SDR# on with lrpt active. After a pass MeteorGIS processes the image to create country overlays and composites The system can also be used for NOAA passes by selecting the sats in orbitron, configuring audio output in SDR# and starting Wxtoimg The suite of software for win 10 is preconfigured in a single zip file for extraction to the root of any drive. For more information and downloads see:

A good source on using MeteorGIS can be found at :

Reprocessing Meteor M2 Images

The attached zip file is a package put together by Les Hamilton. It allows you to reprocess any .s files you may have. These could have been created by any combination of software that suits you. The package will reprocess a .s file to remove black lines, assign a projection such as UTM, sharpen the image and overlay country borders etc. The readme.pdf included has the step by step procedure. Simply unzip the .zip file into the root of your drive.

vhfsatellite-sw.txt · Last modified: 2022/05/08 01:40 by mm3iig