با سلام

مطلبی راجع به فرستنده ساده 5واتی در رنج 7 مگابود جالب بود تقدیم می کنم

BUILD A 5 WATT 40 METER TRANSMITTER

As ham operators, we like to broaden our horizons by trying something new. There is nothing more

satisfying about this hobby than building your own transmitter. The circuit in figure 1 is a crystal

controlled CW transmitter with at least 5 watts of power. (The prototype generated 7 ½ watts) This

circuit was built on a Radio Shack universal board(276-168B) and worked extremely well the first time on

the air.

This circuit is unique in that it uses a power mosfet as a final rather than a conventional bipolar transistor.

The advantages are as follows:

a.)

Very high gain with almost 90% efficiency. (Only a small heat sink is required.)

b.)

Resistant to high SWR. 30 second key down with no antenna resulted in no dama

ge.

c.)

Power mosfets do not exhibit thermal runaway as with bipolar devices.

The disadvantages are that a bias voltage is required because the Gate threshold voltage can be

anywhere between 2 and 4 volts for any power mosfet. This bias must be adjusted for the particular

transistor installed in the circuit. In addition, a Zener diode is required to insure that the Gate voltage

never exceeds 20 volts. This circuit proves that the advantages far outweigh these requirements.

The adjustment of the bias voltage is critical and is adjusted by first turning R10 so that zero volts

appears on the Gate of Q4. Install an ammeter to the 13.8 volt supply voltage and apply power. At this

point the circuit should only be drawing just under 1 milli-amp. Now turn R10 slowly until the ammeter

reads about 5 milli-amps. This adjustment should never exceed 10 milli-amps. Turning R10 up too high

can cause damage to the power mosfet. Once adjusted, R10’s setting remains the same unless Q4 is

replaced.

All transistors can be purchased at Radio Shack and should not be substituted. Crystal Y1 is a 7.040

MHz crystal and can be purchased from Dan’s Small Parts & Kits or from Doug Hendricks. Send $3 to

Doug Hendricks, 862 Frank Ave., Dos Palos, CA 93620. (Specify 7.040MHz or 7.122MHz.) A small

heat sink is required for Q3 and Q4. S1 switches between transmit and receive modes so that no

damaging RF gets to the receiver being used. The frequency is fixed but a trimmer capacitor can be

installed in parallel or series with Y1 to allow some adjustment of frequency. Toroids can be purchased

from Dan’s Small Parts & Kits or from Palomar Engineers.

DE N1HFX

Parts List

R1

5.6K Resistor (Green, Blue, Red) ¼ watt

R2

15K Resistor (Brown, Green, Orange) ¼ watt

R3

2.2K Resistor (Red, Red, Red) ¼ watt

R4,R8

1K Resistor (Brown, Black, Red) ¼ watt

R5

4.7K Resistor (Yellow, Violet, Red) ¼ watt

R6

22 ohm Resistor (Red, Red, Black) ¼ watt

R7,R9

10K Resistor (Brown, Black, Orange) ¼ watt

R10

10K Trimmer pot, ¼ watt or larger

C1

.

01uf Ceramic disk capacitor

C2,C4,C6,C9

.1uf Ceramic disk capacitor

C3

.0028uf Ceramic disk capacitor (Use two .001uf capacitors and one 820pf

capacitor in parallel.)

C5

68pf Ceramic disk capacitor

C7,C10

.001uf Ceramic disk capacitor

C8

100uf electrolytic capacitor. (observe polarity)

C11,C13

390pf Silver Mica capacitor

C12

820pf Silver Mica capacitor

D1

15 volt Zener diode. 1N4744 or similar.

Y1

7.040 MHz or 7.122 Mhz crystal

T1

T50-2 toroid. 34 turns #26 wire for primary. 6 turns #22 wire for

secondary.

T2

FT37-43 toroid. 14 turns #26 wire for primary. 4 turns #22 wire for secondary.

L1

T68-2 toroid. 10 turns #22 wire.

L2,L3

T37-2 toroid. 16 turns #26 wire.

Q1

2N3906 transistor

Q2

2N3904 transistor

Q3

2N3053 transistor. Must use TO-39 or similar type heat sink.

Q4

IRF510 Power Mosfet transistor. Must use TO-220 heat sink(276-1363).

S1

Any suitable SPDT switch