I wrote to the webmaster of the HIPAS site http://www.hipas.alaska.edu/hipasweb/hipas.htm and they have improved the description of their transmitters: The Heater system consists of 8 transmitters capable of conducting amplitude modulation of 100 Hz - 20 kHz and phase modulation of 0 -20 kHz. Each transmitter can transmit up to 150kW at 2.85 or 4.53 MHz on CW mode. The HAARP transmitter is also in the HF band (3 - 30mHz), so neither is anywhere close to 17 Hz! I think a 17 Hz transmitter and antenna need to be quite different from HF far-cousins. In fact I'm having a hard time imagining a 17 Hz directional antenna in Alaska since the wavelength is 18,000 kM. CO2 is only .04% of the atmosphere by volume. Maybe the laser can be tuned to heat CO2. And then, maybe a heated column of CO2 can be a major absorber of 17 Hz radio waves even with an omnidirectionnal transmitter? I only watch EE from the sidelines. --Steve