HFU HF Underground
Technical Topics => The RF Workbench => Topic started by: greator on June 21, 2020, 1233 UTC
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I thought i would share a small side-project, sending Hellschreiber from a small HF-beacon using a arduino. I took some effort to write the code in such a manner that it would fit in memory of a Nano, but it worked in the end! The code is simple tu use, just enter a string and it will send it.
Hell has a few good low-power alternatives, as slow hell. It should just be a question of setting the "speed" right(the number of micro seconds each dot take). But i have only gotten it to work with the normal field hell so fat.
(https://i.postimg.cc/Y06DLNsg/bild.png)
(https://i.postimg.cc/t4pL0zq8/bild.png)
Download link to arduinocode(Arduschreiber): https://gofile.io/d/FHAUjF (https://gofile.io/d/FHAUjF)
Edit: Moved code to txt-file in link to make thread more readable
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Very cool! Let us know when (and what frequency) you get it on the air!
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I did some test with slow hell, at 1/8 of the speed of feld hell, it worked nicely. I had to re-make some of the code but it was done quickly, the longest microsecond delay is something like 16000us and you need about 32ms in on/off time in slow mode. There is now a comment describing what time to youse, in the code.
It would be interesting to see if there is any program that can recieve even slowe Hell than the oridnary 1/8-speed of Feld.
https://gofile.io/d/FHAUjF (https://gofile.io/d/FHAUjF)
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The code function in the forum doesnt seem to work, it looked nice in preview but when i posted it just unfolded. Perhaps the code is simply too long for a post..
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I thought i would share a small side-project, sending Hellschreiber from a small HF-beacon using a arduino.
This is very, very cool. Any chance that you have, or could supply, a step-by-step project page (via the Internet) for building one of these?
I have toyed around with Arduino, but not enough to just build something like this without a lot of assistance, typically in the form of websites that show step by step how to wire up, what kind of antenna to use, etc. And posting the code somewhere as a .txt file or on the web would really help.
Thank you. And thanks for sharing this.
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Thanx for the comments! I will try to make a better description of the transmitter/arduino package and how to build it. The code is available in .txt format on the link below :)
I have named the program Arduschreiber, and this is version 1.1 updates were done on a few points:
- What pin to key transmitter is now set globaly
- Speed setting available in code to switch between feld-hell and slow-hell
https://gofile.io/d/FHAUjF (https://gofile.io/d/FHAUjF)
Next step will probably bee to add the special characters(-,/+- etc) to the code, now its only alphabet, space and numbers. The program takes up 22% of flash and 36% of SRAM on the arudino nano(Atmega 328p), to more characters is not a problem. The key to solve this is to store letter efficiently, before i solved this i could only fit about 10 letters. Now each 1/0 is a bit, before it was a whole byte :-*
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Thanx for the comments! I will try to make a better description of the transmitter/arduino package and how to build it. The code is available in .txt format on the link below :)
Excellent, thanks. Questions: Is the photo that you posted above just the transmitter part of the Ardushcreiber? I can't tell by looking, but I don't see the Arduino Nano there.
And thanks for the code.
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The arduino Nano is glued to the under side of the circuitboard :) I used hotglue to attach it, and it worked really well. I will post a couple of pictures soon!
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Arduschreiber v1.2 is out! ;D The code is now updated with the complete GL character set.
https://easyupload.io/c5u15t (https://easyupload.io/c5u15t)
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I am testing out a beacon using Arduschreiber, using a 20W solarpanel. I got it running in the QRP spectrum of 40m, so i am going with 175mW of output to not cause any interference. There is no battery backup, so it will probably be running between 06.00 to 21.00 each day.
The beacon sends a short bit of text with some information, and the temperature, i am messuring it with a 1N4148, the forward voltage is about 0,6 volts depentent on temperature, about -2mV per degree celcius. With the internal adc refence of an arduino on 1,1v it works pretty well.
The transmitter is built into a watertight box, and all connections are sealed with melting glue.
Frequency: 7028.33kHz
Interval: 3 minutes
Mode: Slow-hell
Power: 175mW
Antenna: Simple longwire antenna, 5m with a couple of meters of ground wire.
Here is a short descreption of how i wired the Arduino to the keyer, and the temperature temperature sensor(diode).
(https://i.postimg.cc/bNWvptTC/bild.png)
(https://i.postimg.cc/cCDGCRZK/bild.png)
(https://i.postimg.cc/15gjDhr7/bild.png)
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The beacon has worked nicely since i put it up for testing, it even seams to be watertight enough to withstand the climate. The only thing i will need to fix is that when the voltage drops(sunset) the beacon starts to transmit, sends a short beep, and then the voltage drops and the Arduino restarts on low voltage, and sends another beep etc... I will add a voltage check that needs to pass before transmission starts.
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Thanks for the code. I'll see if I can port it to an ATtiny.
I have those running now with QRSS code. 2mA ......