Hi, Described here is a circuit setup for interfacing PC soundcard with radio equipment for transferring digital as well as analog base band signal in audio frequency range. Requires modem software for modulation and demodulation of baseband signal.
 |
|
Figure 1 Schematic Diagram
|
It uses three isolation transformers, of which one dedicated to PTT engages PTT logic of rig by using the right channel 1 KHz signal generated by software during each data transmission as a routine once configured.
Isolation Transformer Core Details
Isolation transformer uses MnZn ferrite toroid used in switching power supply and RF suppression ferrite bed’s, also found applicable for frequencies up to 1MHz including audio range. One can recycle toroid from old CFL’s as well as Electronic florescent lamp chokes. Toroid tested and used in this circuit is from ferrite manufacturer “Mahindra Hinoday” form VU land with mix type MSB-5S and part number –T10.
 |
|
Figure 2 Frequency vs. Permeability of
toroid MSB-5S
|
Transformer winding Details
Primary and secondary are maintaining 1:1 ratio in all three transformers. Each transformer consists of 150 bifilar turns of (39-42) SWG wire serving primary and secondary. One can also try separate individual windings instead of bifilar.
 |
|
Figure 3 Toroid winding and Dimension
|
Software Configuration
Software configuration involves configuring windows audio setup as well as modem software. Here fldigi is the software modem used. Following settings gave me optimum result.
Windows Audio Settings
 |
|
Figure 4 Setting the Right and Left
Channel speaker gain
|
 |
|
Figure 5 Microphone gain setting
|
Modem Software Settings
 |
|
Figure 6 Check the parameter PTT tone
on Right channel
|
 |
| Figure 7 Also check the PTT on right audio channel under Hardware PTT |
PCB
Downloads
PCB & Circuit: Download Link
My prototype
 |
| PC-Rig interface (my prototype on dot board) |
Reference
http://www.qsl.net/g4hbt/tcvr.htm
http://wordpress.codewrite.co.uk/ham/2014/04/04/homebrew-data-interface/
http://www.w1hkj.com/Fldigi.html
http://www.w1hkj.com/downloads/fldigi/FLDigi_3.22_Users_Manual.pdf
No comments:
Post a Comment