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Old 12-04-2021, 20:06   #1
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Weatherfax and SDR

I’ve been messing around with SDR recently and have a dongle and an HF “Ham it Up” antenna “frequency adjuster”.

I was watching this video explanation of weatherfaxes: https://www.sdrplay.com/new-hf-weath...rial-released/

In the video, it mentions a “virtual audio connection” between the SDR and the weatherfax decoder software. I looked into OpenCPN Weatherfax and see I can download an audio file for it to decode, but was wondering if a virtual connection between SDR and WeFax plugin is possible. Sort of cut out the middle man.

I don’t have an SSB nor have any plans to get one, but with SDR on board, WeFax might be viable if I hook it up to my isolated back stay.

Anyone have any guidance on this?

Steve
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Old 12-04-2021, 20:28   #2
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Re: Weatherfax and SDR

Why not just download the weatherfax with email instead of messing around with the audio file?
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Old 13-04-2021, 02:51   #3
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Re: Weatherfax and SDR

Weatherfax can direct download from the internet, so email isn’t necessary. I’m interested in learning about how to use it if there is no internet connection. Then the audio file might be the only option.
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Old 13-04-2021, 03:45   #4
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Re: Weatherfax and SDR

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Old 15-04-2021, 16:31   #5
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Re: Weatherfax and SDR

Some years ago I had to shelter for a few days away inside a sea lough on the west side of the Isle of Jura, where there was no habitation for many miles and no VHF reception. I regretted not having maintained even a simple HF receiver like that mentioned below. I have since made amends, and quoting from my post #1258 just 3 years ago: "My antenna setup was described in a previous post, with a little modification - I now use R58 coax clipped to the backstay with the screen clipped to the rudder stock as an earth. The other end is coiled around a ferrite bar salvaged from a vintage radio direction finder, then to an old atu module from a military surplus HF manpack, then to the rtl-sdr.com dongle and from there to a Dell notebook. The dongle is controlled by SDRSharp, and piped to OpenCPN using Virtual Audio Cable (VAC). I'm afraid have no knowledge of Linux, and have yet to succeed in in getting the rtlsdr plugin to control the dongle.
This setup allows me to get very clear images from Offenbach which is over 1,000 klms away.
In the past I have had success with a Sony 7600, and later a Degen DE1103 with a little tuned loop antenna. The Degen SSB tone control (these SW sets have a circuit called a Beat Frequency Ossilator - BFO to put a tone on each SSB) is much more sensitive than the earlier Sony model, and it can also recharge it's own batteries"
The dongle mentioned is the version 3 which does not need any upconverter for HF and has excellent frequency stability on an accuracy of -1 PPM. Configure the SDRSharp Sampling Mode to Direct sampling (Q branch).
When VAC is installed select Line 1 in the Audio/Output box on SDRSharp and the Preferences box in OpenCPN Weatherfax plugin picks that up when Audio is selected there. The best frequency for me to get wefax from Offenbach DDK is 7,878.5 khz USB with 3,000 BW. If using a laptop/notebook you sometimes get "stepping" on the picture, which comes from interrupt routines in the operating system and is mostly resolved by switching off any battery saving routines and ensuring the the battery is fully charged. This "stepping" can make the image unusable for the morphing procedures in the plugin.
My best frequency for Northwood wefax is 4,608.5, but Offenbach is much better. I also managed to get a poor image once from Boston on 9,108.5 when on the SW coast of Ireland.
I also use Multiplex which does not need SDRSharp to decode SYNOP/SHIP transmissions, also from Offenbach, on 7,644.507 khz.
As you can see these frequencies are 1.5 khz down from the published frequency to allow for the sideband.
I can also tune & decode Navtex by using SDRSharp with Fldigi, and of course any HF voice transmissions can be heard just on SDRSharp.
All of the aero and marine frequencies can be tuned by switching to a different antenna, as well as broadcast stations
A neighbouring boater who is an electrical engineer and a HAM showed me a modern ATU about the size of a matchbox with a small loop antenna which he uses, but I have not seen his wefaxes. I'm sure the large ferrite rods and ferrite inductors in my old ATU filter an awful lot of noise and interference.
RTL-SDR.com has an article about a hacked GPS antenna to tune satellite maritime communications which I have yet to be successful with.
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Old 15-04-2021, 19:04   #6
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Re: Weatherfax and SDR

Quote:
Originally Posted by Maelruan View Post
Some years ago I had to shelter for a few days away inside a sea lough on the west side of the Isle of Jura, where there was no habitation for many miles and no VHF reception. I regretted not having maintained even a simple HF receiver like that mentioned below. I have since made amends, and quoting from my post #1258 just 3 years ago: "My antenna setup was described in a previous post, with a little modification - I now use R58 coax clipped to the backstay with the screen clipped to the rudder stock as an earth. The other end is coiled around a ferrite bar salvaged from a vintage radio direction finder, then to an old atu module from a military surplus HF manpack, then to the rtl-sdr.com dongle and from there to a Dell notebook. The dongle is controlled by SDRSharp, and piped to OpenCPN using Virtual Audio Cable (VAC). I'm afraid have no knowledge of Linux, and have yet to succeed in in getting the rtlsdr plugin to control the dongle.

This setup allows me to get very clear images from Offenbach which is over 1,000 klms away.

In the past I have had success with a Sony 7600, and later a Degen DE1103 with a little tuned loop antenna. The Degen SSB tone control (these SW sets have a circuit called a Beat Frequency Ossilator - BFO to put a tone on each SSB) is much more sensitive than the earlier Sony model, and it can also recharge it's own batteries"

The dongle mentioned is the version 3 which does not need any upconverter for HF and has excellent frequency stability on an accuracy of -1 PPM. Configure the SDRSharp Sampling Mode to Direct sampling (Q branch).

When VAC is installed select Line 1 in the Audio/Output box on SDRSharp and the Preferences box in OpenCPN Weatherfax plugin picks that up when Audio is selected there. The best frequency for me to get wefax from Offenbach DDK is 7,878.5 khz USB with 3,000 BW. If using a laptop/notebook you sometimes get "stepping" on the picture, which comes from interrupt routines in the operating system and is mostly resolved by switching off any battery saving routines and ensuring the the battery is fully charged. This "stepping" can make the image unusable for the morphing procedures in the plugin.

My best frequency for Northwood wefax is 4,608.5, but Offenbach is much better. I also managed to get a poor image once from Boston on 9,108.5 when on the SW coast of Ireland.

I also use Multiplex which does not need SDRSharp to decode SYNOP/SHIP transmissions, also from Offenbach, on 7,644.507 khz.

As you can see these frequencies are 1.5 khz down from the published frequency to allow for the sideband.

I can also tune & decode Navtex by using SDRSharp with Fldigi, and of course any HF voice transmissions can be heard just on SDRSharp.

All of the aero and marine frequencies can be tuned by switching to a different antenna, as well as broadcast stations

A neighbouring boater who is an electrical engineer and a HAM showed me a modern ATU about the size of a matchbox with a small loop antenna which he uses, but I have not seen his wefaxes. I'm sure the large ferrite rods and ferrite inductors in my old ATU filter an awful lot of noise and interference.

RTL-SDR.com has an article about a hacked GPS antenna to tune satellite maritime communications which I have yet to be successful with.


Thank you, Maelruan! This is the best description I’ve found so far. A lot of what you say makes sense. I have a Ham-it-Up converter, which I think I’m misunderstanding. I’ve been looking at single dongles (version 3 as you mentioned), to simplify things. Not there yet.

Thanks for letting me know what I want to do is possible. I’ll keep at it.

Steve
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Old 16-04-2021, 06:23   #7
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Re: Weatherfax and SDR

I worked on this years ago with the ham it up converter using weather fax plugin.


I added support to the plugin to automatically tune the dongle, so you could automatically schedule faxes from various frequencies at different times. I don't think this will work on OS other than linux at this time.



I found the picture from the ham it up with sdr to be lower quality than using a tecsun pl600 receiver. So, for this reason I did not persist as the quality was never very good.
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Old 16-04-2021, 06:54   #8
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Re: Weatherfax and SDR

Thanks Sean. Another reason to look for a different dongle. I’ll mess around with this some more later.
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Old 16-04-2021, 07:47   #9
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Re: Weatherfax and SDR

Thanks Maulruan for your excellent description.

I found the same
". I'm afraid have no knowledge of Linux, and have yet to succeed in in getting the rtlsdr plugin to control the dongle." Good to know.
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Old 16-04-2021, 07:50   #10
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Re: Weatherfax and SDR

BTW.
It is past time to update all of the weatherfax source files for this plugin. Please send your local channels and favorite sources.
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Old 16-04-2021, 09:16   #11
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Re: Weatherfax and SDR

Hi Rick,

I've transitioned my from Macs on board to RPi 4s (they run off of 12 volt transformers, so no more inverter needed). So I hope to continue to look at this and will look into Sean's suggestion of using Linux do exactly what I want it to do -- remove the human element (namely me) where possible. One thing I know, if I leave it to me to do something, I'll forget or screw it up, so automation is desirable where it is safe and practical to do so. That's what makes people like you, Sean, and Maulruan so important to our community here and I'm grateful for the participation.

I've learned a lot in the past few months about Linux and various pieces-parts of putting all my disparate gear together to make a system. Adding automated SDR with WeFax capability is definitely attractive to me as we get closer to our estimate Q3-2023 cruising departure. Plus, it's cheap by comparison, so why not do it if it can be done?

Onward...
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Old 16-04-2021, 14:31   #12
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Re: Weatherfax and SDR

I guess receiving weatherfax would be one good reason to start using RPI.
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Old 16-04-2021, 15:38   #13
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Re: Weatherfax and SDR

Quote:
Originally Posted by SCarns View Post
Another reason to look for a different dongle. I’ll mess around with this some more later.
You can use the old dongles as an AIS receiver, or with a little app called rtl-433 you can decode most things transmitting on 433 mhz, like some wind instruments do.
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Old 16-04-2021, 17:14   #14
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Weatherfax and SDR

I package all Ham and SDR software and marine protocols decoders for raspberry pi in a single image.

https://github.com/bareboat-necessities/lysmarine_gen

There is NavTex, WeatherFax, Satellite NOAA weather, Inmarsat Fleet decoders (JNX, JWX, noaa-apt, ScyTale-C)
as well as pat WinLink client

All free open source.

I hope someone can pick it up and make it work with SDR. I’d love to add it into HowTo section of the documentation.

I didn’t have time to test these features myself.
I have miniwhip PA0RDT by Rohloff Baker antenna for NavTex and SDR but I haven’t bought upconverter.

thanks
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