W4BXI Test of 5 Antennas

Here is a screen shot of audio recorded at about 0835 CDT at my receiver during W4BXI's test of 5 antennas on 3740 kHz. The total time duration is just over 50 seconds. Today I had the RF gain set to max, where the S-meter readings are most 'accurate'.  Yesterday I had it set some amount below max during the audio recording. Having the RF gain at max may alter the receiver's AGC action and resulting amplitude comparisons. I note that the background noise rises in amplitude before each tone transmission starts.For future audio recordings I'll make a point of reducing the receive RF gain.

W4BXI Antenna Traces

Here is the audio waveform recorded this morning on 75 m at WA5MLF during W4BXI's test transmissions on four different antenna configurations. The effects of signal fading (QSB) can be seen during each transmit period. The elapsed time shown is 21.55 seconds. The recording and waveform display are from CoolEdit2000, but the same features are available with the free program Audacity. 

Tim WA4PTZ also made an audio recording at his station. He captured the last 3 test transmissions. Below is a dual-trace display with Tim's recording on top and WA5MLF's recording below. The elapsed time is 17.9 seconds. Click here for an mp3 copy of the composite recording.

The upper waveform gives the appearance of a steady signal from W4BXI for each tone (carrier) transmission, but it is not known how much the AGC in Tim's receiver or PC sound card affected the recording levels. Note that the noise level after each transmission rose to a level with peaks similar to the level of the steady tone (carrier).

John