The RS41 just uses regular ol' FSK, so we don't need to worry about this theoretical communication engineering stuff. Increasing the symbol count increases the channel capacity, but comes at a cost, which is not to be discussed here. FSK-4 uses 4 symbols, each representing two bits. In this case, every symbol encodes a single bit. In it's most simple form, FSK-2 (or just FSK) there are just two frequencies and thus symbols. Through switching between the different frequencies (keying them) a data stream can be sent. So what is FSK exactly? FSK is a way of sending data, in which every symbol is transmitted by sending out a certain frequency representing that symbol. This is also what differentiates Narrow-Band-FM (NFM) from Wide-Band-FM (FM) and why you have to set your receiver to NFM to be able to decode radiosondes. The actual frequency deviation of the carrier is specific for each transmission standard and has to be selected (to some degree) in accordance to the signals bandwith. The frequency of the signal is determined by how often the it's amplitude changes polarity, and this is why the speed at which the carrier's frequency changes represents the frequency of the signal. The actual frequency of the carrier is a way of transmitting the amplitude of the signal. Note that not the actual frequency of the carrier at any given moment encodes the frequency of the signal, but rather the gradual change of frequency over time. With FM-Modulation, an analog signal (usually audio) is transmitted by varying the carriers frequency accordingly. However, I would like to add a simple PoC-style decoder, most likely as a C++ WPF application, at some point.įor a more detailed explanation, refer to Wikipedia.Īt it's core, FSK (Frequency Shift Keying) just is binary FM-Modulation.
#Nemo analyzer nfm data format how to
There is no actual decoder in this repo, just the knowledge on how to build one. Detailed explanations on the different RS41 models can be found in the appropiate files/folders. Then I will talk about the general Frame structure. My findings are really nothing new, at the end this repo is, for the most part, just an extended documentation of Zilog80s decoder, to whom most of the kudos belong.įirst I will explain a little how FSK Modulation works an how we can obtain the raw bytes sent. obtain and analyze data from 1.68 GHz RS41-D.obtain and analyze data from RS41-SGMs radio silence mode.add information on xdata other than for regular ozone soundings.find out purpose of various bytes in the STATUS and MEAS Blocks.This repositories purpose is to explain how the radiosonde Vaisala RS41 transmitts it's data to the ground station, how third parties can obtain the data as well as decode and interpret it.įor general information about radiosondes check out Wikipedia.įor more information about the RS41 check out my website.Ĭorrections and additions are always welcome, just fork the repo, edit accordingly and file a merge request.
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