  APRS technology is still exists and still developing among amateur radio.
However, in Indonesia there are still not many people who use and utilize APRS.
The high price of APRS modem and difficulties of getting APRS modems is one of
the factors affecting the public interest in APRS. In Indonesia, no one has
developed APRS modem, so that our paper will be discuss about design and
develop of APRS modem using cheap and easy components FSK modem IC TCM3105 and
ATmega2560 as microcontroller. The implementation of APRS standard protocol on
modem that has been made use C programming language on Arduino IDE and the
schematic design and printed circuit board layout use Proteus 8. IC TCM3105
selection is based on the specification of eligible components of APRS device
able to set the baud rate of 1200 bps with FSK modulation technique. The
ATmega2560 microcontroller is chosen as the information signal encoding
processor and calculate the CRC-16-X25 FCS (Frame Check Sequence) for the
information packet according to the standard AX.25 UI Frame APRS protocol.
AX.25 UI Frame APRS protocol consists of flag, destination address, source
address, digipeater address, control field, protocol ID, information field and
FCS. The result of this paper is APRS modem device that has been made can send
the APRS information packet very well. This is proved by APRS packet that has
been sent can be received and repeated by ground station of Pusteksat LAPAN
also connected on APRS international network in aprs.fi. In addition, the
information that has been sent from APRS modem can be decoded correctly by APRS
software decoder such as Soundmodem, AFSK1200, dan AX.25-SCS.
