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1200baud Mini-TNC for APRS

Mini-TNC Rev0711 

FoxDigi: 1200 Baud Mini-TNC/Modem

VixenTrak: GPS-less Position Encoder for FoxView2

Hamcom Interface : Project & Kits

APRS Trackers & Viewers



 Mini-TNC: A 1200 Baud Radio Modem using PIC16F88


APRS/Packet  TNC.


 Mini-TNC V1.09
Latest Firmware Upgrade by Dennis/N5VRP

Firmware Document


Firmware V1.09

Evaluation & Test Report of Mini-TNC:
Doug / W5DUG

Bernard / KI6TSF

Uwe / SM6JWU


A Simple PIC88 based APRS TNC:

In this project, special attention is paid to get an economical APRS TNC with minimum current consumption and simple task:

1. A stand alone TNC to replace MX614 Modem chip

2. Send & Received APRS data to COM port.

3. Supports "Converse Mode" and Packet/APRS with Version 1.09 firmware by Dennis/N5VRP

Mini-TNC is a PIC88 based TNC which decode aprs packets & route to COM port. Mini-TNC has two D9 connectors for outside communications. J1, a D9F is provided for your transceiver. J1, another D9F is for connection to your PC using a simple serial cable to output your received data to your PC for further processing.

Mini_TNC require a supply of +12V (+7-12V) at DC connector J3 or same may be supplied at Transceiver connector J2 at PIN 7. An internal regulator (78L05) provides +5V for digital circuits. Current consumption is well below 20ma (Depending on LEDs) which is good enough for most remote solar powered locations. 

Mini-TNC uses a standard RS232 driver to interface with your PC. A null modem is required for configuration of PIC88's internal parameters, such as your callsign, Btext and if you want a digi enabled.

Project is designed on 10cm X 6cm Double Sided PTH board and results were very encouraging. A free metal case is avail;ble with kits or assembled.

PIC firmware for Mini-TNC is at 4800 baud, except for the newly upgraded Firmware V1.09 which is at 9600. Please refer N5VRP Document for more details on new firmware capabilitiies.

It should be noted that since no input audio preset is onboard, audio level supplied to this tnc may require careful adjustment of received audio from radio. 


Completed Mini_TNC

Click the image to enlarge

Mini-TNC back connectors:

Click the image to enlarge


Mini-TNC Document

1200 baud modem using MX614

V1.09 Formware Details by Dennis/N5VRP

1200 baud modem using MX614

Schematic & Parts List

1200 baud modem using MX614

Configuration Document

1200 baud modem using MX614

Using Hyper Terminal of Windows

1200 baud modem using MX614




1200 baud modem using MX614

Firmware (Basic)



N5VRP Firmware V1.09



With this modem, you can use many software available either as a freeware or shareware. Please go thru following links & find one suitable to your communication requirements.
Digital Communication Software Collection
Digital Communication Software links
Understanding Digital Communication

Please consider latest version of Mini-TNC





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