K3ZQI/QRP

I enjoy operating low power and building receivers and transmitters to be used to work other amateurs using this mode.  QRP is generally thought of as being 5 watts or less, and most operators who use these power levels enjoy CW operation.  There are, however, many who use QRP for SSB operation on the HF bands with a great deal of success.

The first QRP transceiver that I built was a kit obtained from A&A Engineering.  That's probably the easiest way to get started or build your first "home-brew" equipment.  Back when I first became an amateur Heath Kit sold the DX-60.  I bought one of those kits and really enjoyed that experience, I used that transmitter to work Europe and South America on CW and AM phone for many years.  The only problem that I have is parting with the projects when I no longer desire to use them. The DX-60 continues to lurk in the attic, as it has for many many years.

After building the kit, I began to experiment with NN1G designs using NE602s.  Using that design I have constructed several transceivers for multiple bands.  These transceivers perform very well and I have had many hours of enjoyment operating this equipment.

QRP power lends itself nicely to other hobbies that I enjoy, such as camping.  I really don't mind chucking a home-brewed transceiver in my pack, along with a battery for power.  If it gets damaged on the trip, I built it and can generally fix it when I get back.  Most of the time I get to operate portable time and time again before I have that experience.

Antennas can be an obstacle when operating portable.  It's generally difficult enough to find the perfect location to set camp, let alone considering other factors such as where to erect the antenna.  For this reason I find a "small" antenna tuner to be a near must when operating portable.  There are many designs for QRP antenna tuners.  At the home QTH I prefer an SPC type tuner, for this reason I designed one which can be built for portable use.  Typically the heart of the SPC tuner is a variable inductance, a roller inductor is most often employed.  These components generally are large and expensive.  Not something you'd want to back around much.  In my design I have substituted a fix inductance per band.  Amazingly, even with the fixed inductance I am able to load into almost anything.  I've even built a multiband version for the home station and now use that one exclusively for QRP, leaving the B&W VS1500 for the QRO station.

The following schematic should provide enough information to allow you to reproduce this design should you desire:


Transmitter on the left connector and Antenna on the right connector.
  Turns required for  Lx
Band T-50-6
40 16
30 12
20 9
15 6
10 2
  For C1 I used a small single section capacitor of approximately 250 pFd. C2 is a dual section broadcast type capacitor of approximately 350 pFd per section.  Similar capacitors are available from Ocean State Electronics or Dan's Small Parts.  All toloids are wound with number twenty enameled wire.  Initially, I was soldering the toloids into the circuit as required, but now my breadboard model includes a single pole multi-position switch, S1, to "band switch" the tuner.  To feed open wire antennas I constructed a 4:1 balun using 15 turns of number twenty wire bifilar-wound on a T200-6 core.  I also tried a 1:1 balun, both achieved the desired result.  The T200-6 is probably a little bigger than your going to want to use for portable operation,  the one I use for the forty meter version is about one and a half inches in diameter.  Additionally, for a single band version you'll need only one of the inductors and eliminate the switch.

The SPC tuner is discussed in the ARRL Handbook, should you want to further investigate this design.  MAKE CERTAIN YOU HAVE A GOOD GROUND SYSTEM.  Sorry about the shouting, but I've found that a good ground system is key to achieving a good match.  I've used less than four foot of wire as an antenna and achieved a good match with this tuner, so long as I have a good ground. I generally attempt to get about sixty-five feet of wire in the air and an equal amount laying out along the ground.  It's easy to achieve a good match and yields plenty of contacts.

Thank you for visiting. I have provided a guest book for you comments.


Thank you.

CUL and 72s

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page last updated on April 2,2000