40-Meter QRP Transceiver
Small Wonder Labs
This is the latest addition to my collection of QRP rigs -- the Small Wonder
+ , SW+ 40-meter QRP transceiver from Small Wonder Labs (SWL ). SWL also
makes the RockMite QRP rig and the FreqMite frequency counter that I describe
elsewhere on this site.
Small Wonder Labs
The SW+ series rigs are available for 80, 40, 20, and 30 meters. Dave
Benson at SWL sells this rig as a kit; he also sells an enclosure kit that
includes a silk-screened, pre-drilled enclosure as well as all controls, jacks,
and connectors needed to mount the SW+ in the enclosure. (UPDATE:
As of late 2010, Dave no longer sells the enclosure kit. The aluminum box
that he used is a TenTec model
TG-24 enclosure. The
TenTec TBP-19 is also suitable.)
Here's a link to the SWL website:
On the left side of the SWL front page you will see several links --
click on the link to SW+ Series to see the SW+ and the enclosure kit.
My Experience with the SW+ for 40 Meters
I ordered my SW+40 on 19 January 2010 and received it two weeks later, on 30
January. The kit arrived in the mail at the beginning of a HUGE snowstorm.
When I went to the mailbox, the wind was blowing from the north -- across the
Potomac River -- at 20 MPH with gusts to 30 MPH and snow was falling at the rate
of an inch an hour. I brought the kit into the house, ate lunch, then
started assembling the rig.
Assembly was straightforward. Dave includes with the kit a CD that has
the latest version of the assembly instructions. Also, you can print the
instructions from his website. I printed extra copies of the parts list
and the parts placement diagram to use while building the rig. As I placed
parts on the PC board, I checked them off on the parts list and the parts
Total construction time from opening the box and dumping out the parts to
putting the rig on the air was six hours, including an occasional break.
I had no problems in building or tuning the rig -- it worked perfectly the
instant power was applied.
Here are some photos
First is a picture that I copied from the Small Wonder Labs website showing a
close-up view of the PC board.
Note the four crystals lined up from right to left down the
center of the board. Three of these form a crystal filter for the receiver
that makes it quite sharp and knocks out most interference when the band is
Here's a picture of my SW+40 laid out after I tested and tuned
Here is the SW+40 with all connections laid out on my operating
table. The red and black lead from the left is power. The
red-yellow-orange leads that go to the small knob on the left are the volume
control. The big knob in the front center of the photo is the tuning
control. The small PC board is a
FreqMite frequency counter
from SWL -- this is a separate item, not part of the SW+40; I wired it into the
SW+40 to give me an audible readout of the operating frequency. The
green-yellow-orange lead on the right goes to two jacks -- key and headphone.
To the upper right of the SW+40 is my KK-1
straight Key from American Morse Equipment. To the right of the
key is a big silver connector -- this is the antenna connector. The tiny
silver object to the right of the FreqMite is the switch that activates the
FreqMite. I laid out the rig in this configuration to test it and tune it.
Tuning took only a couple of minutes. As soon as it was
tuned, I made two contacts with the rig, one in central Tennessee and one in New
Here's an out-of-focus close-up photo of my SW+40.
Specs for my SW+40
Frequency coverage: 7026 - 7068 KHz.
Power output: 1.25 watts. The rig is capable
of putting out 2.5 watts and output power is adjustable from under 1 watt to 2.5
watts. I set mine at 1.25 watts.
Tuning: Tuning is accomplished by varying the
voltage across a varactor diode. The big knob in the photo above is
attached to a 100K ohm potentiometer, which is the tuning control.
Here are more details from the SWL website:
transceiver, 2.8 x 4.0" (7 x 10.1 cm)
board, masked and silkscreened
VFO: 35-40 kHz coverage
design, with crystal filtering
solid-state T-R switching (QSK)
Power Adjustable- 2.5W max.
Although I have had the rig on the air for only a few minutes
before preparing this article, I can tell that I will enjoy this rig and it
likely will be my main QRP rig. The receiver is very sharp and sensitive;
the rig is small and has low power requirement; and, all-in-all it's an
excellent piece of equipment.
More photos and modifications
Go to the next page to see more photos and modifications I made
to my SW+40