Time Domain Reflectometry

You only need matched termination for when the pulse returns, by wich time the transistor will be fully off.

ofc this rules out using a step.

Most ethernet chips have TDR built in for coax connections anyway, even most PC ethernet ports have this feature, although its probably quite hard to find any software that can access it.

Another good way is to use a single frequency at anyone time, and measure the standing wave voltage, thus avoiding any pulse smearing, to give absolute distance the frequency is scanned untill it passes through

all it needs is a 1-2ghz vco and a PIC.

Colin =^.^=

The absolute-max ratings aren't your concern here; the design uses multiple outputs in parallel to ensure that the output impedance of the 74AC14 is NOT limiting the current; that output impedance is not even remotely constant through a transition from high to low, or from low to high, nor is the low impedance the same as the high impedance (remember, those impedances result from very different transistors in the chip). The only problem with this is that a lot of gates on the chip are transitioning at the same time, and your power supply pins will require the best bypass capacitors and wiring that you can arrange or you'll get power-supply-droop.

If your drive is higher impedance than the 50 Ohm cable, the capacitance dominates and you get low-pass characteristics. If, on the other hand, your drive is LOWER impedance than the cable, the series inductance dominates and you get high-pass characteristics. If you match the impedance, you get neither.

'Neither' is the right answer here, because it simplifies the resulting behavior. You were looking for another effect, nicht wahr?

Ahh - the memories ... I dropped one out of the back of a van once doing some rental car driving on a gravel road ;-) Good thing we shelled for the transport ca$$$e - instant ROI!

another kiwi!

most of the world won't get those. the usenet network has strategiically located filtering software that strips them out.

You should have access to alt.binaries.schematics.electronic where they are allowed.

Bye. Jasen