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K3WWP - Reviews of QRP Rigs

This review of the DSW-40 transceiver was contributed by William K. Mabry, N4QA.

Even though it has been around for about a year, now, I began hearing about the DSW (Digital Small Wonder) series of Direct Digital Synthesis QRP CW transceivers only a few months ago, a (-.. ... .--) here and there on 40M at times of day when I knew that I wasn't hearing one of our Russian friends bidding farewell to someone. No, the "DSW" I was hearing was issued immediately after the words "rig here is". So, in early April, I read a few reviews of the 40M model and exchanged SEVERAL emails with Dave Benson, NN1G, owner of Small Wonder Labs, in which I asked, and he fully answered MANY questions about the rig. Satisfied with all the information I had gathered, I placed my order, for a DSW-40 plus the matching enclosure, which Dave received on 10 April 2000.

While I still very much enjoy operating the TS-440S A/T, which I purchased new in 1986, and a host of QRP radios, I must say that my new DSW-40 kit rig has been taking up a LOT of my time for the past two weeks since finishing it.

The single printed circuit board, at approx 2.8 in. x 4 in., is of the finest quality double-sided plated-through stock which I have ever seen. Efficient use of supply and ground planes... silkscreened and solder-masked, of course. And the parts layout... with no wire jumpers or unused component locations... very clean. All components are of high quality, as well.

Assembly is straightforward with, perhaps, the most difficult task being the placement and soldering of two relatively large Surface Mount Device inductors... If I can do it, believe me, so can you. All of the really small SMD's are preinstalled and tested for you. There are, also, four small toroids to wind... again, no problem. The remaining components... resistors, capacitors, transistors, etc. are through-hole devices and will be very familiar to even the casual kit-builder. The few wiring harnesses (for controls, jacks etc) are a piece of cake. Dave's manual is superb. It is complete with parts list, schematic diagram and a wealth of information about kit-building, alignment, troubleshooting and operating.

It is a QRP rig, so it powers-up on 7040 kHz (or on 7110 kHz , if the RIT switch is "on" during power-up). Don't forget to turn off the RIT after power-up at 7110 unless you really want RIT at that point! Speaking of RIT, any time the RIT is switched "off", the RIT value is zeroed... that is, the previous RIT value is not "remembered" by the rig. With RIT off, the transceiver can be tuned in either 50 Hz or 200Hz steps. The tuning rate is toggled between those two values by pressing in on the main tuning knob for a half-second or so. With RIT "on", the transmitter frequency is locked in place, leaving only the receiver tunable...and the RIT has a single tuning rate of 50 Hz per step. The frequencies are referenced to a highly stable and accurate 32 mHz clock oscillator module, rendering rock-solid frequency stability anywhere within the 40M band. The brain of the unit, a PIC also performs the task of frequency readout... in audible Morse Code, of course. The frequency readout function is executed by a quick tapping in of the main tuning knob. There is a built-in Mode B iambic keyer which, I must say, helps one to send some really smooth code. Keyer function indexing is initiated by momentarily pressing a tiny pushbutton switch and then the desired function selected by pressing a keyer paddle at the appropriate time as fully and logically described in the manual. An RF gain control pot rounds out the rig's front panel controls. On the rear apron are jacks for dc power, keyer paddles, audio out, and antenna. An 8-15 V power supply (not included) is needed to power the rig.

According to my new Oak Hills Research WM-2, the rig puts out a solid two watts of rf when powered by a 13.8 vdc @ 500 ma supply, and according to CHU, Canada, as tuned in on the DSW-40 on 7335 kHz, the rig is within 50 Hz of being exactly on frequency! My first contact with the rig from here in Southwest Virginia, was on a very noisy band with a ham up in Toronto, Ontario, who was running 300 milliwatts!... if that tells you anything about receiver performance.

As of this writing, I have not received that beautiful blue-anodized enclosure but that's ok because I've been very busy tinkering with the rig and interfacing it with a PC parallel port for some homebrew computer control of the rig (but, that's another story). The DSW-40 is truly of elegant design and I intend to enjoy it for some time to come.

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