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Openplotter 2 Weatherfax Plugin for OpenCPN
#1
How do I configure the RTL SDR dongle for usage with the OpenCPN Weatherfax plug-in on a raspberry pi?
I can only choose the onboard soundcard, which I will not be using. I've tried this for a time, but I cannot get it to work.
Does anybody have some knowledge about this?

I've read in another forum that the OP2 SDR VHF app will be extended with SDR-HF, but I don't see the option yet when configuring the app.
I really want to use weatherfax badly, but I do not want to manually use GPRX or any other recording software. The weatherfax schudule option is just too good and easy to use.

Hope someone can help!
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#2
the openplotter-sdr-hf will be a new and independent app but we are not working on this right now.

AFAIK opencpn weatherfax plugin is only for audio capture not for SDR. You should ask to plugin developers.
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#3
Thanks Sailoog,

I've asked Sean on his Github, but I was also curious about experiences in the openmarine community. I've also looked for some posts on cruisersforum, but they were at bit older, what made me bring this up in here. Sorry if it is off topic, but I thought the people who might have experience with it might be active here, so I was looking for some opinions.

I am very, very curious about the openplotter-sdr-hf app that you are planning, hope to read about it more in the future. Smile
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#4
(2020-07-28, 01:40 PM)jamos.tan@gmail.com Wrote: How do I configure the RTL SDR dongle for usage with the OpenCPN Weatherfax plug-in on a raspberry pi?
I can only choose the onboard soundcard, which I will not be using. I've tried this for a time, but I cannot get it to work.
Does anybody have some knowledge about this?

I've read in another forum that the OP2 SDR VHF app will be extended with SDR-HF, but I don't see the option yet when configuring the app.
I really want to use weatherfax badly, but I do not want to manually use GPRX or any other recording software. The weatherfax schudule option is just too good and easy to use.

Hope someone can help!

Had a play a while ago, can't remember if I had the opencpn plugin working but istr it was much more successful recording the audio direct to a file then decooding that. Think I used sox to record & set the audio file to a format the opencpn plugin of jvcomm on a laptop could decode. 
http://sox.sourceforge.net/
Might be a job for node-red? 

What RTL dongle do you have? Can it tune as low as 8MHZ to receive the fax broadcasts?
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#5
Thanks PaddyB,

Ok, if I understand right the recording itself must be done externally, not by the plugin itself. I have some experience with that, downloading satellite images directly from passes of NOAA and METEOR. A few scripts handle recording with sox, planning of sat passes with predict, and a script to convert it to images with wxtoimg (with some false overlay colors, landmarks, etc.) This operates in the 137 mhz range, and a sawfilter will improve the results. It is all automated, which is nice, but you need a QFH omni-directional antenna.

Is it possible to use the schedule of the weatherfax plugin, but modify the code so the actual recording will be done by sox?
Node-red is a nice idea, if this will work will be great too... but I am not sure how this will look like.

Currently I have a few dongles from Nooelec. I don't have an upconverter yet, and I need to look into the documentation if they can handle the frequencies. I have tested it with SDRsharp or GPQRX, and it did work when manually recording it, and to decode it with the linux programm "hamfax" resulted in the images.

An automated method would be very much preferred. I can share the previously mentioned scripts if you like.
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#6
Maybe a Pi4 could decode it in the plugin, on a Pi3 istr it was just asking too much. I have a fun cube dongle which receives all frequencies so that side was easy. Scheduling should be possible in node red maybe? If i'm looking for wfax then it will be well offshore & I've all the time in the world Smile
I've had sort of readable sat images on 137MHZ before just using the insulated backstay and a ic7000 ham radio. Fun! Smile
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#7
Sounds interesting, I have a Pi4 with 4GB laying around I can play with.
Any idea how to modify the plugin so that sox will do it's work?
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#8
By the way, I just found out that wxtoimg can listen for weatherfax start and stop tones and starts and stops recording automatically. Could come in handy.
But, you still need a standard audio input and an external radio to tune to the frequencies.

But, you cannot choose an SDR card in the audio input. To use the standard incoming audio ports for SDR you can probably do audio piping and create a virtual audio port. Not sure how to do this yet, but at least a major part of the automation would be solved in this case, not to mention the extra benefits of wxtoimg.

Now the only thing left is to autotune the sdr to the right frequency somehow, and let wxtoimg listen constantly and only start recording when the start tone is found.
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