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Updated Audio Receivers (markdown)

Brumi-2021 2024-03-10 11:47:30 +01:00
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Audio-Receivers.md

@ -55,7 +55,7 @@ The Key Items on the App that can be seen or selected with the cursor and change
The next item is the setting of the bin sizes used for the waterfall (0-63) with “0” being the minimum information being the fastest display and “63” the maximum information collected the slowest display. Adjust to give a balance of speed and information seen.
And next right to that field ,while you are still in SPEC mode, you will see the Rx_IQ_CAL field. It actually can improve (8 to 10 dB's from worse CAL point to the best one ) the receiver Image Reject Ratio (IMRR) only in the Receiver Applications that are using Zero IF-frequency tuning ,like this SPECTRUM mode. This calibrated value will be stored in the SD card , /settings/rx_audio.ini .
And next right to that field ,while you are still in SPEC mode, you will see the Rx_IQ_CAL field. It actually can improve (8 to 10 dB's from worse CAL point to the best one ) the receiver Image Reject Ratio (IRR) only in the Receiver Applications that are using Zero IF-frequency tuning ,like this SPECTRUM mode. This calibrated value will be stored in the SD card , /settings/rx_audio.ini .
To calibrate it , you will need to try to find some clean isolated continuous air carrier signal (please make sure that it is a real air signal, not internal harmonic residual interference clock beats) , and try to tune it , (for example, to the right of the positive frequencies ). Select properly the SPEC BW to try to isolate that air carrier signal (in below example , I selected BW = 2 Mhz).
Then, to make slightly more visible the bare Image mirror frequency -that appears in the other symetric left part screen.-, you will need to start set up CAL to 0 (min). Then , you will need to adjust AMP , LNA and GAIN to receive strong enough signal to the right part (but at the same time , not so strong to not produce intermodulations , otherwise re-adjust again decreasing AMP, LNA, GAIN) , and not so weak , till just getting the carrier +freq. clean (desired carrier signal) , and its bare visible Image mirror Signal (in the other symetrical -xx mirror freq . (unwanted Image signal to be minimized) . Then, when you got similar situation as left below picture, you can start adjusting Rx IQ phase CAL till minimizing the received Image "mirror" signal (as in the middle below picture).