The motivation for this was the test of non 100 Hz PRF (e.g 8192us IPP) which showed that AGC=4 is unusable in the presence of PRE/Digisonde interference because this interference sets the attenuators too high in the absence of valid echoes, whereas the simple AGC=1 ignores the background interference level and gave better results.
The results are summarised in the EXCEL spreadsheet which includes a plot of the
results. I used the size of the soundings as an indicator of the number of echoes.
Of the 84 pairs of soundings, the average ratio of the sizes of soundings with
AGC=4 compared to AGC=1 is 1.45 (with a st dev of 1.15) showing that on average
we get more echoes with AGC=4.
The plots are interesting though, because there are times when the ratio is less than 1. The ratio is also largest when the number of echoes is smallest, presumably
at night when there are many interfering stations and weak echoes.