New beacon weaker than the old one ?? - Read on

The new beacon is running at 30 watts output compared to the 40 watts output of the old unit. This difference of only -1.2 db should make no perceptible difference under the same propagation conditions. However, if you think that the new beacon is weaker than the old unit then Andy G4JNT explains……

The claims of it being considerably weaker are almost certainly a psychological effect of only receiving the tone for a little over one minute out of two. If they are happily listening to CW and a steady tone at their preferred frequency, the ears are operating at an effective bandwidth of 10 - 50Hz. After making some S/N measurements, I measured my ear/bio-DSP combination at around 20 - 40Hz, but only over a very small preferred tonal range - for me that is around 600Hz. If there is any change in tone frequency away from the optimum, apparent S/N plummets.

And that's what it is like listening to a weak GB3VHF signal. By putting 20 - 25dB of attenuation in the antenna feed for an average received signal strength, I can reduce the received signal from quite CW-readable to something that takes several WSJT averages to give the message and is not audible. Given the right tuning point, time of day, lighting, background noise, alcohol intake etc etc, the tone is detectable by ear at 15dB attenuation, although I haven't a hope of copying CW at that S/N. So, as soon as the JT65 signalling starts, the audio appears to fail completely. Such a drop would easily be interpreted as a much weaker signal than before, and even when it reappeared, 49 seconds later, the psychological effect of its going will dominate.

Wonder if there are any psychologists / audio experts who are interested in weak signal listening and low S/N auditory phenomena, who could take this idea further and devise some real experiments.

Andy G4JNT