Carl's antenna comparisons

Carl's posting provided a recording of HF receiver audio while switching every 10 seconds between two different antennas. Since the audio level on the first antenna was a bit lower than the second, I thought it might be helpful to make the two cases approximately equal for a better listening comparison. Below is my software's view of the edited recording, with the 1st, 3rd, and 5th segments boosted by 40%. A copy of the edited recording is available here.

My impression while listening to this copy of the audio is that the 2nd segment has slightly stronger voice audio but with background noise that has more of a power line noise character.



Using my copy of the Cool Edit software I ran some Fast Fourier Transform analyses on the edited copy of the recording as well as the original. A transform of the complete audio recording, based on 8192 points, is displayed in the graph below.



Transforms of the 1st segment of audio (antenna 1) and the 2nd segment (antenna 2) looked fairly similar. Let me know if you'd like to see those graphs.

Due to the varying frequencies and levels of the voice, it was not possible to pick out its characteristics easily from the broadband background noise. A better test would be to transmit one or more steady audio tones and record the received results on the different antennas for comparison using the FFT analysis.

John