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Updated Capture (markdown)

Mark Thompson 2023-12-17 11:07:40 -06:00
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Capture.md

@ -12,7 +12,7 @@ The Key Items on the App that can be selected with the cursor and changed with t
* **Step Size:** The selected step size of frequency adjustment carried out by the Rotary encoder. * **Step Size:** The selected step size of frequency adjustment carried out by the Rotary encoder.
* **Gain:** Amp (0dB or 14dB), LNA(IF) (0-40),VGA(Baseband)(0-62) * **Gain:** Amp (0dB or 14dB), LNA(IF) (0-40),VGA(Baseband)(0-62)
* **Rate:** The sample rate, which by its nature set the set bandwidth of capture. This is shown in the markers around the centre line of the waterfall display. The sample rate is variable from 12k5 to 2750K (*) in many steps. You need to ensure that the sample rate is more than twice the bandwidth of the signal you want to capture see [(Nyquist Principle / also called Shannon’s Law) ](https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem) * **Rate:** The sample rate, which by its nature set the set bandwidth of capture. This is shown in the markers around the centre line of the waterfall display. The sample rate is variable from 12k5 to 2750K (*) in many steps. You need to ensure that the sample rate is more than twice the bandwidth of the signal you want to capture see [(Nyquist Principle / also called Shannon’s Law) ](https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem)
* **Format:** The user can select two file formats, of the recorded IQ data 16 / 8 bits : C16 (complex 16) or C8 (complex 8), and its related file extension ".C16" or "C8". (By default we are preselecting C16). * **Format:** The user can select two file formats, of the recorded IQ data 16 / 8 bits : C16 (complex 16) or C8 (complex 8), and its related file extension ".C16" or "C8". (By default we are preselecting [C16](https://github.com/eried/portapack-mayhem/wiki/C16-format)).
* **Trim:** If checked, the capture will attempt to be automatically trimmed to only contain the signal part. This is not reversable. Consider using the IQ Trim utility instead if you're not sure you can capture the signal again. * **Trim:** If checked, the capture will attempt to be automatically trimmed to only contain the signal part. This is not reversable. Consider using the IQ Trim utility instead if you're not sure you can capture the signal again.
Note (*) : Currently , **for correct reliable Replay application ,you should ONLY use Capture App selecting any Bandwidth capture <= 1Mhz (but 500Khz is the recommended for majority micro SD cards compatibility because it requires a quite common average write speed in our system >2MB/sec,C16)**. From 600khz till 1Mhz (and 1.25 MHz) , you will need more fast and good quality micro SD card (with min average write speed in our system >3MB/sec (for BW=750khz,C16) , and >4MB/sec (for BW=1Mhz ,C16), (>5MB/sec for BW=1.25Mhz ,C16) and with as small as possible write random latency. (In the GUI , those correct bandwidth capture options appear with the Normal usual "REC" icon Background color, as user recommended BW capture options). If you face too much % dropped samples when recording , you can retry it reducing C16 to C8 , that also reduces the needed average write speed :2 (example 1Mhz rec will need average sd interface speed of 4MB/sec in C16 or 2MB/sec in C8). Note (*) : Currently , **for correct reliable Replay application ,you should ONLY use Capture App selecting any Bandwidth capture <= 1Mhz (but 500Khz is the recommended for majority micro SD cards compatibility because it requires a quite common average write speed in our system >2MB/sec,C16)**. From 600khz till 1Mhz (and 1.25 MHz) , you will need more fast and good quality micro SD card (with min average write speed in our system >3MB/sec (for BW=750khz,C16) , and >4MB/sec (for BW=1Mhz ,C16), (>5MB/sec for BW=1.25Mhz ,C16) and with as small as possible write random latency. (In the GUI , those correct bandwidth capture options appear with the Normal usual "REC" icon Background color, as user recommended BW capture options). If you face too much % dropped samples when recording , you can retry it reducing C16 to C8 , that also reduces the needed average write speed :2 (example 1Mhz rec will need average sd interface speed of 4MB/sec in C16 or 2MB/sec in C8).