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Michael A. Terrell Michael A. Terrell is offline
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Default Need help - no signal from TV antenna in the attic - ContinuityTest?


mm wrote:

On Mon, 08 Dec 2008 12:32:14 -0500, "Michael A. Terrell"
wrote:


mm wrote:

On Fri, 05 Dec 2008 15:07:46 GMT, "TKM" wrote:


Who knows if it's OK to measure the resistance (using a standard multimeter)
of a coax line connected to an amplified antenna after disconnecting the
amplifier power supply, but not the antenna. I'm concerned about damaging
the amplifier inside the antenna,

You want to measure the resistance of the center conductor, right?

Easy to connect to the coax, but what do you want to connect to at the
other end? The rods that stick out of the antenna?

The voltage from a multimeter, 9 volts usually, isn't going to hurt
anything, but I don't think you can expect a meaningful measurement
either.



What kind of meter are you using with 9 V between the probes?


Well it's been decades since I measured the voltage, if I ever did, so
let me just say that the voltage will be NO MORE THAN the 9 volt
battery provides. It might be less, but there are no voltage raising
circuits in a "standard multimeter", which the OP plans to use.

Ohm
meters are usually current limited, or constant current sdesigns.


How would knowing this help him? His concern was about damaging his
amplified antenna.



My point was that the ohm meter was designed NOT to damage solid state
electronics, unless he is using a pre WW-II meter with a high test
voltage & current. A few old meters were still in shops when the first
transistor equipment hit the market. the service manuals warned you not
to use the outdated equipment, or you would destroy the transistors.


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