Table of Contents
WAOARC 2025 WSPR Kit Build - Construction Guide
This guide will walk you through putting the WSPR Hat Kit together.
Please ask in the #waoarc-kit channel on Discord if you have any issues or questions.
Prerequsites
In your kit, you should have received the items in the table below. Please check you have everything before you begin:
| 1x 20k variable resistor | 1x 47uf 16v Electrolytic Capacitor | 2x 4-pin sockets |
| 1x 47Ω resistor (Yellow Purple Black Gold) | 3x 100nf Capacitor marked BC 104K | 1x 40-pin socket |
| 1x 20KΩ resistor (Red Black Orange Gold) | 1x BS170 transistor | 15cm fine enamelled copper wire |
| 1x 1Ω resistor (Brown Black Gold Gold) | 1x LED (orange diffused) | 1x SMA Edge-mounted socket |
| 1x 15KΩ resistor (Brown Green Orange Gold) | 1x 1N4148 Small Signal Diode, 100 V, 150 mA, 1 V | |
| 1x 270Ω resistor (Red Purple Brown Gold) | 1x Push button momentary switch | |
| 1x 2KΩ resistor (Red Black Red Gold) | 1x FT37-43 Ferrite |
The kit also requires a QRPLabs Low Pass Filter. If one was requested with your kit, it will be included in it's own ziplock bag.
Resistors
Install all the resistors and trimmer variable resistor. The board is marked to assist you.
Tip - Try to have the coloured bands in the same orientation. It looks nice.
| Reference | Component |
|---|---|
| RV1 | 20KΩ Trimmer variable resistor |
| R2 | 47Ω (Yellow Purple Black Gold) |
| R3 | 20KΩ (Red Black Orange Gold) |
| R4 | 1Ω (Brown Black Gold Gold) |
| R5 | 15KΩ (Brown Green Orange Gold) |
| R6 | 270Ω (Red Purple Brown Gold) |
| R7 | 2KΩ (Red Black Red Gold) |
Capacitors
Install the capacitors.
NOTE: C1 is an electrolytic capacitor so the orientation is critical or the magic smoke may escape. Long leg is positive, and short Leg is negative. Match the white band on the capacitor to the white area on the board
Tip - Try to orient the other capacitors so the writing faces the edge of the board and can be easily read.
| Reference | Component |
|---|---|
| C1 | 47uf 16v Electrolytic Capacitor |
| C2, C3, C4 | 100nf Capacitor marked BC 104K |
Transistor
Install the transistor.
Make certain the direction installed matches the silkscreen on the board
(Flat surface towards edge).
| Reference | Component |
|---|---|
| Q1 | BS170 Transistor |
Diodes
Install the diodes in poistions D1 & D2.
Note the orientation of the diodes. The LED short leg must be closest to the edge of the board. The signal diode has a black stripe on one end which may be hard to see. It should be positioned closest to the edge of the board, matching the outline on the board.
| Reference | Component |
|---|---|
| D1 | LED (orange diffused) |
| D2 | 1N4148 Small Signal Diode, 100 V, 150 mA, 1 V |
Switch
Install the push button switch. The switch and it's mounting holes are slightly rectangular. It will work in either of the two possible orientations.
| Reference | Component |
|---|---|
| SW1 | Push button momentary switch |
Inductor
Wind the ferrite core with 4 turns of wire as shown. Each time the wire passes through the centre counts as one turn.
Note: Crop the leads longer than necessary, and scrape, sand, or heat the coating to remove it before fitting and soldering. Heating can be done with a lighter, or a very hot soldering iron.
| Reference | Component |
|---|---|
| L1 | FT37-43 Ferrite with 4 turns of wire |
 |  |
Connectors
Connector J2 (the 40-pin) is positioned on the underside of the board.
Connectors J5 & J6 are fitted to the component side of the board.
Connector J4 (the SMA socket) is positioned on the edge of the board, with the centre pin connection on the top, component side of the board. All 4 ground pins should be soldered to the board, not just the pair adjacent to the centre pin.
| Reference | Component |
|---|---|
| J2 | 40-pin socket |
| J4 | SMA edge-mounted socket |
| J5, J6 | 4-pin socket |
 |  |
Filter Installation
When connecting your filter, (build instructions at https://qrp-labs.com/images/lpfkit/assembly_A4.pdf) you should ensure that is inserted in the correct orientation. The filter has 'IN' and 'OUT' text on the ends, and you need the 'OUT' nearest the SMA connector.
