Both graphs display an odd hornlike spike at around power 240,000, implying an excess of radio frequency interference around that power. This goes against what we expect, since in theory there would be fewer spikes at greater powers. The horn could not be explained very well by radio frequency interference, however, since it seems to have a great deal of spikes at slightly lower powers, but virtually none past a cutoff power of roughly 265,000. In an attempt to determine the nature of these spikes, we investigated which frequencies contributed most to the spikes within the "horn".

Again, there seemed to be no explanation for the strange spike "horn" we had found. A standard emitter of radio frequency interference, such as a radar or satellite passing overhead, would tend to emit the high powered transmissions over a very small frequency range. As shown by the graph above, there was no significant correlation between the spike horn and any particular frequency, which ruled out much of the standard radio frequency interference. Although it is possible that a spread-spectrum satellite emitting over a wide frequency range could cause interference like this, a single satellite would not be over Arecibo long enough to result in as many spikes as were found.