RTL-SDR Decoding ALERT

1

Hi,
I am trying to get the following project going to decode a flood warning ALERT Protocol using an RTL-SDR. GitHub - cparker/udfc-node: Node.js code for filtering data gathered from nearby weather stations into JSON - SignalsEverywhere: Investigating USGS Gaging Stations and their GOES Satellite Connection
I was wondering if anyone has experience with Minimodem and the RTL-SDR and could help me with the decoding. I have got it to a point where I can see data, but it is decoding incorrectly.

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Hey @Adam17419, Welcome back to the forums!

Unfortunately, I don’t have much experience at all with Minimodem or RTL-SDR, I would offer some resources but it seems you already have some good ones!

Perhaps one of our active forums members will have done something similar before. Curious to see!

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Check the baud rate of the ALERT protocol you’re decoding (e.g., 300 baud for some weather station signals). Use the -r flag in Minimodem to specify the rate, e.g., minimodem -r 300.

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Thanks @lia262073 I’ve been using 300 baud, but i have not had any luck unfortunately. I will keep persevering.

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Hey @Adam17419,

The SignalsEverywhere link you provided references another project written in Python to do this kind of thing:

Have you looked into this at all? Depending on how far down the udfc-node rabbit hole you have gone, and your specific requirements this could potentially be an easier option for achieving this?

Hope this helps! :slight_smile:

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Thanks Samuel. GOES-R is a different transmission type and a different message protocol to what I am trying to decode.

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Hi,

As the BoM (& other gauge owners) don’t make M2M data available (unless $$$, and even then …), it would be great to be able to receive the gauges directly (BoM 151.5MHz, others ?)

Now that the BoM is going over to ALERT2 (4800 baud, GNSS-sync’d TDMA), has anyone got decoding for that working?

Does anyone even have decent documentation on the local implementation? My searcheing to date suggests that it’s all a fairly well-kept secret.

(BTW: They used CCITT modulation for the Aust implementation of ALERT1)

Here are a few links I found with some helpful info here (but fairly scant):

https://www.hydrologicwarning.org/content.aspx?page_id=22&club_id=617218&module_id=160407

https://www.bom.gov.au/water/standards/documents/Consultation_feedback_log_and_response.pdf

https://elprotech.com/wp-content/uploads/2024/12/Alert-2-Introduction-BH-V1.pdf

Keen to hear if anyone wants to collaborate on this.

73

Greg

VK2GTH

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