Elecraft AT1-41-dB User Manual

ELECRAFT AT1 Step Attenuator

Assembly and Operating Manual

E740101: Revision A, September 7, 2006

Copyright © 2006, Elecraft; All Rights Reserved

Introduction

The Elecraft AT1 is a versatile and accurate HF/VHF step attenuator that permits selecting any level of attenuation between 0
and 41 dB in 1 dB steps. The AT1 features an unusually high upper power limit of 2 watts, making it ideal for many
applications where attenuators with a lower power rating cannot be used such as at the output of a QRP transmitter for QRPp
experimentation.

The AT1 step attenuator is designed to be used as a stand-alone unit. Optionally, it may be built into existing equipment or an
enclosure of your choice. See Assembly Options on page 2 for more information.

The AT1 uses no surface-mount technology, so it’s an ideal project for first-time builders.

Specifications

Size: 5-3/8” x 2-11/16” (13.7 cm x 6.8 cm)
Range: 0 to 41 dB in 1 dB steps
Accuracy: Below 50 MHz: ± 0.25+0.01(A) dB
54 to 200 MHz: ± 0.50+0.01(A) dB

Where A is the attenuation selected in dB

Tools Required

You will need the following tools to build this kit:

• Fine-tip soldering iron. Recommend a temperature-controlled soldering station with 700 to 800°F tip (370-430°C).

• IC-grade solder (Kester #44 or equivalent). Small diameter solder (e.g. .031”) is easiest to work with on small

printed circuit boards. DO NOT use acid-core solder, water-soluble flux solder, additional flux or solvents.

• Diagonal cutters.

• Needle-nose pliers.

Parts List

We recommend that you do a complete inventory before beginning assembly. The inventory helps you correctly identify all
the parts to avoid mistakes during assembly.

Identifying Parts

The resistors in this kit all have value stamped on their bodies. For example, a 39-ohm resistor may be stamped “39Ω”.
Others, like the 910 ohm resistors may be marked with numbers similar to color codes. For example, a 910-oh m resistor may
be marked “911” indicating 91 x 10 or 910 ohms. In those cases the numbers you should find on the part are shown in
parenthesis after the value. There will be other numbers and letters stamped on them as well. You can ignore them. As long
as you find the numbers given, you have the right part.

Reference. Designator Description Qty

Misc. AT1 Step Attenuator printed circuit board 1 E100309
J1, J2 BNC Connector, PC Mount 2 E620020
R1, R3, R4, R6 910Ω (911) 1W Resistor 4 E500256
R2, R5 5.6Ω (5R6) 1W Resistor 2 E500257
R7, R9 300Ω (301) 1W Resistor 2 E500258

Part

Number

Elecraft • www.elecraft.com • 831-662-8345

Reference. Designator Description Qty

R8 18Ω (180) 1W Resistor 1 E500259
R10, R12 150Ω 2W Resistor 2 E500260
R11 39Ω (390) 2W Resistor 1 E500261
R13, R15 100Ω 2W Resistor 2 E500262
R14 68Ω 2W Resistor 1 E500078
R16, R18 62Ω 2W Resistor 2 E500167
R17 240Ω 2W Resistor 1 E500263
SW1, SW2, SW3, SW4, SW5, SW6 Slide Switch 6 E640032
Misc. Wooden Spacer (see Figure 2 on page 3). 1 E980131
Misc. Rubber Foot 4 E700024

Part

Number

Assembly Options

The AT1 is designed to operate as a stand-alone unit without an enclosure. Options are provided in case you want to build the
unit into an enclosure or existing equipment:

1. Your AT1 is provided with BNC connectors that mount parallel to the board. Normally these connectors will be

mounted on the top (silk screened) side of the board so that the board rests flat on the supplied rubber feet attached
to the bottom. However, if you are building the unit to place in an enclosure of your choice, you may elect to mount
the BNC connectors on the bottom of the board so the switches can be flush with the enclosure cover. Also, you may
purchase right-angle BNC connectors that may be mounted either on the top or the bottom of the board. Suitable
connectors are available from Digi-Key
(www.mouser.com

, part number 571-2272226).

®

(www.digikey.com, part number A32246-ND) or Mouser Electronics®

2. Four holes are provided in the board that you may use with your own #4 hardware and spacers as needed to mount

the unit instead of using the rubber feet.

Assembly Procedure

The finished Attenuator is shown in Figure 1. We recommend you follow the assembly procedure below, and refer to this
figure as needed.

Figure 1. Assembled AT1 Step Attenuator.

i

Use adequate ventilation when soldering; avoid inhaling smoke or fumes. Always wash your hands after

handling solder, as lead residue is highly toxic.

When applying solder, use the minimum amount required to surround the component lead and make good contact with its
printed-circuit pad. You don't need a "fillet" (build-up) of solder. This will avoid unwanted solder bridges and any need to
clean the PC boards.

The solder must flow onto both the component lead and its PC board pad. To ensure that both will be heated at the same time,
the tip of the iron should contact both the component lead and the PC board pad before solder is applied.

2