Packet Radio Getting Started




 

    Getting on Packet:            
  •  There are two main methods to get an AX.25 ( http://www.tapr.org/pub_ax25.html ) terminal node controller (TNC) capability for packet radio. They are the hardware TNC and the software TNC methods. We have tried both in the past. The hardware method was easier and more reliable. Both methods require hardware of some sort, but the software method needs less hardware. The software method with AGPWE (more on this below) may have improved since we tried it, so build the interface and give it a try. If you decide to use the hardware method later, the interface can be used on HF digital modes with FLDigi, Winlink2000, WinMor, HF-ALE or any of the HF "soundcard" modes as well as the related VHF/UHF modes. 
 



    Software TNC method:            
  • 1. Interface - A simple radio to computer interface schematic by W7JI is posted in the Technical section of this site. A parts list along with ordering instructions is shown. The interface has been built by many hams and it works. A cable with the appropriate connector for your radio can be soldered right to the interface, or a 9 pin D-Sub could be used as a universal connector for all your radios. The other side of the interface goes to the audio input and audio output of your computer.
  • 2. Software TNC - The key to sound card packet is a free software program called AGWPE. AGWPE was written by George Rossopoulos, SV2AGW, and is an acronym for " SV2AGW's Packet Engine". The best place to read about it is (http://www.soundcardpacket.org/). AGWPE setup and operation was found to be difficult when it was tried. Things change, so give it a try and if it works we would be pleased to hear about it in the comments below.
 



Hardware TNC method:            
  • 1. TNC - For the hardware method you need a TNC. A lot of people have used the TNC-X, a kiss TNC ( http://tnc-x.com/kiss.htm ) based on a pic chip. A kit version with RS-232 is $50 from http://tnc-x.com/. If you feel like spending $199.99, the Kantronics KPC3Plus is a very good TNC as well. 
  • 2. Serial RS-232 to USB adapter - You will also need a Serial RS-232 to USB adapter. A good one that a lot of hams use because it has some of the important handshaking pins is the IOGear GUC232A, $15.99, (http://www.amazon.com/IOGEAR-Serial-Converter-Cable-GUC232A/dp/B000067VB7). Micro Center has an Inland, SKU 381152, Prolific PL-2303, based adapter for $7.99, http://www.microcenter.com/product/381152/USB_20_to_Serial_Cable_Adapter . Your mileage may vary. [Note from Prolific on Windows 8 drivers : "Dear Customers, We are glad to announce the release of our Windows 8 WHQL driver for PL-2303 USB-to-Serial/UART Controller. The PL-2303 Windows 8 driver can also be downloaded automatically via Windows Update. Just plug-in the PL-2303 USB device and Windows Update will download and install the latest drivers (Internet connection is required)." However, they also mention that the PL-2303HXA/XA EOL (End-of-Life) chip versions are not supported by Prolific for Windows 8. Prolific recommends buying interfaces with the PL-2303HXD (HX Rev D) chip or newer generation chip versions. If someone can clarify Prolific drivers in Win 8, please leave a comment below.]
  • 3. TNC to Radio Cable - A radio to TNC cable needs to be made for this method. Ask your ham friends to build one for your TNC and radio.
  • 4. Radio Tweaks - You radio may need some signal path tweaks. For example, the Kenwood TM-V7A needs $0.50 in parts to make it work better on packet. See http://www.febo.com/packet/layer-one/kenwood-tmv7a.html . Also, don't overdrive the radio with audio input, from the TNC, like many hams do. If you listen to correctly transmitted packet tones received on a second radio, they will appear to sound wispy and almost weakly. The lower frequency audio tone should never be louder than the higher frequency tone. Packet tones decode better on the receive end if there is less clipping. More on this at http://www.febo.com/packet/layer-one/transmit.html
  • 5. Raspberry Pi TNC-X - A version of TNC-X, the TNC-Pi, has been released. See TNC-Pi announcement and ordering instructions at http://www.tnc-x.com/TNCPi.htm . The TNC-Pi stacks right into the GPIO multipin connector and can use the Inter-Integrated Circuit (I2C) bus. This provides for a single Raspberry Pi to support multiple TNC-Pi's at the same time, since each TNC-Pi can be given a unique I2C address. A corresponding version of the G8BPQ software is released for the Raspberry Pi Linux and Ubuntu. Operating th G8BPQ software on the Pi may be important for minimizing power consumption, while on emergency power, for long periods since the Raspberry Pi uses very little power. Raspberry Pi info is at http://en.wikipedia.org/wiki/Raspberry_Pi or http://elinux.org/RPi_Hub or http://learn.adafruit.com/category/learn-raspberry-pi . A Raspberry Pi can be purchased locally (and nationally in US) from MCM Electronics http://www.mcmelectronics.com/content/en-US/raspberry-pi




                   Common to both methods:            
                  Raspberry Pi with a double stack TNCX-Pi

                  Raspberry Pi with a double stack TNC-Pi. The DB-9 connectors go to radios. The serial data goes directly through the GPIO multi-pin connector as I2C bus data to a mating stackable multi-pin feedthrough connector on the TNC-Pi.
                  Another view of the Raspberry Pi with a single stack TNC-Pi on top.
                     
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