Idea that was rolling around in my head.. What if you had two identical SW radios, lets say radio A and radio B. 'A' tuned to the station you want to hear that isn't picking up so well because of bad band conditions or RFI, and 'B' tuned to static (no station) right next to the received channel. Then take radio B and flip the phase of it's audio output and then finally sum its audio with radio A so that both are heard minus the static or natural interference.
My idea here is that being the static on B is so close to frequency of the station being picked up on A, and that the audio phase is being flipped it will cancel out any static being heard from the station you want to hear.
This idea stemmed from some thinking of how karaoke vocal removers work. They take the left or right channel and phase flip it, then add left+right to mono and if vocals are directly center of left or right on the CD it mostly will remove it.
I have no idea if that would work for removing static on radio, but just a thought
If you guys don't tell me this won't work for some obvious reason I may just try it when I get the chance just out of curiosity to see what happens, even if it doesn't work.
Only difficulty I see with this is the proper amplitude of each noise spike being maintained between frequency A and frequency B while maintaining the overall level of the mix-minus signal to null the noise spikes.
Why not just split the signal after the detector, invert one of the paths, then combine into a summing amp using just one radio? Build the circuit so that it detects peaks above a certain threshold and time domain so as to not confuse wanted audio and null that out.
Basically hi end radios have noise suppression circuitry that works on this principle with the exception of utilizing a mix-minus approach. They simply gate the noise spikes down to a low level considerably lower than the amplitude of the wanted sound. Works pretty good!
Peace!
K-ROCKS RadioOne
ZeroPointRadio
AM Stereo 1670
FM Stereo 92.1
Basically what a noise blanker does. Except here you are doing it at audio (very inefficient) and a noise blanker does it in the IF.
Pulse width and phase are very important in noise cancelling. Why it's done as early as possible in the receiver (TV's are different matter, where it's done at video level with syncing and gating).
There's an RF method that effective for local QRM, that has a loop and a vertical and a phase box. I think it's in the ARRL handbook?
Post by HighMountainRadio on Jan 13, 2018 19:50:16 GMT -6
Greetings Kage !
At first glance I thought you were referring to 'dual diversity' receiver setup.. After reading more thoroughly, sounds to me like you are describing the concept behind the Bose Noise Cancelling Headphones.. Nice idea, any progress ?
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