Friday, September 25, 2020

Building the Emtech ZM-2

Although not a transceiver, I consider the Emtech ZM-2 a QRP classic. Years ago, Emtech did sell transceiver kits - the NW20, NW30 and NW40.

I never built any of their transceivers but I did build a ZM-2 tuner long ago. At the time, they only offered SO-239 connectors and mine always had SO-239 to BNC adapters on it to accommodate the rigs I used with it. Also, my construction in those days left a bit to be was time to build a new ZM-2.

ZM-2's are now available in kit form or already-built, with BNC's or SO-239 connectors.

Over the years, I've come full circle on the topic of internal autotuners - at first, preferring them - vs. outboard manual (or auto) tuners. The KX2 was the first rig I had with an internal autotuner and I loved its convenience. With other QRP rigs, I used Elecraft's outboard autotuner, the T1. So I sold my original ZM-2.

But I always cringed a bit when the T1 cycled through its coils and caps in search of a tuning solution. The rigs, for brief periods, were exposed to very high SWR's and some rigs are quite sensitive to the voltages presented during these sweeps.

So I'm back to needing an external manual tuner for QRP outtings, thus the new ZM-2. With the ZM-2, a tuning solution quite close to optimum can be found without even transmitting, just by listening for a peak in receiver noise.

And, as any ZM-2 owner will tell you, they'll tune just about anything.

The kit of parts arrived in about 10 days and included printed instructions and two decals. I needed both decals because I goofed on applying the first one and it was off-center. The instructions are supplemented by numerous photos on Emtech's website and by a very helpful video that suggests an easy way to build a diode-LED-resistor network.

Everything about assembling the kit is straightforward with good, clear wiring diagrams. It will be more difficult if you're fat-fingered, especially when installing the smaller of the two toroids.

Despite a less-than-perfect construction job, it is an improvement over my 1.0 version.



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