VHF FM Antenna Booster
New horizons in 3-metre band DXing
Together with a good directional antenna this high performance two-stage antenna amplifier for the VHF FM broadcast band will enable you to capture far removed (DX) stations. Alternatively, it will drastically improve reception of FM signals you’ve come to accept as marginal and noisy in your area. FM broadcast transmitters are normally meant to have a useful range of 30-100 km. Fine, but if you are in a fringe area, all you may get is a very weak signal, possibly even blotted out by a powerful station around the corner.
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.
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Component list
R1 = 10kOhm
R2 = 150kOhm
R3 = 1MOhm
R4 = 220Ohm
R5 = 100kOhm
R6 = 3Ohm3
R7 = 1kOhm
R8 = 1kOhm2*
P1 = 47kOhm preset H
P2 = 10kOhm linear potentiometer
Capacitors:
C1, C6 = 22pF ceramic
C2, C5, C14 = 22pF trimmer
C3, C7, C17, C18 = 1nF ceramic
C4, C9, C13, C15 = 100nF ceramic
C8, C10 = 10nF ceramic
C11, C16 = 100µF 25V radial
C12 = 3pF9 ceramic
C19 = 12pF ceramic
Semiconductors:
D1,D3 = 1N4007
D2 = LED
T1,T2 = BF965 or BF966S
Inductors:
FB1,FB2,FB3 = 5 turns 0.15 mm (38SWG) enamelled copper wire on ferrite bead
L1 = 7 turns 0.9 mm dia. (20SWG) enamelled copper wire; internal dia. 5mm; length 10mm; tap at 5 turns from ground
L2,L3 = 7 turns 0.9 mm dia. (20SWG), internal dia. 5mm; closewound
L4 = 30 turns 0.15mm dia (38SWG) enamelled copper wire on a 1MOhm 0.5W resistor
Miscellaneous:
K1-K4 = F socket, PCB mount
S1 = on/off switch, 1 contact
PCB, ref. 040145-1
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