As les-70 has mentioned, at a quick glance, that Hlog curve does look more or less normal.
However when I plot that data at an identical scaling to my own, "oddities" are noticeable. See the first graph, hlog-20140406-1501.png, below. Note how that a large proportion of the curve is off the Y-axis, below -100 dB. Re-plotting the curve, giving the Y-axis further 50% in its scale, results in the second graph, hlog-20140406-1502.png, below. We now see that, in general, the overall shape of the curve is reasonable but the attenuation, across the entire range is higher. I wonder if loading's circuit makes significant use of aluminium cabling?
Two anomalous regions are the frequencies used by the US band and the spike centred at tone 144 (~623 kHz). The former can be rationalised by power cut-back, etc, as we see that loading's US synchronisation speed is capped to 448 kbps. As for the spike at tone 144, I do not know.
