Article

20-Meters Band Receiver

an unusual double-conversion superhet

This SSB/CW receiver for the popular 20-m amateur radio band boasts a number of interesting features. Designed as a double-conversion superheterodyne with a direct-conversion demodulator, it offers adjustable IF bandwidth and is remarkably simple to adjust. What’s more, the single-board concept makes the receiver easy to build, even by relative newcomers to the radio hobby.A number of design aspects should be considered when blueprinting a 20-m band SSB receiver that is going to be reproducible. Besides the obvious aspect “receiver performance” there are other essential considerations like availability and price of the components used. Such considerations immediately rule out the use of, for example, a professional SSB filter which would cost you £30 or more.

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Materials

010097-PCB.pdf

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.

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PCB

Download Gerber file: 010097-1.zip

Component list

Resistors:
R1,R21 = 1MOhm
R2 = 150kOhm
R3,R15 = 100Ohm
R4,R5 = 1kOhm 2
R6,R11 = 18kOhm
R7 = 1Ohm k8
R8 = 560kOhm
R9,R10,R13,R19 = 4kOhm 7
R12 = 3kOhm 9
R14 = 68kOhm
R16 = 1kOhm
R17 = 330kOhm
R18 = 330Ohm
R20 = 47kOhm
R22 = 2kOhm 2
P1 = 50kOhm 10-turn cermet
P2,P3 = 5kOhm linear
P4 = 50kOhm
P5 = 5kOhm preset
P6 = 25kOhm preset
Capacitors:
C1,C46 = 40pF trimmer
C2,C3,C10,C13,C17,C22,C27,C33,C34,C37,C38,C40,C42 = 100nF
C4,C26,C31,C39 = 10nF
C5,C7,C15 = 68pF
C6 = 2pF2
C8,C9,C12,C14 = 1nF
C11 = 4pF7
C16 = 22pF
C18 = 33pF
C19 = 3pF3 *
C20 = 27pF
C21 = 56pF
C23 = 10µF 16V radial
C24,C32,C36 = 22nF
C25 = 470µF 16V radial
C28 = 330pF
C29 = 470pF
C30 = 12pF
C35 = 22µF 16V radial
C41 = 1µF 16V radial
C43 = 220nF
C44 = 220µF 16V radial
C45 = 10µF 16 V radial
Semiconductors:
D1,D3 = KV1235 (1 V/500 pF, 8 V/25 pF)
D2 = not used (do not mount)
D4 = zener diode 5V1, 400mW
D5,D6 = BAT85
D7 = 1N4001
IC1,IC2,IC5 = NE612 or SA612AN
IC3 = LP2950CZ-5.0 (possibly 78L05)
IC4 = LP2951CN
IC6 = MAX7400
IC7 = LM386N3
T1,T3 = BF981
T2 = J310
T4 = BS170
Miscellaneous:
FL1 = GS21G15A or GS21G15B
FL4 = CSB455E
Fl2,Fl3 = SFR455J
L1,L3 = 5µH6 miniature choke
L2 = 1µH2 miniature choke
LS1 = 8 Ohm /1W loudspeaker
M1 = 0.1 – 0.25 mA moving-coil meter
Tr1,Tr2 = 94AES30466N or 94ANS30466N
X1 = 20.945MHz quartz crystal (parallel resonance, 3rd overtone, 2x20pF)
K1 = mains adaptor socket, PCB mount
PCB, order code 010097-1