TheArchive/mayhem-firmware
1
0
Fork 0
mirror of https://github.com/portapack-mayhem/mayhem-firmware.git synced 2025-11-14 12:45:17 +00:00
Code Issues Packages Projects Releases Wiki Activity

Updated Audio Receivers (markdown)

gullradriel
2025-04-14 21:25:12 +02:00
parent ead36925ad
commit 5b2942e07e
1 changed files with 4 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
Audio-Receivers.md

@@ -52,13 +52,13 @@ The Key Items on the App that can be seen or selected with the cursor and change
* **USB+FM:** It is usually used to demodulate Wefax (HF Weather fax transmissions) , demodulating the signal in two steps, first demodulating the tuned RF signal in USB , extracting audio tones. And then demodulating again those FM modulated subcarrier audio tones, to extract APT low scan weather fax map signal. (that signal can be recorded into audio.wav file ).
For a correct demodulation ,currently we need to tune that published frequency , (in our application , you do not need to apply any usual - 1.900Khz offset . The -tuning offset , is already applied internally). So we have to just tune the (published) Wefax Station frequency directly .
* **Record button:** press to record a file
* **Record button:** press to record a file, press one more time to stop the record.
* **Marker Frequency** Just below REC Icon we have a marker Frequency field input (0 Hz) , that we can adjust from 0..48kHz range with the knob rotary encoder, with 200 Hz step jumps. It will move a short vertical red line pointer cursor across the Multiplex FM demodulated baseband FFT spectrum graphic. It could be useful to see and confirm the exact frequency of those spectrum peaks, like the below picture , showing 19Khz pilot carrier tone from a usual Stereo FM Broadcasting.
* **Marker Frequency** Just below REC Icon we have a marker Frequency field input (0 Hz) , that we can adjust from 0..48kHz range with the knob rotary encoder, with 200 Hz step jumps. It will move a short vertical red line pointer cursor across the Multiplex FM demodulated baseband FFT spectrum graphic. It could be useful to see and confirm the exact frequency of those spectrum peaks, like the below picture , showing 19Khz pilot carrier tone from a usual Stereo FM Broadcasting.
* **Waveform display** if you get down the marker frequency and put focus on the wafeform display, you can disable it with a single click
* **Waveform display** if you get down the marker frequency and put focus on the wafeform display, you can disable it with a single click
* **Frequency shit** if you get down the Waveform display or just touch the screen, you'll enter in the frequency shift mode. A flashing red dot will indicate the next position. Use rotary encoder or click on the screen, and press enter to set the new frequency.
* **Frequency shit** if you get down the Waveform display or just touch the screen, you'll enter in the frequency shift mode. A flashing red dot will indicate the next position. Use rotary encoder or click on the screen, and press enter to set the new frequency.
Note : All AM modes (DSB 9K, DSB 6K, USB ,LSB, CW) and AMFM mode has the option to expand x2 , the waterfall , selecting ZOOM x1/ZOOM x2
@@ -83,8 +83,6 @@ Here in that Audio App we can tune , and RECORD the APT signal into file.wav ,ma
> ![image](https://github.com/portapack-mayhem/mayhem-firmware/assets/86470699/88ef7389-d7c0-47a8-84ed-05d836879af5)
* **SPEC.** The spectrum Secondary Items allows the view of the RF spectrum with different setting for maximum bandwidth shown:
20M with markers at +/- 5M
@@ -105,8 +103,6 @@ That below example is calibrating H2+ old r6 version (max2837) that has 31 steps
![image](https://github.com/portapack-mayhem/mayhem-firmware/assets/86470699/84dc2b51-e265-40aa-a0b8-fb8d9270e6b3)
* **CTCSS:** This Continuous Tone Coded Squelch System is a display at the end of the secondary information line. It is used by many systems and standardised by EIA/TIA, with a description [here.](https://en.wikipedia.org/wiki/Continuous_Tone-Coded_Squelch_System ) In the NFM mode in Audio app, the tone field is increased from 11 to 14 characters.
Now , the CTCSS tone frequency and CTCSS code numbers are displayed at once (if a matching freq was found in the tone_key table). See the Annex to this document below. It should be noted that most of the time the display is jumping around and only clearly displays the received tone when there is a gap in the voice and the Signal is of good quality.