SSTRAN tells us that the new model is shipping right now and is avaialialble in the same dependable configurations, with "10 kHz channel spacing for use in North and South America. Includes enclosure and 120 Volt AC Adapter. All surface-mount ICs pre-soldered to the board."
In telling us why this model can truely be called high efficiency, SSTRAN responds that "Transmitter range is a complicated issue that depends on the transmitter output power and the installation-specific antenna and ground losses. FCC rules limit the final RF stage power input to 100 mW. For any given antenna and ground system, the "best range" prize will go to the transmitter that is able to convert the largest portion of the 100 mW input power to output power."
"The efficiency of the RF output transistor is the first part of the overall efficiency calculation. Output transistor efficiency is a measure of the amount of input power that is lost as heat in the output transistor. The AMT5000 transistor efficiency is 98%, so only 2% of the input power is lost as heat."
"The AMT5000 has a built-in tuning coil in the form of an iron-powder core toroid coil. (The designer believes) Toroid coils offer major advantages over other coil configurations occupying the same physical volume, but only if the core material is properly chosen for the operating frequency and power level."
"In summary, the overall efficiency of the AMT5000 will be equal to or better than any other Part 15 transmitter utilizing an internal tuning coil, and the overall efficiency will be essentially the best theoretically possible when using any conceivable super-efficient, externally tuned antenna system." (© sstran.com)
Full specifications here: SSTRAN AMT5000 Specification Overview
Web Article here: AMT5000 High Efficiency Pro AM Radio Transmitter Kit