Elecraft KNB1 User Manual

E L E C R A F T K N B 1 N O I S E B L A N K E R

Assembly and Operating Instructions

Revision C, Jan. 18, 2001. Copyright © 2001, Elecraft; All Rights Reserved

Introduction

The KNB1 noise blanker can be used to suppress most pulse-type 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.

The noise blanker mode (
The two blanking thresholds provide more versatility in dealing with band and noise conditions.
Refer to Using the Noise Blanker for details.

The KNB1 plugs directly into the K1's RF board with no additional wiring. It is controlled by the
main processor on the control board via the K1's "AuxBus" network. Full circuit details can be
found at the end of this manual.

Specifications

Blanker Type I.F. pulse detector with wide-range AGC; two threshold levels

Current Drain Approx. 8 mA when turned on, < 1 mA off

Size 2.0 x 1.4 inches (51 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.

O F F , H I , L O ) is selected using the K1 transceiver’s N B menu entry.

Parts Inventory

Qty

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Q

Q3, Q

Q

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

consult the K1 Owner's manual, which has photographs of similar parts.

Ref. Description

C3, C12 Capacitor, disc, 10 pF, 5% 2 E530006
C1 Capacitor, disc, 180 pF, 5% ("181"
C9, C13 Capacitor, mono, .001 µF (“102”
C4-7 Capacitor, mono, .01 µF (“103”
C11 Capacitor, mono, 0.1 µF (“104”
C2 Capacitor, ceramic trimmer, 8-50 pF 1 E540000
C10 Capacitor, electrolytic, 2.2 µF 1 E530023
C8 Not used -- -­D1, D2 Diode, 1N4148 2 E560002
D2 Alt. Diode, Green LED (alternate for D2; see text
L1 Inductor, 25 µH, 22 T #26 on FT37-61 core (gra
L2 Inductor, 75 µH, 20 T #26 on FT37-43 core (gray w/orange dot
P1 Conn., 8-pin male, 0.1" spcg., gold, Samtec TSW-108-07-G-S 1 E620004

1-2, Q4, Q7 Transistor, NPN, 2N4124 4 E580006

8 Transistor, PNP, 2N3906 2 E580000

5-6 Transistor, MOSFET, 2N7000 2 E580002
R1 Resistor, 180 ohms, 1/4 W, 5% (brown-gray-brown
R2 Resistor, 3.9 k, 1/4 W, 5% (orange-white-red
RP1 Resistor network, 470 ohms, 5 resistors (isolated), 10 pins 1 E510015
RP2 Resistor network, 27 K, 4 resistors (isolated), 8 pins 1 E510019
U1 IC, Microcontroller, 12C509A 1 E610008
RF-J1 Conn., 8 pin female, 0.1" spcg., gold, Samtec SSW-108-01-G-S 1 E620005
HDWR Lock washer, #4, internal tooth (1 spare) 3 E700010

HDWR Machine screw, 4-40 x 3/16", pan-head phillips 1 E700015
HDWR Hex nut, 4-40 1 E700011
HDWR Standoff, 3/16" dia. x 7/16" long, hex M-F, 4-40 threaded 1 E700017
MISC Wire, #26 enamel 4 ft. E760002
MISC KNB1 PC board 1 E100106

Part No.

1 E530075
2 E530074
4 E530019
1 E530020

1 E570006
1 E680002
1 E680003

1 E500014
1 E500009

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Assembly

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A fine-point, temperature-controlled soldering iron is required to assemble this kit.

Excessive heat and/or large iron tips may damage pads and traces on the PC board.

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During assembly, we’ll refer to the top and bottom sides of the PC board. The top side
has most of the components. The bottom side has the model number and PC board revision.
(Note: The model number is KNB1. The revision C board is incorrectly labeled KBN1.)

Install resistors R1 (180 ohms, brown-gray-brown) and R2 (3.9k, orange-white-red) on the

bottom of the board. Solder them on the top side.

Install Diode D1 on the top side of the board. Orient the banded end of the diode as indicated

by its PC board outline. (D2 will be installed in a later step.)

Install resistor networks RP1 (470 ohms, 10 pins) and RP2 (27 k, 8 pins). (Be careful not to
confuse RP2 with connector P1, which also has 8 pins.) These networks are symmetrical and can
be installed in either of two orientations.

Locate the outline for transistor Q5. Adjacent to Q5 is a capacitor that may be labeled “C6”
(rev. C PC board) or “C9” (rev. D and later). Install C9 at this location (.001 µF, “102”).
Note: Do not pull on the leads of small capacitors, which can be fragile.

Install the following capacitors:

__ C3 (10 pf) __ C1 (180 pF, “181”) __ C11 (0.1 µF, “104”)
__ C4 (.01 µF, “103”) __ C5 (.01 µF, “103”)
__ C6 (.01 µF, “103”) __ C7 (.01 µF, “103”)

Note: The revision C PC board has a location for C8. This capacitor is not used.

If your PC board is revision D or later, install: __ C12 (10 pF) and __ C13 (.001 µF, “102”).

Install trimmer capacitor C2, with its flat side oriented as indicated by its PC board outline.

Install the 2N3906 transistors, Q3 and Q8. Orient the flat side of each transistor as shown by
its PC board outline. Keep lead length above the board no longer than about 1/8” (3 mm).

Install the 2N4124 transistors, Q1, Q2, Q4, and Q7.

Install the 2N7000 transistors, Q5 and Q6.

Install electrolytic capacitor C10 (2.2 µF), noting the orientation of the [+] lead. (Note: The
rev. C board has a disc capacitor outline at this location, with no [+] mark. Pre-form the leads of
C10 to fit the wider pad spacing. Orient the [-] lead toward Q8 and the [+] lead toward RP1.)

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