Small Wonder Labs DSW-40

The photograph above shows the DSW-40. This is a very nice little CW transceiver from Small Wonder Labs company, operated by Dave Benson, K1SWL. The rig in the photograph is one of the last 100 of the original DSW kits produced and is shown dressed up in the SWL custom anodized case. This model of the DSW was discontinued in the fall of 2000 due to difficulty in obtaining the DDS integrated circuit chips.

In June 2003, SWL introduced the DSW-II series of CW transceivers. The DSW-II is a totally redesigned rig and was packaged in a different case.  Small Wonder Labs is no longer in business, however the DSW series of transceivers are still popular items.

The DSW-40 in the picture above was very easy to build. SWL's instructions were excellent and written with the beginner in mind. There were only four toroids to wind, and three of them have only a single winding. There were two surface mount inductors to be soldered to the board, but no worry as they were the "large" SMT parts and were soldered first before the board got crowded.

The DSW's innards are exposed in the photograph on the left. The antenna coax cable is the only wiring that is soldered to the circuit board. All other wiring uses multi-pin cables for the off-board connectors and controls. The circuit board snaps into four standoff posts which makes board access for service or modifications very easy.

The DSW uses a three pole crystal filter and a pair of NE602 mixer chips in the receiver chain. The IF is at 4.032 MHz for the 40 meter receiver. The transmitter mixer and tuned bandpass filter is conspicuously missing in the DSW's design. This is because the clean 7 MHz transmit signal generated by the DDS frequency generator chip does not contain spurious mixing products. The transmitter final amplifier stage uses a RCA 4013 transistor to produce 2 watts of output power.

Note that for this final production run of 100 DSW's, the main tuning step encoder has been changed from previous production units due to a parts availability problem. The earlier units used encoders with a push function that was used to control the tuning step size. In this final production run, the tuning step size is controlled by the RIT switch, which was changed to a center off, spring return (on the down side only).

In over 40 years of building ham equipment, this is the first rig that I have built that could have been put on the air without any testing or alignment. On the first power up, it heard 40 meter CW signals on 7040 kHz without touching any tuning or alignment controls. The transmitter was putting out 2 watts! Actually, there are only two alignment steps: one to set the transmitter offset and a second step to peak the receiver input coil.

The DSW is a 2 watt CW monoband transceiver. The thing that makes it unique is that it uses an advanced digital VFO, making it immune to drift. It tunes in steps of 200 Hz per step initially, or by pressing the RIT switch down, it shifts to 50 Hz per step. Also, you get unlimited RIT range, perfect for working split frequency DX.

On power up, the DSW-40's digital VFO sets the frequency to 7040 kHz, or if the RIT switch is on, it initializes at 7110 kHz in the former Novice/Tech sub-band. Frequency coverage is the entire band.

The CW keyer is built-in, with speeds of 5 to 50 wpm. Also built-in is an AFA (Audio Frequency Annunicator) that announces your operating frequency in Morse code.

This little rig drew first blood in the February 5, 2001 Cub Fox Hunt when it easily worked NIT for another fox pelt for the shack wall.

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Updated June 15, 2016