Total posts : 45366
To test the AMT-5000, a 3 m vertical rod would have to be mounted in close proximity to the transmitter. The antenna mounting is not part of the design, and it would have to be improvised; but that would not be an overwhelming difficulty. Tuning would be done by selecting taps on the internal loading coil and using the internal tuning capacitor (C1) to tune for a DC current peak at the final stage. So far so good. What follows next is what I call “magic.” The instructions then say to turn C1 one turn clockwise, which is supposed to tune the transmitter below resonance by an amount that sets up class E operating conditions. Whether this particular tuning step works or not depends on what the ground loss resistance of the antenna installation is. The ground loss resistance for the installation is, of course, unknown, and can vary greatly from one installation to the next; and the operator following the manufactrer’s instructions does not know if his transmitter is operating class E or not. But the transmitter will “work” in the sense that it will produce an AM signal even if it is mistuned. What is unknown to the operator is if this transmitter is operating optimally, or “class E.” Optimum tuning requires observing and adjusting the shape of the drain pulse on an oscilloscope. Nothing in the instuctions tells the operator to use an oscilloscope or what to look for on the oscilloscope display. That is why I say that this design is best for the advanced experimenter rather than the general user.
As for using an external antenna with a loading coil that is described on the SSTRAN website, the transmitter design allows for bypassing the internal loading coil, but there are no instructions for tuning for a current peak as with the internal loading coil, and then adjusting for class E conditions. This is up to the “advanced experimenter.”