Article
Preselector for Elektor SDR
Here’s the automatic tuning upgrade!
The performance of a receiver depends to a large extent on its input filters. A selective input circuit improves antenna matching and immunity to interference from other strong signals. The preselector described here allows the use of up to four filters, tuned under software control using varicap diodes. A tuned loop antenna is also described that lets you use the Elektor SDR receiver without an outdoor antenna.
Materials
Gerber file
CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD 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 the Elektor PCB Service service from its business partner Eurocircuits or AISLER as the best services for its own prototypes and volume production.
The use of our Gerber files is provided under a modified Creative Commons license. Creative Commons offers authors, scientists, educators and other creatives the freedom to handle their copyright in a more free way without losing their ownership.
PCB
Extra info / Update
Features
- Four tuneable front-end circuits
- Controlled by free SDR tuning software
- I²C bus control
- Long-, medium- and short wave reception
- 500 pF varicap diodes
- Suitable for use with a wire antenna, a loop antenna or a ferrite rod
Component list
Resistors
R1,R2,R3 = 100kOhm
Capacitors
C1,C2,C3,C4,C5,C6,C7,C8,C9 = 100nF ceramic
Semiconductors
IC1 = 78L05
IC2 = LM358N
IC3 = PCF8591P
D1 = 1N4001
D2–D5 = 1SV149 (www.ak-modul-bus.de)
Miscellaneous
4 inductors on former type T1.4 (www.ak-modul-bus.de)
DC power adaptor type NEB 21 R (Lumberg)
PCB, ref. 090615-1
Alternatively, kit of parts # 090615-71, contains partly populated board, coil formers, ferrite rod with coils
R1,R2,R3 = 100kOhm
Capacitors
C1,C2,C3,C4,C5,C6,C7,C8,C9 = 100nF ceramic
Semiconductors
IC1 = 78L05
IC2 = LM358N
IC3 = PCF8591P
D1 = 1N4001
D2–D5 = 1SV149 (www.ak-modul-bus.de)
Miscellaneous
4 inductors on former type T1.4 (www.ak-modul-bus.de)
DC power adaptor type NEB 21 R (Lumberg)
PCB, ref. 090615-1
Alternatively, kit of parts # 090615-71, contains partly populated board, coil formers, ferrite rod with coils
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