2017-05-20, 23:49
I like that variable distance from events resulting in the observations of the events getting jumbled. Something I hadn't twigged about a real world TOA system...
They are a strange signal but the spectrum plot reflects the impulse so I'd say they are real. As a check do they stop if you short the head amp loop inputs? How is the H-field head amp connected to the loops?
The other thing to note is that they are *BIG* signals, I've seen the peaks clipped off at something over 2.4 V peak to peak. The Y scale on many plots automatically scales itself to the size of the impulse, so what appears to be a similar sized signal can actually be very different. The fourth Y marker away zero on your plots varies from 0.08 V to 1.2 V. These "smooth" signals vary in amplitude from only occasionally 0.6 V P to P to overloading the amplifier at > 2.4 V P to P. Most "normal" signals are less than half that minimum, 0.16 to 0.3 V P to P.
As BobW says watch the "noise floor" display on the receivers Signals page and see if there is any sort of pattern or regular repetition. If they aren't very frequent getting a bearing from a loops null might be rather time consuming. On my 30 cm 20 turn loops the null is very deep but also very narrow. A tiny rotation, just a degree may be two, can take you from one side of the null to the other and with the amplitude varying anyway...
They look like switching impulses but can't think of anything that switches a fair amount of power (due to the signals size, unless it's very close) at what appears to be tens of seconds or a minute or two intervals.
They are a strange signal but the spectrum plot reflects the impulse so I'd say they are real. As a check do they stop if you short the head amp loop inputs? How is the H-field head amp connected to the loops?
The other thing to note is that they are *BIG* signals, I've seen the peaks clipped off at something over 2.4 V peak to peak. The Y scale on many plots automatically scales itself to the size of the impulse, so what appears to be a similar sized signal can actually be very different. The fourth Y marker away zero on your plots varies from 0.08 V to 1.2 V. These "smooth" signals vary in amplitude from only occasionally 0.6 V P to P to overloading the amplifier at > 2.4 V P to P. Most "normal" signals are less than half that minimum, 0.16 to 0.3 V P to P.
As BobW says watch the "noise floor" display on the receivers Signals page and see if there is any sort of pattern or regular repetition. If they aren't very frequent getting a bearing from a loops null might be rather time consuming. On my 30 cm 20 turn loops the null is very deep but also very narrow. A tiny rotation, just a degree may be two, can take you from one side of the null to the other and with the amplitude varying anyway...
They look like switching impulses but can't think of anything that switches a fair amount of power (due to the signals size, unless it's very close) at what appears to be tens of seconds or a minute or two intervals.