Electronic – Time domain reflectometry (TDR), pulse shape

cablescoaxsignaltdrtransmission line

Considering this coax cable open end reflection. What are the correct explanations for the flatter rise time, the rounding of the first reflection, and the much smaller what I assume to be secondary reflection?
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EDIT:

Cable: ~100m 50ohm "m17/028-rg-58"

Scaling is 500ns/div.

Signal: 100kHz square wave.

EDIT 2:

Suggestion:
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EDIT 3:

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Best Answer

The slower edge in the reflection indicates that high frequency signal components are in the reflection are attenuated compared to the low-frequency components.

The main reason for this is likely that the coax is lossier for the high frequency components than for the 100 kHz fundamental. A chart I found online indicates typical RG-58 has 6.6 dB/100 m loss at 30 MHz, and 16 dB/100 m loss at 100 MHz, for example. Remember that your reflected signal passes through the cable twice (so you need to consider 200 m worth of loss) when using these figures.

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