handiko / arduino-aprs

Create simple APRS modulator using Arduino UNO

Hi there 👋

Handiko Gesang Anugrah Sejati, S.T.

I work primarily as a RF Engineer/RF Specialist who designed board-level RF Circuits for HF to Low-UHF range (3 MHz - 470 MHz). Occasionally, I posts articles on my website.

• Personal website: https://handiko.github.io/
• How to contact me: [email protected]

Primary Interest 🔭

• Software Defined Radio (SDR), I am quite proficient in using GNU Radio tools and already made a few of Out-of-tree modules here and here.
• Antenna and RF Design, I am experienced in designing and simulating various antenna using free software, like 4NEC-2 and MMANA-GAL. A few of the design results 1, 2, 3, 4, 5
• RF Data Telemetry & Data Communication, I designed a hardware and wrote code and GNU Radio module to make an APRS Transmitter using an Arduino UNO and APRS receiver on GNU Radio using RTL-SDR 1, 2, 3
• Algorithmic Forex Trading, I recently start to trade forex and written a forex swing trading strategy in MQL5 and Pinescript programming language. Trading Strategy Collections

Side Projects ⚡

• I own my private Amateur Radio Station, My Callsign is YC1SDL. Currently i am still upgrading my antenna system for 40m band (7 MHz).

I'm Currently Learning 🌱

• RF Filter Design Techniques, Primarily interested in low-cost HF-VHF RF Filter (Bandpass, Lowpass, ect.)
• Antenna Array Design, To improve my amateur radio station capabilities.
• Another Noise Cancelling Techniques, To improve/upgrade my NCL-100+ Noise Canceller capabilities.
• Low Noise RF Amplification
• Algorithmic Forex Trading

arduino-aprs's Issues

1200/2400 Hz tones

I see that you use 1200 and 2400 Hz tones everywhere. Shouldn't APRS use 1200 and 2200, as originally?

can't decode

audio nya ada di speaker, tapi di bila TX, DireWolf tidak bisa decode. kenapa yer?

sharing of your project Arduino ARPS

Hi @handiko ,
great work!
I'm sharing your project on my own open source catalog repository :
https://github.com/aeonSolutions/AeonLabs-APRS-CWOP-Library/

AFSK tone reversal

If you listen to the audio output of pin 2 using the Hello World example, you will notice that the preamble has a high pitch on every other transmission. Printing the first bit of each message looks like this:

MYCALL-1>APRS,WIDE2-1:>Hello World !!
1
MYCALL-1>APRS,WIDE2-1:>Hello World !!
0
MYCALL-1>APRS,WIDE2-1:>Hello World !!
1
MYCALL-1>APRS,WIDE2-1:>Hello World !!
0
MYCALL-1>APRS,WIDE2-1:>Hello World !!
1

The AFSK tones must be reversed on each transmission. Is this the expected operation?

Also, the comment says that the crc is calculated with 0x1024 but the code uses 0x8408:

/*

• This function will calculate CRC-16 CCITT for the FCS (Frame Check Sequence)
• as required for the HDLC frame validity check.
• Using 0x1021 as polynomial generator. The CRC registers are initialized with
• 0xFFFF
  */
  void calc_crc(bool in_bit)
  {
  unsigned short xor_in;

xor_in = crc ^ in_bit; // bitwise XOR
crc >>= 1;

if(xor_in & 0x01)
crc ^= 0x8408;
.
.
.

bell 102 tone 1200/2200 why 2400?

Hi, in simple aprs with arduino why do you use 2400 hz tone ?
It's supposed to be 2200 hz no ?