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We made QAM64 modes that transmit at almost 4Kbit/s with a 1/2-rate FEC code (8Kbit/s raw): github.com/aicodix/modem/tree/next

@@xdsopl that's really interesting - I've been playing with voice (highly compressed, codec2 at 450) and small scale data (telemetry, position reports, messages) over LoRa and GMSK on VHF & UHF - but if your modem can do that kind of speed with 50% FEC overhead I probably should start looking in that direction. One thing I did like about LoRa was its ability to work at levels well below the noise floor, but it has numerous cons too. Treating any voice as "near real time" has also been instrumental in getting things to work when relayed through, for example two other stations. Ultimately my plan is to have a mix of RF repeating (preferably on a second VFO) and internet routing, so the network may be degraded in speed but remains useful in a power out scenario. Authentication/message signing is something I'd also like to see at least for sensitive operations like telecommands to repeaters etc but that's a future desire, and I'm still in the "is there a better radio I can use" stage. 73 and great work on the modem and the sstv like and text like PoCs

@@manyshnooks LoRa (et al) struggle with multipath. For voice you could use a BCH code and OSD per OFDM symbol to lower the latency. Did some experimenting with Ed25519 for authentication: github.com/xdsopl/ed25519_blake2b

@@xdsopl hah I was going down the same route given the efficiency of EC. And yes, absolutely re LoRa, it is the wrong tool for the job.

@@manyshnooks LoRa works really well for ultra low power and is very easy to generate _and_ demodulate. But nowadays we have crazy amounts of transistors .. better to start using them.

Yup, tried to encapsulate as much as I could. Still need to make the main function smaller though.

Assempix is for decoding only. If you want to send pictures, you need Shredpix for encoding: www.aicodix.de/cofdmtv/shredpix/

​@xdsopl he means shredpix

@@pomni_tadc_real Either there is a problem with the picture file format or the concept of sharing a picture from the picture gallery is

​@xdsopl fix it so an looking like select image no file chosen

@@pomni_tadc_real I can only fix problems I can reproduce. Please send me the problematic image.

If you have a device with two microphones, you can select which one to use. Sometimes just using Default will do some counterproductive extra audio processing, even though you have chosen Unprocessed in Audio Source. Then choosing either First or Second from the Channel Select menu will help you to improve the audio signal. There really is no way to figure these settings out in a programmatic way, so you have to play with those settings until you find the one that works best.

My pleasure. AFAIK ADS-B needs a much larger bandwidth (2 MHz) than voice (3 kHz). So using a higher bandwidth receiver like a RTL-SDR for example is necessary. Playing with ADS-B is on my bucket list.

@xdsopl I really don't know how this works, however..the quansheng UV-K5(8) radio that costs only $15 can be unlocked to receive on a frequency between 15khz to 1300mhz, again..not sure how it works but couldn't the signals received for AIS and ADS-B be decoded somehow only through audio?

​@@ExploringWithJason I don't know if it can provide the 25kHz bandwidth necessary to receive AIS but ADS-B is out of the question with a voice receiver. You really need a higher bandwidth receiver with these signals. Just being able to tune to the right carrier is not enough, you also need the bandwidth at that frequency. RTL-SDR dongles are really cheap and there are smartphone apps that decode these signals via an OTG cable.

@@xdsopl oh, I know, I have an rtl-sdr V4 and I have SDRAngel and dump1090 installed on my android phone, but facinated about what those little quansgeng's can do 😅

I've just released Assempix v1.13 as open beta and it might take some time until you can install it from the Play Store. Shredpix does not have this feature yet and you need to use the command line modem and the CRS tool to create chunked transmissions.

We developed the #Rattlegram app on Android first and after many requests, we ported it to iOS too. #Rattlegram can now be found on both app stores.

Cool, that explains the recent uptick in download numbers. Very happy to hear about it. Have fun with the apps!

That's the spirit! Satellites usually use much simpler signals, as they don't have to deal with multipath (or echo) but rather with the Doppler effect if they are non-stationary and with distortion caused by non-linear but efficient RF amplifiers. You can either contact me directly or watch some of the videos about #OFDM (Orthogonal Frequency Division Multiplexing) and #FEC (Forward Error Correction) if you are interested in this subject.

I don't know how easy it is to get another SSTV app on the Apple App Store, while there is one already. I was thinking to maybe try that if I get motivated enough to rewrite Robot36 and make it multi-platform, as Renderscript has been deprecated ..

@@xdsopl I don't use Apple, so I'm not familiar with their app store offerings. Last you and I had talked, you were moving development of Ribbit/Rattlegram from Android to Apple. This is the second video I've seen of a better looking SSTV decoder app though, and I'm curious what it is.

@@coreymckay4433 It's Assempix, available on the Google Play Store. You can use Shredpix to send pictures digitally over audio, which can be decoded by Assempix. Unfortunately they have not taken off as much as Rattlegram has, so I've decided to focus my efforts into the next multi-platform app, which does file transmission.

@@xdsopl I completely forgot about those, I'll experiment with those. Those use OFDM as well, correct?

@@coreymckay4433 Yes, same procedure as every year 🥰

Yeah, that's me

I agree that messaging these days leaves much to be desired when it comes to something a simple as writing to a small group as fast and hassle free as possible

Eventually. Right now I would like to focus on the next app. Have you seen the port of Rattlegram to Rust/WASM by @bastibl yet?

@@xdsopl no I have not

Yeah, I made this as a meme. It is totally impractical to send a #QAM256 modulated signal over the air. I just barely managed to send data over a loudspeaker and a microphone where both are so close that they are almost touching. If you want to try this kind of technology yourself, search for Rattlegram on either the Apple App Store or Google Play Store. It is free!

The code for the new #QAM16 modes can be found here: github.com/aicodix/modem/tree/next

Made three new meme #QAM256 modes, just for you @ArclampSDR ! This way you can send up to 680 bytes in a second, if the channel allows it: github.com/aicodix/modem/tree/silly

I think I am gonna add a couple of comb type pilots to make it more practical

@@xdsopl hell yeah

@@ArclampSDR Cool, adding comb type pilot tracking proved to be useful indeed. I've also rebased your silly branch, so have fun!

I don't know why your comment is not shown and I had to search in CZcams Studio for it .. anyway, thanks!