Re: Continuum mode


Heh heh - processing in the frequency domain makes a lot of this easy. The chief issue is the current FFT resolution compared the bandwidth you want. The "cheap, quick, and dirty" solution is sum the power in all the bins within the bandwidth you want. I suspect using some shaping on that would add a decimal place to the accuracy as well as more processing demand on the system.

Now, if you use receivers as the filtering mechanism running a reverse FFT on that bandwidth (and a little bit more which will be super close to zero power and gives a power of two number of FFT steps) gives you time domain I and Q signals. And, I wish SDRC did this so its S in its SINAD fiddling would not be spoofable, square I, square Q, sum them together, and take 10 log that power equivalent. That gives the continuum measurement as well as a very good S for calculating SINAD ratios. (As Simon curls up in a corner screaming "I didn't read that! I don't wanna do it!")

(Snarky today Joanne? Yeah, just had the telephone guy come to deal with noisy phone lines when it gets windy. It was still air. So, in another half hour the internet vanishes here as the afternoon winds kick up. This time it's war. A couple days ago the noise made a telephone consult with my doctor a miserable series of "say again" and CRACKLE! CRACKLE! CRACKLE!)


On 20220316 08:33:43, sm6fhz wrote:

I would like to add two more points to the short spec for the Continuum Mode function:

  • Possibility to set a smaller BW for the measurement than the sampled BW and to set where this BW shall be in frequency (within the sampled range).
  • The cursor (when moved into the plot) to show the actual indicated value at it's position in the graph. Where it shall show can be discussed, but close to the cursor would be one possibility. There are probably many alternatives where to show the number.
This is because with the now available very broad band SDR's (e.g. RX888 etc.) it might be impractical or undesirable to measure over the entire sampled BW due to spurious signals, unwanted signals or other limitations.
The cursor reading has earlier proven to be a very practical feature when using Continuum Mode.
I hope these are feasible functions to implement.

73 / Ingolf, SM6FHZ

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