Barry wrote:
wrote in message
...
spamhog wrote:

A good time-domain reflectometer

Thank you Barry! Would TV/FM transmitter and cell BTS installers
normally have such a device? I don't know any ham who has one but
these days I am talking to professional antenna people. And, by the
way, if one thing I am working on pans out, they'll come to install a
BTS right atop my condo. (The challenge will be to convince them to
let me hang HF wires from the same tower :-)

If you have an oscilloscope, a pulse generator and a calculator you
have
a TDR.

If you don't have a pulse generator it takes about 2 IC's to build one.


--
Jim Pennino


You would need an extremely fast rise-time pulse generator and an
exceptionally fast oscilloscope to match a typical commercial TDR.

Yeah but in the real world you don't usually need to match a commercial
TDR to find a fault.

Back in the days of ethernet over RG-58 I was able to find lots of poorly
attached connectors and cables crushed by the electricians that installed
them (there were no network engineers and installers in those days) with
a 100 MHz 'scope and a pulse generator made from a 555 timer and a 50 Ohm
line driver.

The accuracy of the measurement for fault finding doesn't need to be much
better than a few feet to be able to find the fault visually once you know
about where it is and faults at the end are immediately obvious.

If the task is to find faults, a 'scope and simple pulse generator works
just fine.

If the task is to certify 6 inches of hard line to GHz to some mil-spec, you
probably want something more sophisticated.


--
Jim Pennino

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