 BLF278  300Watts FM-broadcast (87.5-108MHz) broadband RF-amplifier
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 Resistors
 (values are in Ohms, metalfilm or metaloxide, unless otherwise noted)

 R1 = 47 (SMD chip-resistor or similar)
 R2 = 47 (SMD chip-resistor or similar)
 R3 = 3k9 (SMD chip-resistor or similar)
 R4 = 3k9 (1/2 watts
 R5 = 1k5 (3 watts)
 R6 = 12 (3 watts)
 R7 = 12 (3 watts)
 R8 = 6.8 (3 watts)
 P1 = 2k5, 10 mm DIA., horizontal mount (Piher)
 
 Capacitors
 (all chip capacitors are brand ATC, type: 100B unless otherwise noted)

 C1 = 27pF
 C2 = 22pF trimmer capacitor, green (Philips)
 C3 = 65pF trimmer capacitor, yellow (Philips)
 C4 = 100nF 
 C5 = 100nF
 C6 = 3.3nF
 C7 = 100nF
 C8 = 3.3nF
 C9 = 1nF (porcelain)
 C10 = 1nF (porcelain)
 C11 = 22pF (porcelain)
 C12 = 47pF (porcelain)
 C13 = 47pF (porcelain)
 C14 = 22pF (porcelain)

 Semiconductors

 T1 = BLF278 (Philips)
 D1 = 5.1 volts, 1.3 watts zenerdiode

 Transformers, coils

 TR1 = 1:4 broadband balun transformer
       Ferrocube, type: 2865000202 (Philips) with 2 brass tubes.
       14 x 14 x 8 mm (corematerial must have an operating frequency less or equal to 
       200MHz)
       Primary 2.5 turns teflon wire (innerwire of 3.3 mm Teflon coax will do)
       Secondary two brass tubes soldered at one end together (bias side) and the other
       ends are soldered to their resp. gate's of the BLF278 (see drawing)
 L1 = 1/2 turn hairpin aircoil, 26 x 11 mm (height x width), 2 mm AgCu wire diameter
 L2 = 3 turns, 10 mm internal diameter, 2 mm AgCU wire, 2 mm wirespacing
 L3 = 3 turns, 10 mm internal diameter, 2 mm AgCU wire, 2 mm wirespacing
 L4 = 3 turns, 10 mm internal diameter, 2 mm AgCU wire, 2 mm wirespacing
 Z1 = 50-Ohms Teflon coax, 2.3 mm DIA., 22.5 cm in length 
 Z2 = 50-Ohms Teflon coax, 2.3 mm DIA., 22.5 cm in length
 Z3 = 50-Ohms Teflon coax, 3.3 mm DIA., 24 cm in length
 RFC1 = rf-choke, 2-hole ferroxcube core (i.e. balun-core) with 1/2 turn, 2 mm CuL blank 
        wire through it
 RFC2 = VK200-19/4B broadband choke

Notes

AgCu = silver plated copper wire
CuL = magnetwire, enameled copper wire, insulated (rigid) copper wire e.t.c.
(Note:	2 mm equals approx. to #12 A.W.G  
	1 mm equals approx. to #18 A.W.G
	1.2 mm equals approx. to #17 A.W.G
        0.8 mm equals approx. to #20 A.W.G
	0.3 mm equals approx. to #28 A.W.G.)

(I)   all diameters are measured from the inside of the coils, i.e. 'internal' diameter.
(II)  make sure to mount the rf-transistor on a appropriate heatsink and use some thermal
      heatsink compound between the flange of the transistor and heatsink!
      (Thermal resistance heatsink at least 6°C/W.)
(III) all parts are soldered directly on the toplayer of the pcb.
(IV)  bias is approx. 1.4 volts


(C)2006 Helix, Inc. The Netherlands.

