Just seen this thread.
Trying to decipher a photographed TDR trace is pretty awkward, to say the least. What I would say though, is you are correct about getting the gain correct.
With the gain pumped up, you can have a circuit look like the backdrop of 'The Alps', even though there is nothing wrong with the circuit. As has been mooted, cable poundage changes also play a great part in what the TDR is looking at. As I haven't used one of those devices for donkeys years,(HAWK and JDSU for at least 8yrs now), I forget how the screen-shots progress, but I would view the screens with the auto-applied dB gain, then decrease the gain to see how it looks then. A prevalent HR will still be visible even on a low gain.
There really is a lot to consider when looking at traces, especially on miniscule type faults. If its a full-blown short circuit, or a cut cable .... then happy days, TDR will home in on it in a breath. But developing faults are a different story, depending on the severity the fault.
I've mentioned this before but just for you ....... I would personally lose the 76mtrs of cable you have applied (a very odd ammount might I add ??
), and connect straight into the test socket. Ideally, the connection would be onto the bare wires, but rules & regs prevent this
. Now, with the TDR running I would ring your landline number and watch the trace for increases/decreases in peaks/troughs, As the ringing voltage is approx 90-120Vac, it puts more stress on the circuit than the nominal 50Vdc it would be under when you have your TDR connected.
If there are any faults brewing, there's a probable 80% chance this trick will highlight where they are. You have to have good eyes to scan the full range, but I've found many a HR using this trick that all the other testers miss ..... PQT/Eclipse/DSL Close-out etc etc ....
In a nutshell though it is as with most things, experience and knowing your own meters nuances that allow a good decision to be made on TDR traces. Believe me, if you're going to request traffic-lights and a 'dig' from our contractors (ie- a lot of money), then you dont want the outcome to reveal a damned poundage change, whereas you thought it was a HR fault on the TDR. Been done many, many times ........ but not by me.