Elecraft KNB2 User Manual

E L E C R A F T K N B 2 N O I S E B L A N K E R

Assembly and Operating Instructions

Revision D, Aug. 20, 2002. Copyright © 2002, Elecraft; All Rights Reserved

Introduction

The KNB2 noise blanker can be used to suppress most wide-band noise, including that generated by
automobile ignition systems, power lines, and appliances. In many cases, signals that were completely
"buried" in noise will become easy to copy with the blanker turned on.

Various settings are provided to make the noise blanker more versatile. Two blanking pulse widths are
available, as well as two noise threshold settings. These selections are made using the K2's front panel
and L E V E L buttons, respectively. Refer to Using The Noise Blanker for details.

The KNB2 plugs directly into the K2's RF board with no additional wiring. It is controlled by the main
processor on the control board via the K2's "AuxBus" network. (Complete circuit details can be found on
the back cover.)

Specifications

Blanking Widths NB1, 10 µS; NB2, 70 µS

N B

Current Drain Approx. 13 mA when turned on, 2 mA off

Size 2.3 x 1.4 inches (58 x 36 mm)

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Caution: Some components in this kit can be damaged by static discharge. Before

handling any transistors or integrated circuits, always put on an anti-static wrist strap or touch any
grounded, unpainted metal surface.

Parts Inventory

p

Qty

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)

)

)

)

)

)

)

)

)

y)

Q1, Q2, Q4, Q

Q3, Q

Q

)

)

)

)

)

)

)

)

The table below lists all parts in the kit. If you have trouble identifying any of these items, consult the

K2 Owner's manual, which has photographs of similar parts.

Ref. Descri

C16 Capacitor, 39 pF, 5%, disc 1

C4 Capacitor, 100 pF, 5%, disc ("101"

C3 Capacitor, 820 pF, 5%, disc or monolithic ("821"

C9, C11, C13 Capacitor, .001 µF disc or monolithic ("102"

C6 Capacitor, 1500 pF, 5%, disc or monolithic ("152"

C7 Capacitor, 1800 pF, 5%, disc or monolithic ("182"

C12 Capacitor, .0068 µF disc or monolithic ("682"

C8, C14, C17 Capacitor, .01 µF disc or monolithic ("103"

C10 Capacitor, 0.1 µF disc or monolithic ("104"

C15 Capacitor, electrolytic, 22 µF1

D2, D3 Diode, 1N34A (alternates: 1N191, 1N5711

L1, L2 Toroidal inductor, 1.2 µH, 16 turns #26 on T37-2 core (red

L3 Toroidal inductor, 40 µH, 15 turns #26 on FT37-43 core (gra

P1 Conn., 8-pin male, 0.1" spcg., gold, Samtec TSW-108-07-G-S 1

7 Transistor, PNP, 2N3906 4

5 Transistor, NPN, 2N2222A 2

6 Transistor, MOSFET, 2N7000 1

R8 Resistor, 120 ohms, 1/4 W, 5% (brown-red-brown

R4, R5, R6 Resistor, 220 ohms, 1/4 W, 5% (red-red-brown

R9 Resistor, 300 ohms, 1/4 W, 5% (orange-black-brown

R3 Resistor, 1.8 K, 1/4 W, 5% (brown-gray-red

R7, RF-R88 Resistor, 2.7 K, 1/4 W, 5% (red-violet-red

R10 Resistor, 1 megohm, 1/4 W, 5% (brown-black-green

R1 Resistor, 100 K, 1/4 W, 5% (brown-black-yellow

RP1,RP2 Resistor network, 3.9 K, 4 resistors (isolated), 8 pins 2

U1 IC, RF amplifier, MC1350P 1

U2 IC, voltage regulator, 78L06 1

U3 IC, Microcontroller, 12C509A (alternate: 12C508A

tion

.

1

1

3

1

1

1

3

1

2

2

1

1

3

1

1

2

1

1

1

(parts list continues on next page)

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Ref. Description Qty.

J12 (RF board) Conn., 8 pin female, 0.1" spcg., gold, Samtec SSW-108-01-G-S 1

HDWR Split lock washer, #4 (Note: 2 spares provided) 6

HDWR Machine screw, 4-40 x 1/4", phillips 2

HDWR Standoff, 3/16" dia. x 3/8" long, round, 4-40 threaded 1

MISC Wire, #26 enamel 3 ft.

MISC KNB2 PC board, Elecraft P/N E100087 1

Assembly

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The noise blanker board will be mounted directly above the K2's I.F. amplifier transistor,
Q22. To avoid shorts between the bottom of the noise blanker and Q22 (or Q22's heat sink), you must
trim all noise blanker component leads to 1/16" (1.5 mm) or less. Flush-cutters are ideal for this. If
you don't have flush-cutters, trim leads close to the board before soldering.

including C15). Bend the leads of each capacitor slightly to hold it in place. Trim the leads before soldering
or flush-cut afterward, as described above.

banded end of each diode as indicated by its PC board outline.

Install all of the capacitors in the order shown in the parts list (C16, C4, C3, etc., up to but not

Install electrolytic capacitor C15 with its positive (+) lead inserted into the hole labeled "+".

Install Diodes D2 and D3. These are glass-bodied diodes and should be handled carefully. Orient the

Install all of the transistors (Q1-Q7). (Note: Be sure not to install a transistor at the location labeled
"U2," near the standoff hole. U2 is a voltage regulator IC.) Transistors should be mounted so that their
bodies are approximately 1/8" (3 mm) above the PC board. Re-check each part number against the list
before soldering.

Install resistors R8, R9, and R10, which are located on the top side of the board near U1 (MC1350).

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In the following step, you'll install several resistors on the bottom side of the PC board. Since
components on the top side of the board are very closely spaced, you should solder the bottom-mounted
resistors on the bottom side. This will prevent damage to top-mounted components. To avoid difficulty in
trimming resistors leads, pre-trim the leads to the correct length before mounting.

clearance is maintained for the I.F. amplifier (RF board, Q22), keep the resistors flush against the bottom of
the board. Pre-trim the leads and solder on the bottom side as explained above.

Install the remaining resistors, all of which are on the bottom side of the board. To ensure that

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