OH2NLT Experimental Digital HF receiver
"From Antenna to Numbers"
25.08.2006 /uppdate 14.03.2007
Main objective of this project is to learn signal processing. I am a self educated DSP man, not a professional. I have made this Digital HF Receiver hardware platform to test various Digital Radio concepts. Main components are Texas Instruments AFEDRI8201 IF ADC chip and Microchip dsPIC30F6014A DSP. Test board also contains RF band pass filters for 3,5 and 7 MHz HAM band. AFEDRI8201 AUX DAC is used for audio output. User interface is built on LCD, quadrature encoder and few buttons & potentiometers. More details can be found from schematic diagrams.
AFEDRI8201 chip provides all blocks for high speed RF signal processing. From AFEDRI chip we get "low sample speed" I and Q signals for future processing. Microchip 30F6014 DSP/controller is easy environment to do this low speed processing and general system control functions.
This is exciting project !
Block diagram of the experimental Digital HF RX board (pdf version here)
More information will be added here while the project evolves.
Board layout BCB picture Top | Bottom
Schematic diagrams:Page1(RF & audio) | Page2(DSP) | page3(PSU) | Page4(RF attenuator)
RF attenuator responce
Test software for the Digital RX board. This code is more collection of test and experimentation routines than fully functional receiver with fancy user interface. Anyway receiver is fully operational with this. I am pleased to hear if other experimenters are developing code for AFEDRI8201 chip. Software is compiled with Microchip C30 compiler. Limited "student version" should also work. There are no time critical things in the main code requiring compiler optimization. Time critical things (filter calculations) are coded with assembler.
OH2NLT Digital RX test software (v14.10.2006)
First numbers converted from antenna and heard as sound 14.09.2006.This is the picture of test setup.
Picture of the OH2NLT Digital Receiver board
Board fully populated | Front side | Back side 16.09.2006
Bottom / Heat sink | Regulators
Picture of the AFEDRI8201 chip.
Some audio samples recorded 22.09.2006 evening. Recordings are done with wide test filters loaded in the AFEDRI8201 chip. Recording location is Espoo Finland and antenna is 80m dipole low in the bushes. MP3 samples are left channel only.
AFEDRI8201 filtersFIR1 FIR2 Fir 2 is the meaningful filter. After fir2 we have Hilbert filters with pass band from about 100Hz to 3kHz.
MP3 recording from OH ham rag chewing frequency 3699kHz LSB
MP3 recording from CW band 3505KHz with some QRM
MP3 recording from Deutche Welle news 6075kHz AM
Receiver is finally boxed. Hammond 1402 instrument case was just large enough for the RX board. Bellow few pictures.
Regulators are thermally connected to the bottom cover
Face plate with white LCD display / front view.
Back plate. Note external ICD2 programming connector. New software can be loaded without opening the box.
Top view. PCB was not originally designed for box installation but connectors etc fit rather well for this application.
Box closed / speaker grill
OH2GWE is also experimenting with Digital RX.This is his rig.