set MyFiles=*.flac *.fla *.wav *.aif *.mp4 *.mp3 *.mp2 *.aac *.ogg *.m4a
for %%a in (%MyFiles%) do ffmpeg -i "%%a" -y -lavfi showspectrumpic=s=1920x1080:color=fiery:gain=.7:fscale=lin:orientation=0:saturation=1:mode=combined:legend=enabled:start=0:stop=8000 "%%~na.jpg"

https://swradiogram.net/post/733945139549126656/shortwave-radiogram-17-20-november-2023-program

Shortwave Radiogram transmits digital text and images on an analog shortwave broadcast transmitter. The program is produced and presented by Dr. Kim Andrew Elliott.

• Shortwave Radiogram, 17-20 November 2023 (program 330): Another EasyDRF Special

  The next Shortwave Radiogram will be another EasyDRF special produced by Daz Man in Australia. EasyDRF is a Windows application program for sending files over radio using HamDRM format. EasyDRF is somewhat complex and less tolerant of difficult reception conditions than our MFSK and other digital modes. But when it works, the results are dazzling.
  
  Our previous EasyDRF special was 11-16 May 2023.
  
  Daz Man’s instructions for the EasyDRF are below. Please take the time to read them. Note that Daz provides a link to an audio file, so that you can practice decoding EasyDRF before the actual broadcasts begin.
   

=======>     http://www.rhci-online.net/html/SWRG-330/SWRG-330-00.html

Daz Man’s guide to decoding the Shortwave Radiogram EasyDRF special

Questions about EasyDRF can be addressed to Daz via Twitter: @DazDude4000, or email: dazdude(at)hotmail.com

Quick start:

* Download EasyDRF.exe here: https://github.com/DazDSP/EasyDRF/tree/master/Release

* Installation info is here (yellow text): https://dazdsp.org/tech/EasyDRF/index.html#install

* Setup info is here (cyan text): https://dazdsp.org/tech/EasyDRF/index.html#setup

The audio from this file can be used for practice decoding: https://storage.googleapis.com/dazman/misc/SWRG-330-v1-WINB.wav

Common mistakes:

* Using AM envelope detection degrades performance - Standard AM detectors generate distortion when the carrier fades, resulting in loss of OFDM data. Always use AM-Sync or SSB detection for best results on AM broadcasts. Using SSB instead of AM-Sync may cost 3dB of SNR.

* IF filter too narrow - Cutting sidebands of the OFDM data will cause data loss.

* Mistuned SSB - The default EasyDRF search window is only 5Hz. Excess tuning error will prevent decoding.

* Edge browser can’t display the images. Use Firefox or Chrome.

Details:

The EasyDRF Radiogram program sends the entire program as a series of files using the EasyDRF Windows application program. The EasyDRF Radiogram broadcast text is sent as HTML, and the HTML loads the images automatically.

The “Rx Files” button on EasyDRF allows easy access to the folder where the files are saved.

The first file to be sent in the broadcast is the HTML. Open the HTML in the Rx Files folder with a web browser using the standard Windows methods like drag-and-drop, or File->Open etc. The HTML file must remain in the Rx Files folder during decoding, so it can load the images and stats data.

When the HTML is displayed in a browser, watch and wait as the images decode and load into the page. SNR stats data is displayed for the decoding, to evaluate reception quality.

The EasyDRF executable is available on GitHub:

https://github.com/DazDSP/EasyDRF/tree/master/Release

The EasyDRF web page is here:

https://dazdsp.org/tech/EasyDRF/

For analog radios:

Feed the audio into the PC from your analog receiver via a sound device line input. Select the line input on the EasyDRF Soundcard menu, RX Input setting. The peak input level should be around -6dBFS to -12dBFS.

For SDRs:

Feed the SDR output to EasyDRF using a Virtual Audio Cable (VAC - VB Cable is suitable). Set the SDR audio output or PC default sound output to the VAC input, and select the VAC output in the EasyDRF Soundcard menu, RX Input setting.

EasyDRF uses OFDM. OFDM is wider bandwidth than MFSK64 and requires more SNR to decode. The EasyDRF signal extends from about 350Hz to 2850Hz. The receiver passband should be slightly wider than this.

This means the AM RF bandwidth will need to be at least 6kHz. If the receiver bandwidth is too narrow it can cause decoding failure.

Use AM-Sync mode for demodulating the AM broadcasts. Standard AM envelope detectors distort on carrier fades, which causes data loss on the EasyDRF OFDM signal.

If using SDR# (SDR Sharp), select DSB + Lock Carrier for AM Sync mode. IMPORTANT: DISABLE SDR# ANTIFADING, as it badly damages the OFDM data.

If using HDSDR, use ECSS mode with both sidebands. If there is severe Doppler (rapid fading) use ECSL or ECSU (single sideband sync mode), or SSB mode.

If AM-Sync is not available, use SSB mode. The SSB passband should be at least from 300Hz to 2900Hz. Some amateur transceivers may have an IF filter that is too narrow, which will cause decoding failure.

In SSB mode the tuning MUST be accurate to within 5Hz, or decoding will fail. The three EasyDRF OFDM pilot tones should be located in the centre of the red bars at the top of the EasyDRF waterfall display. For a drifty SSB receiver the search window width can be set wider in RX Settings, but EasyDRF will not remember this setting after closing the app. Setting a wider search window may degrade the data decoding reliability in some cases.

Try to pick the best time and frequency broadcast for your area. If the signal is in the noise, or is suffering extreme Doppler shift it is unlikely to decode.

If MFSK images on your setup suffer from image jumps or glitches, this indicates the SDR or computer system is dropping audio data. This will cause data loss on the EasyDRF decoding, increasing the chance of decoding failures. The EasyDRF RS4 error correction needs more than 51% good data to decode, which allows an error margin of as much as 49% in most cases (this varies with the fading pattern).

It is a good idea to record the broadcast in case of decoding problems. An IQ recording from an SDR is the most flexible, as it allows tuning and modes to be changed during playback. If that is not possible, an audio recording will do.

The HTML page displays SNR stats on the reception quality. Please include the stats with your reports.

Decodes from multiple broadcasts can be combined if needed - but this will make the SNR stats data inaccurate.

If you want to try decoding more than one of the EasyDRF broadcasts, the previously saved files should be moved from the Rx Files folder to another folder. If this is not done, the HTML image loading will automatically stop if all the files are already present. Don’t forget to also move the “.js” stats data file that contains the SNR data for each particular decode attempt.

Before decoding a different broadcast of the same program, the EasyDRF application should be closed and restarted to clear it’s memory cache. Otherwise it may refuse to decode the same files again, as they have already been saved.

Daz