Kit by EMTECH - Built by Steve, N9OH
I built a ZM-2 QRP Antenna tuner on 11-Apr-2003. It took only a couple
hours to put together and was very simple. The longest part was waiting
for the acryllic paint to dry! (see below) The neat part about this is
the LED indicator for SWR. You actually tune the caps until the LED
goes out (turns off) and that indicates a 1:1 match! Its very sharp and
requires no power -- it gets its power from the RF! Its switched out of
the circuit by a tune/operate switch.
First we unpack the components. There aren't a lot! In fact, most of these
parts look like they came directly from Radio Shack. I'm sure they did.
Starting to wind the first toroid. This is actually the first toroid i've
ever wound, so don't laugh.
Some more windings....
Now the first toroid is finished. Notice the various connections.
This very small toroid is not only hard to see because of its size, but its
also hard to see because my digital camera sucks. I used #28 magnet wire
to wind this toroid, and it is used in the SWR measuring circuit.
The metal plate came pre-drilled, but the printing is actually a label
that was printed on a laser printer and I had to line it up and stick
it on myself. I decided to use some acrylic sealer (3 coats) to protect
the face plate and to keep the labeling from rubbing off after light use!
Here i created three 50-ohm/4-watt resistors. The kit came with 100-ohm
2-watt resistors and this gives us the correct resistance and handles more
power. The tuner is rated for 15-watts in the "operate" position, but at
tune-up it can't handle more than 4-watts for more than a few seconds or
else those resistors get HOT!
Here's the front panel with some of the hardware installed. Note the long
shafts installed on the two variable capacitors.
And here is the back of that front panel, showing some of the mounted hardware.
Another shot of the front panel with the big knobs installed!
Same thing here... but notice i installed the SWR-indicating LED in a
small rubber grommet.
Some point-to-point wiring on the panel...
And now i add the resistors and the small toroid...
Things are coming together now with the big toroid wired in place.
The wiring of the toroid actually holds it in place with its short leads!
Its together! The first view of the ZM-2 in its case. Screws still missing
just in case I need to make some internal adjustments.
There it is! It worked the first time I hooked up a radio. Here i easily
tuned a length of speaker wire to operate on 30 meters.
And one more final view of the tuner in all of its glory.