New and Improved Sound Card Packet Interface
now with CW and tested with PSK31, and APRS
Most of the digital communications used in the amateur bands use some form of tone translation. One tone will represent a high and another tone will represent a low, and by shifting between tones data can be transmitted and received. The data is then fed to a computer program that decodes the data in to understandable language or pictures. Early on the tone decoding was done by a device called a TNC (terminal node controller), which is synonymous with a computer modem used on a wire line or telephone network. In fact the early TNC were modified computer modems. Now that most computers come with very advanced soundcards it is possible to connect your radio directly to your PC without a TNC by using the computers sound card and additional software. The following circuit is a description of the circuit and software needed to make the connections between your computer and your radio. I built this circuit to do APRS (automatic positioning and reporting system) on 144.390 MHz, and most recently have used it for PSK31 on 20 and 40 meters. Please refer to http://www.kc2rlm.info/soundcardpacket for a very good and complete discussion on sound card packet radio.
Please refer to the diagrams for the following procedure.
Setup and testing
if you are using a AGWPE dependent software like UI-View
PSK 31 (using MixW software)
1. Download MixW software with the instructions from http://www.mixw.net/.
2. Install MixW software on your computer.
3. Connect the soundcard interface between your computer and your radio. Both LEDs should light when the computer is "on".
4. Turn on your computer and start the MixW software.
5. Click on the speaker icon (bottom right corner of screen) and set your sound card levels.
6. Set the "Line In" and "Master Volume" to mid-range.
7. From the "Master Volume" page select "Options/Prosperities/Record"
8. Set the "Line Out" to minimum level. You can further adjust your audio-out using your radio volume control.
9. Set your radio to display "ALC" (auto-limiting-control).
10. Adjust R5 when you transmit so that ALC is "0". (you will need to readjust when you change frequencies).
Don't forget to read the MixW instructions!!
Foil side view
(3 13/16" x 2")
Reverse foil side view
Packet Interface Parts List
|T1||Audio transformer (800 ohm - 8 ohm)||1||42TL08|
|T2||Isolation transformer (800 ohm 600 ohm)||1||42TL016|
|P1, P2, P3, P4||Stereo plug 3.5 mm||3||171-2035||30-488|
|P5||9 pin D connector||1||571-7479042||DS9F|
|hood for 9 pin D connector||1||156-2009||DE9|
|R1, R2, R3||resistor
1K ohm 1/4 W
|R4||resistor 100 ohm 1/4 W||1||271-100|
pin female mobile connector (microphone plug)**
|1||specific to your radio||T700|
pin male mobile connector (microphone plug) chassis mount**
|1||specific to your radio||P700|
|PCB||printed circuit board||1||make using foil pattern|
|2 conductor cable ft||9||SMC222|
|8 conductor cable ft||3||SMC822|
|Misc mounting hardware|
|PCB making supplies|
information on sound card packet hookup and use
Packet Engine (AGWPE.ZIP)
if your PC is <100 MHz
if your PC is >100 MHz
specific to your radio the plugs shown are for an ICOM 1020A
return to home page
Copyright ©,Jerry Baumeister