• on Audio/Video/Photography
  • Published in issue 5/2012 on page 58
About the article

AVR Software Defined Radio (3)

Part 3: AM and FM, plus an active ferrite antenna

AVR Software Defined Radio (3)
As this series shows, the popular AVR microcontroller can be used for digital signal processing tasks. In this instalment we will look at a few experiments involving amplitude and frequency modulation, including a small DCF time code test transmitter. We will also extend the hardware by adding an active ferrite antenna which will allow longwave and mediumwave signals to be received. Learn moreMissed the Elektor Academy/element 14 AVR Software Defined Radio webinar? Click here for the recorded session!
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Products
Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor Members can exclusively download these files for free as part of their Membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Extra info, Update

Unfortunately there's an error in the component list and the text in the textbox nearby as printed in the magazine. You only need one coil former, not three. The coil former has 5 pins. Wind 50, 150 and 200 turns of the copper wire separately on your coil former, connect the ends of the windings to the separate pins of the coil former, like this: pin - 50 turns - pin - 150 turns - pin - 200 turns - pin so that the three coils will be in series. This way you will get three coils of 50, 200 and 400 turns respectively.

Components
Download the BOM list
The BOM (Bill of Materials) is the technically exhaustive listing of parts and other hardware items used to produce the working and tested prototype of any Elektor Labs project. The BOM file contains deeper information than the Component List published for the same project in Elektor Magazine. If required the BOM gets updated directly by our lab engineers. As a reader, you can download the list here.
Want to learn more about our BOM list? Read the BOM list article for extra information.

Active ferrite antenna
Resistors
(all 5%, 0.25W)
R1,R2,R4,R10 = 470Ohm
R3 = 4.7kOhm
R5 = 10Ohm
R6 = 22Ohm
R7 = 47Ohm
R8 = 100Ohm
R9 = 220Ohm
Capacitors
C1 = 47µF 25V, 20%, radial, 2.5mm, IAC 95mA
C2,C3 = 100nF 63V, 5%, MKT, 5mm or 75mm
C4 = 2x265pF + 2x20pF dual gang quad section tuning capacitor
Inductors
L1 = 4.7mH, 81mA, 132Ohm, radial, 3mm
L2 = rerrite rod, L = 90mm, D = 10mm
1 coil former, 10mm, 5-pin (see also "Exta info, Updates" tab)
24.5m (82 ft.) enamelled copper wire, 0.22mm diameter (#31 AWG)
Semiconductors
T1 = BC560C
T2 = BF245B (JFET)
T3 = BC550C
Miscellaneous
K1,K2 = 2-pin pinheader, lead pitch 0.1 in. (2.54mm)
JP1 = 10-pin pinheader, lead pitch 0.1 in. (2.54mm)
TP1 = PCB solder pin, 1.3mm diam.
PCB # 100182-1
Alternatively: kit, comprising PCB and all parts: # 100182-71
Alternatively: Combined kit; 3 kits plus BOB FT232 USB/TTL-converter: # 100182-72

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