Messages

1

The RF Workbench / Re: Arduschreiber HF-Beacon mkII

« on: July 19, 2020, 0636 UTC »

I accidentally overheated the circuit when it got stuck in transmission for a longer period of time(a wire short probably) whilst enclosed in a small airtight box, i think a couple of the components overheated. Since i didnt get the stability i wanted to be able to run slow hell i have started looking around after a better design of the PA-stage.

2

The RF Workbench / Re: Arduschreiber HF-Beacon mkII

« on: July 18, 2020, 0559 UTC »

I havent seen my tx on any of the web-SDR, so i tried to switch over to slow-hell but discovered that the PA has a bit of an issue with frequency drift when transmitting longer than the short pulse of field-hell. The signal starts our at one frequency, but then drifts about 250Hz higher during that "dot".

This is a problem with fldigi, since the filter is very narrow. When using the shorter field-hell "dots" this isnt seen, but it wouldnt bee an issue either since the fldigi filter is a lot wider.

The TX didnt have any other issues, so i will take if off the air and start building its enclosure and work a bit more on the code.

3

The RF Workbench / Re: Arduschreiber HF-Beacon mkII

« on: July 17, 2020, 1516 UTC »

Testing "CQ TEST" at 7001,6kHz, fieldhell, at 5W once every second minute from southern part of scandinavia. I will have a look at the web-sdr to get a picture of the range. The antenna is a longwire with a reasonable ground plane.

4

The RF Workbench / Re: Arduschreiber HF-Beacon mkII

« on: July 17, 2020, 1428 UTC »

This circuit gives a bit more than i expected, driven with 13v i get 5W out, with 55% efficiency! It also works surprisingly low in voltage. In standby mode the TX only uses 4mA. The frequency can be adjusted with about 2kHz, using the 22pf variable capacitor on the oscillator.

5

The RF Workbench / Arduschreiber HF-Beacon mkII

« on: July 15, 2020, 1619 UTC »

After having test run the mkI version in my garden with good results I have done a new construction of the transmitter, the basic design is the same but the source of the schematics is different(came with Chinese QRP TX from Ebay), some of the values are a bit different, and the source of the 74HC240 is other. I 3d printed a holder for the Arduino Nano, witch turned out nicely.

Now im just waiting for a few more components for the lowpass filter, according to the designer, the PA-stage will put out about 10W at 13.8v. Im expecting more lika 2-3W.

6

The RF Workbench / Re: HF beacon using Hellschreiber and Arduino, Ardushcreiber

« on: July 01, 2020, 0711 UTC »

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.

7

The RF Workbench / Re: HF beacon using Hellschreiber and Arduino, Ardushcreiber

« on: June 27, 2020, 1409 UTC »

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).

8

The RF Workbench / Re: HF beacon using Hellschreiber and Arduino, Ardushcreiber

« on: June 27, 2020, 1047 UTC »

Arduschreiber v1.2 is out!  The code is now updated with the complete GL character set.

https://easyupload.io/c5u15t

9

HF Mystery Signals / Rtty looking signal 4280kHz at UTC: 1420 Europe

« on: June 25, 2020, 1426 UTC »

Does anyone know what this signal is? Found it at 4280kHz, sounds a bit like RTTY, but i cant decode it like one of the ordinary RTTY modes. It transmitts for 3-4s, then pauses with only a carrier wave for 3-4s and then starts over.

10

The RF Workbench / Re: HF beacon using Hellschreiber and Arduino, Ardushcreiber

« on: June 24, 2020, 1938 UTC »

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!

11

The RF Workbench / Re: HF beacon using Hellschreiber and Arduino Nano

« on: June 23, 2020, 1635 UTC »

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

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 

12

The RF Workbench / Re: HF beacon using Hellschreiber and Arduino Nano

« on: June 22, 2020, 1742 UTC »

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..

13

The RF Workbench / Re: HF beacon using Hellschreiber and Arduino Nano

« on: June 22, 2020, 1734 UTC »

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

14

The RF Workbench / HF beacon using Hellschreiber and Arduino, Ardushcreiber

« on: June 21, 2020, 1233 UTC »

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.





Download link to arduinocode(Arduschreiber): https://gofile.io/d/FHAUjF

Edit: Moved code to txt-file in link to make thread more readable

15

The RF Workbench / Re: HF Beacon, design questions

« on: June 21, 2020, 0826 UTC »

Somehow the oscillator will not work with certain frequencies, it just doesnt oscillate(tested with the oscillator only). I will have to spend a little more time on the circuit this summer, and order a few more crystals.