


Number of turns (N)







Measured inductance (L, µH)
















Hypothesis






Vdc (V)






Idc (A)






Pin (W)






Pout (W)






Zout (ohm)






X_{L } (ohm) (= 6 x
Zout)






L (µH) @ 136 kHz






The complete formula should consider the voltage drop on the mosfet:
Zout = (Vdc  V_{ DS(on)})^{2 }/ 2Pout (2)
If you are designing a push pull stage you can apply the following formula: (TNX G0MRF, David Bowman)
Zout (drain to drain) = 2 (Vdc  V_{ DS(on)})^{2 }/ Pout (2bis)
The ARRL handbook suggests that RF non resonant transformer must have an inductive reactance (X_{L}) at least 4 times the impedance. I decided to use X_{L= }6 times the impedance.
On the basis of the preceding experience I decided for the column 5 hypothesis, so for primary winding:
Z = 4.1 ohm and L = 28.8 µH
From table 1 the primary winding must have 10 turns (28,3 µH).
The secondary winding should match the antenna impedance, in my case about 50 ohms. Table 3 report the secondary winding turns, computed with the following formula:
(Npri/Nsec)^{2} = Zpri/Zsec (3)


Number of turns

15

20

25

30

35

Z secondary (ohm)

9,2

16,4

25,6

37

50



C1

10µF 35V

Electrolytic

C2

2.2µF 250V

Polyester

C3

2.2µF 250V

Polyester

C4

0.1µF

Ceramic

C5

2.2nF 1000V

Polyester

C6

10nF 1000V

Polyester

C7

0.47µF

Ceramic

C8

47µF 35V

Electrolytic

C9

4.7nF 1000V

Polyester

C10

3.3nF 1000V

Ceramic

C11

22nF 1000V

Polyester

C12

10nF 1000V

Polyester

C13

2.2nF 1000V

Polyester

C14

4.7µF 35V

Electrolytic

C15

0.47µF 250V

Polyester

C16

10µF 35V

Electrolytic

C17

47000µF 70V

Electrolytic

D1

1N4004


D2

MBR150

Schottky 150V

D3

25 A 200 V

Bridge

F1

6.3 A


J1


Key connector

J2


VFO connector

J3


ANTENNA connector

J4


RX antenna connector

K1

SPDT Relay, 12V


L1

54uH

Amidon T2002, 64 turn
1 mm diam.
enameled

L2

54uH

Amidon T2002, 64 turn
1 mm diam.
enameled

Q1

BD136

With heat sink

Q2

2SK1029

With heat sink and fan

R1

2.2k


R2

3.9k


R3

150 ohms 2W


R4

33k


R5

100k


R6

680 ohms


R7

10 ohms 2W


R8

4.7k


R9

10k


R10

100k


R11

10 ohms


T1


See text

T2

2 x 30V 200W

Power supply transformer

U1a

TC4426


U1b

TC4426

Not used, ground the
input

U2a

4013

Not used, ground the
inputs

U2b

4013


Z1

270Veff

MOV or Varistor, not
mounted



