QRP CW transmitter. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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QRP CW transmitter. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Civil radio communications

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G.Pechen described the scheme of QRP CW-transmitter developed by N7KSB based on "ARRL HANDBOOK CD" materials. Chip 74NS240 (analogue - 1554AP4) is a high-speed CMOS buffer driver.

QRP CW transmitter

On one of its elements, a master crystal oscillator is implemented, the other four are used as PA, the remaining three are not used. At Upit. = 7,8 V (stabilizer 142EN8A) Pout = 0,51 W at 14, 21 MHz and 0,47 W at 28 MHz. In this mode, the microcircuit requires a heat sink glued to its body. LPF data are presented in Table 1.

Range(m)	10	15	20
C8 (pF)	330	470	680
C9 (pF)	100	150	220
L1 (turns)	3	4	5,5
L2 (turns)	7	10	12

L1 and L2 - frameless, wire with a diameter of 1,6 mm on a mandrel 10 mm, winding length 16 mm (28 MHz) and 25 mm (21 and 14 MHz). Using this transmitter and antenna GP N7KSB has worked with all continents and more than 30 countries

Author: G.Pechen; Publication: N. Bolshakov, rf.atnn.ru

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