ELECRAFT K 2 Betriebsanleitung PDF herunterladen (Seite 19)

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Circuit Details

U1 amplifies the I.F. signal, which is then detected by D2 (1N34A). Q1 reduces the gain of U1 in proportion to overall

signal strength, keeping the signal at D2 relatively constant. Negative-going pulses that are above the threshold

established by D3 and R3 turn Q2 on, triggering the one-shot (Q3/Q4). Q6 can be used to switch in a larger-value

capacitor, increasing the blanking time. The pulse output of the one-shot (GATE) saturates Q5, attenuating the signal at

the output of the band-pass filter. The band-pass filter creates a small delay between input and output, so that the GATE

signal arrives just ahead of the noise pulses. The controller, U3, decodes auxBus commands from the main processor. It

then controls power to the blanker (via Q7), pulse width (via Q6), and blanking threshold (via R3).

= On bottom of PC board.

KNB2 Noise Blanker

Band-Pass Filter

To RF Board, J12

0V = NARROW

PULSE WIDTH

W. Burdick

Noise Gate

E. Swartz

Pulse Amp

0V = HIGH

6V = WIDE

6V Switch

THRESHOLD

Elecraft

One-shot

6V = LOW

6V = OFF

PN2222A

0V = ON

2N3906,

PN2222A

MC1350

1 of 1

AUXBUS

RF Amp

RF OUT

2N3906

2N7000

12C509A

40 µH

2N7000

78L06

Rev. Sht.

1N34A

78L06

100

Date

1.2 µH

.001

.0068

.001

22µF

3.9K

100K

3.9K

1.8K

3.9K

2.7K

1.2 µH

3.9K

GATE

C10

AGC

1800

0.1

OUT

GP5

GP4

VDD

GP3

GP2

GP1

GP0

VSS

RP1

RP2

RP1

C15

12V

.001

C13

.01

C14

6NB

RP2

C16

RP2

C12

ALC

C11

220

RP1

GND

OUT

220

.01

1500

L1 L2

1234

5867

12 345 6 7 8

MC1350, 12C509A

Controller

R10

300

120

820

.01

C17

(-6 dB)

D8-19-02

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 30 31

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