4 ms·

Beeps and melodies in two-way radio

57 points by sasvari 8y ago

th0ma5 8y ago
Every time she posts I feel simultaneously excited of what's to find in there, and dumber because I haven't gone this deep into something. Such great writing where the subject matter is both compelling and the author has done their homework.
- tonyarkles 8y ago
  Yeah, she is undoubtedly an inspiration for me! Really awesome explorations of interesting things.
  - squarefoot 8y ago
    Not to mention her site is a lesson on how to make articles easily readable. From the use of greys to text and links colors, the lack of too light images and the barely noticeable background pattern: everything on that page is gentle to the eyes. This is how web pages should be designed. Thanks!
Aloha 8y ago
This mostly seem to center around someone doing analysis of a FRS like radio service. Generally professional radios don't send roger beeps over there air. Not have I ever heard of "STE" - and certainly not as the method described, normally you'd change the phase of the CTCSS tone by 120 degrees, which is the signal to the radio that the transmission ended. The phase reversal method was used because of the amount of time it took vibrasponder reeds to stop vibrating, but changing the phase you could end the vibration faster.
- interfixus 8y ago
  Not "someone". Oona Räisänen, consistently fascinating writer on all things rf, and orders of magnitude deeper into her fields than I could ever even imagine myself into anything.
  - Aloha 8y ago
    She may be fascinating, that does not make her technically correct, nor an expert in this field.
bobowzki 8y ago
The 1:20 decimation could probably be done more efficiently with CIC filter, I would look into that. Love the terminal user interface! I would like to write something like that for a shortwave raspberry pi transceiver we are building, http://tujasdr.com http://tujasdr.com.
zackmorris 8y ago
This is the most concise explanation of Gaussian peak interpolation from the article that I can find. Unfortunately it's a pdf, but it does have a full example: http://www.add.ece.ufl.edu/4511/references/ImprovingFFTResoltuion.pdf http://www.add.ece.ufl.edu/4511/references/ImprovingFFTResol... RFFT_SIZE = 256 magAddr: points to array of FFT magnitude results sample_freq = 8000Hz TI_FFT(): TI optimized function to calculate FFT maxidx_SP_RV_2(): TI optimized function to find maximum value in array TI_FFT(); //perform TI FFT analysis. int max_bin = maxidx_SP_RV_2(magAddr, RFFT_SIZE>>1); //find max bin float freq_rez = (float)sample_freq/RFFT_SIZE; //calculate frequency resolution float inter_bin = max_bin + log(magAddr[max_bin+1]/magAddr[max_bin-1])*0.5 /log(magAddr[max_bin]*magAddr[max_bin]/(magAddr[max_bin+1]*magAddr[max_bin-1])); //calculate the intermittent bin on continuous spectrum using GI freq = (unsigned)(freq_rez*inter_bin); //calculate max input frequency I believe that the above is C code, so the array indices are 0-based. I can't find anything on TI_FFT except a bunch of PowerPoints, so you'll probably want to use a better documented FFT function: https://www.google.com/search?q=TI_FFT&tbs=li:1 https://www.google.com/search?q=TI_FFT&tbs=li:1 Here is the maxidx_SP_RV_2() function: http://read.pudn.com/downloads543/sourcecode/embedded/2242363/C28x_FPU_LIB/maxidx_SP_RV_2.asm__.htm http://read.pudn.com/downloads543/sourcecode/embedded/224236...
4FNET7 8y ago
You would enjoy hackgreen. The displacement fields end up generating a sequence over nuclear reticules so you get a signal into the wire and that pletes into your own over some ranged wifi or something and you can literally find yourself in a wide band screener for free. Ecosia search for hackgreen. It's bad ass.

57 points by sasvari 8y ago

Every time she posts I feel simultaneously excited of what's to find in there, and dumber because I haven't gone this deep into something. Such great writing where the subject matter is both compelling and the author has done their homework.

tonyarkles 8y ago
Yeah, she is undoubtedly an inspiration for me! Really awesome explorations of interesting things.
- squarefoot 8y ago
  Not to mention her site is a lesson on how to make articles easily readable. From the use of greys to text and links colors, the lack of too light images and the barely noticeable background pattern: everything on that page is gentle to the eyes. This is how web pages should be designed. Thanks!

Aloha 8y ago

This mostly seem to center around someone doing analysis of a FRS like radio service. Generally professional radios don't send roger beeps over there air. Not have I ever heard of "STE" - and certainly not as the method described, normally you'd change the phase of the CTCSS tone by 120 degrees, which is the signal to the radio that the transmission ended. The phase reversal method was used because of the amount of time it took vibrasponder reeds to stop vibrating, but changing the phase you could end the vibration faster.

interfixus 8y ago
Not "someone". Oona Räisänen, consistently fascinating writer on all things rf, and orders of magnitude deeper into her fields than I could ever even imagine myself into anything.
- Aloha 8y ago
  She may be fascinating, that does not make her technically correct, nor an expert in this field.

bobowzki 8y ago

The 1:20 decimation could probably be done more efficiently with CIC filter, I would look into that. Love the terminal user interface! I would like to write something like that for a shortwave raspberry pi transceiver we are building, http://tujasdr.com http://tujasdr.com.

zackmorris 8y ago

This is the most concise explanation of Gaussian peak interpolation from the article that I can find. Unfortunately it's a pdf, but it does have a full example: http://www.add.ece.ufl.edu/4511/references/ImprovingFFTResoltuion.pdf http://www.add.ece.ufl.edu/4511/references/ImprovingFFTResol... RFFT_SIZE = 256 magAddr: points to array of FFT magnitude results sample_freq = 8000Hz TI_FFT(): TI optimized function to calculate FFT maxidx_SP_RV_2(): TI optimized function to find maximum value in array TI_FFT(); //perform TI FFT analysis. int max_bin = maxidx_SP_RV_2(magAddr, RFFT_SIZE>>1); //find max bin float freq_rez = (float)sample_freq/RFFT_SIZE; //calculate frequency resolution float inter_bin = max_bin + log(magAddr[max_bin+1]/magAddr[max_bin-1])*0.5 /log(magAddr[max_bin]*magAddr[max_bin]/(magAddr[max_bin+1]*magAddr[max_bin-1])); //calculate the intermittent bin on continuous spectrum using GI freq = (unsigned)(freq_rez*inter_bin); //calculate max input frequency I believe that the above is C code, so the array indices are 0-based. I can't find anything on TI_FFT except a bunch of PowerPoints, so you'll probably want to use a better documented FFT function: https://www.google.com/search?q=TI_FFT&tbs=li:1 https://www.google.com/search?q=TI_FFT&tbs=li:1 Here is the maxidx_SP_RV_2() function: http://read.pudn.com/downloads543/sourcecode/embedded/2242363/C28x_FPU_LIB/maxidx_SP_RV_2.asm__.htm http://read.pudn.com/downloads543/sourcecode/embedded/224236...

4FNET7 8y ago

You would enjoy hackgreen. The displacement fields end up generating a sequence over nuclear reticules so you get a signal into the wire and that pletes into your own over some ranged wifi or something and you can literally find yourself in a wide band screener for free. Ecosia search for hackgreen. It's bad ass.