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vhfwxsatellitetips [2021/08/01 18:17] – [OARC VHF Weather Satellite Reception Tips & Tricks] mm3iigvhfwxsatellitetips [2021/09/24 12:29] – mm3iig
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 {{ ::meteorheader1500x500.jpg?nolink&800 |}} {{ ::meteorheader1500x500.jpg?nolink&800 |}}
 +//Meteor-M2 LRPT capture of the Eastern Atlantic and the U.K. & Ireland - MM3IIG//
  
-This is the first draft of what will hopefully become a useful club resource for people wanting to do some VHF satellite reception of either NOAA APT signals or the LRPT signal from the Russian meteor satellites. There’s no need to reinvent the wheel as plenty has been written before on this subject. Instead there will be links to other places around the Internet, but also some learned wisdom and tips from OARC members. It is unfinished and may get broken up into separate pages once it becomes unwieldy.+**Update: 24/08/21** - We’re running a club activity net on 23/09/21 for all members who want to have a go at doing some captures. Details [[vhfwxsatellitetips-activitynight|here]]! Edit: no we aren't...
  
-VHF satellite work is the easiest satellite reception work to get into. If you get the bug after doing this consider moving up to L-band HRPT reception, which should doable with a modest antenna. The next step up from that is to geostationary satellites, where you'll be needing amplifiers, filters, and a whole lot of kit. There are a few places on the internet that specialise in this kind of thing.+This is the home of what will hopefully become a useful club resource for people wanting to do some VHF satellite reception of either NOAA APT signals or the LRPT signal from the Russian meteor satellites. There’s no need to reinvent the wheel as plenty has been written before on this subject. Instead there will be links to other places around the Internet, but also some learned wisdom and tips from OARC members. The guide is split into sections and you can always get back to the index by using the breadcrumb links up at the top.
  
-----+VHF satellite work is the easiest satellite reception work to get into. If you get the bug after doing this consider moving up to L-band HRPT reception, which should doable with a modest antenna. The next step up from that is to geostationary satellites, where you'll be needing dishes, amplifiers, filters, and a whole lot of kit. There are a few places on the internet that specialise in this kind of thing.
  
-===== Contents =====+To-do: Finish the antenna section (plus links!), maybe a bit more about radio choice, and any other suggestions that you guys want.
  
-  * [[vhfwxsatellitetips-antenna|Antenna considerations + links to projects]] +Mark MM3IIG
-  * [[vhfwxsatellitetips-hw|Extra Hardware]]+
  
 ---- ----
  
-====== Software overview + tips ======+===== Contents =====
  
-===== SDR Receiver software ===== +  * [[vhfwxsatellitetips-antenna|Antenna considerations + links to projects]] - some links to plans, discussion on options, and some tips from members 
- +  * [[vhfwxsatellitetips-hw|Hardware overview]] - including SDRs/radios, low-noise amps, and bandpass filters 
-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 - but it is 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. +  * [[vhfsatellite-sw|Software overview + tips]] - some of the software used to do this work is awful - here's some useful tips for various APT/LRPT applications 
- +  * [[vhfsatellite-general|General tips/data for APT and LRPT decoding]] - some discussion on the signals in general, a list of frequencies, and some last-minute "gotchas" to avoid 
-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. +  * [[vhfsatellite-gallery|OARC reception gallery]] - some shots from around the club
- +
-Here's the most cited/arguably the best setup guide for the SDR# path: https://happysat.nl/Setup_Meteor/Setup.html - 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 ===== +
- +
-==== WxtoImg ==== +
- +
-**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. +
- +
-**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. +
- +
-**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. Same tips here as for composites: make changes to each image individually! Another tip is to scale the timing/frames to match any big 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. +
- +
-**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). +
- +
-==== NOAA-APT ==== +
- +
-**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. +
- +
-==== SatDump ==== +
- +
-If you don’t need map overlays for your LRPT captures then SatDump is a great solution that does everything you need and chucks out good images of a few different types. It’s certainly easier than setting up SDR# and multiple plugins and decoders and also opens up the world to further decoding of other satellites in other bands. +
- +
-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. +
- +
-==== LRPT Decoder ==== +
- +
-Symbol .S/.soft files 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! +
- +
-Additionally, the ini files are what tell the software what 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. +
- +
-==== MeteorGIS ==== +
- +
-Honestly, don’t worry if you can’t figure this out. The software is absolutely horrible and very much part of the “someone made it work for them and then stopped caring” school of software development. As you’ll see from the pages online it has a specific list of requirements for things like folder and file names and the command line is unforgiving if you’re doing post-pass decoding. If you’re set on projections/composites/map overlays then it’s your only option, sadly. +
- +
-(Put some useful commands here)+
  
 ---- ----
  
-====== General tips/data for APT and LRPT decoding ====== +===== Community Links/Further Info ====
- +
-<WRAP left round info 25%> +
-===== Frequency list ===== +
-  * **NOAA-15:** 137.6200 +
-  * **NOAA-18:** 137.9125 +
-  * **NOAA-19:** 137.1000 +
-  * **Meteor M-N2:** 137.1000 +
-</WRAP> +
- +
-Obviously for those of you wanting to do LRPT as well you will have to deal with the overlap and shared frequency of NOAA 19. This is always irritating and there isn't much you can do. An APT signal will destroy a digital LRPT signal, and if you try decoding APT with LRPT in the background it will show discernible shapes, but nothing really useful to work with. The best thing to do is to wait a few days for their orbits to diverge from each other. +
- +
-**APT:** FM, 34 kHz signal, set filter bandwidth to around 35-40 kHz. If you’re correcting for Doppler you can maybe go towards the lower of the range to block out more of what you don't need, but if not go for 40 to get the whole thing in and account for the +/- Doppler difference, approximately 3 kHz. +
- +
-**LRPT:** FM, 120 kHz signal, set filter bandwidth to around 130-140 kHz. Doppler correction isn’t strictly needed as the demodulator tools can pick out the data and lock onto it just fine. An SNR of around 10 dB will decode fine, but you may even get some data coming through around 5-10 if you're lucky. Just don't expect a great, error-free capture. Once you hit around 15-20 dB you're laughing. +
- +
-For LRPT work remember that it’s the raw I/Q baseband recording that you want if you aren't decoding live, not an audio recording. For APT you want the audio recording. +
- +
- +
-<WRAP center round important 60%> +
-If you’re switching between receiving the two types of signal don’t forget to check your Doppler/recording settings are suitable for each one! MM3IIG has lost more than one capture because of this kind of silliness... +
-</WRAP> +
- +
-If you can avoid DC spikes by using offset tuning or a filter function it can help, particularly with LRPT. If it’s baked into your recording and you're using SatDump then there’s an option to block it as the file is read. +
- +
-You'll need more gain for LRPT signals because of the similar power but lower bandwidth (power density). This can induce intermod/breakthrough depending on your antenna, location, etc. If that happens you may want to look into bandpass filters for 136-138 MHz. +
- +
-===== Audio Samples ===== +
- +
-Here's a couple of audio samples to test your software setup with. There's a WAV audio recording for APT and an LRPT test with a baseband I/Q WAV recording (i16, 250000 kbps sample rate). +
- +
-<WRAP left round info 40%> +
-==== APT Sample ==== +
-11,025 kHz mono WAV file, (size here) +
-  (link here) +
-</WRAP> +
- +
-<WRAP right round info 40%> +
-==== LRPT Sample ==== +
-250 kHz wide baseband I/Q WAV file, (size here) +
-  (link here) +
-</WRAP> +
- +
----- +
- +
-====== OARC reception gallery ====== +
- +
-If you're adding entries please add the start time of the pass, or for composites feel free to specify a time range. +
- +
-===== APT Captures =====+
  
-^  Capture  ^  Date  ^  Time(s) (UTC)  ^  Callsign/Name  ^  Notes  ^ +There’s lots of places where you can find some more information on reception, software, antennas, and all other relevant topics:
-^  [[https://ibb.co/QvKHgWT|{{https://i.ibb.co/QvKHgWT/07211107-MSA.jpg}}]]  |  21/07/2021  |  11:07  |  MM3IIG Mark  |  NOAA-18, Multi-spectral analysis  | +
-^  [[https://ibb.co/3TmrQCB|{{https://i.ibb.co/3TmrQCB/0721-Composite.png}}]]  |  21/07/2021  |  9am-12pm  |  MM3IIG Mark  |  NOAA-18 & 19 composite, Multi-spectral analysis. This is composed of 4 passes  | +
-^  [[https://ibb.co/SRXn11L|{{https://i.ibb.co/SRXn11L/noaa-18-07151040-norm.png}}]]  |  15/07/2021  |  10:40  |  M7SMU Simon  |  NOAA-18, normal view of a single channel  | +
-^  [[https://ibb.co/q0dK8Hn |{{https://i.ibb.co/q0dK8Hn/4256-B1-EF-02-BE-481-C-BA30-8-F6-F79-A1-EE12.gif}}]]  |  26/07/2021  |  8am-11am  |  M7SMU Simon  |  Animation created by MM3IIG using Simon’s captures  |+
  
-===== LRPT Captures =====+**Reddit:** https://www.reddit.com/r/amateursatellites/ - Amateur Satellites subreddit, which does lots of weather satellite reception as well as amateur radio satellites.
  
-To follow.+**LibreSpace:** https://libre.space - Has a forum where you can ask about reception and rotors/tracking etc.
  
-^  Capture  ^  Date  ^  Time(s) (UTC)  ^  Callsign/Name  ^  Notes  ^ +**Twitter:** Putting terms such as “meteor”, “LRPT” and the names of the NOAA satellites into Twitter can net you lots of new people to follow who are good sources of help, plus images of passes you can compare your captures with. A lot of the people on these places overlap, though. The community is a small but friendly one.
-^  [[x|{{x}}]]  |  x  |  x  |  x  |  x  |+
vhfwxsatellitetips.txt · Last modified: 2022/05/08 01:39 by mm3iig