NO you cannot use an ohmmeter to measure (RF) signal loss. First you must
determine what frequency you are going to use. Calculating the loss is the
most common way. Manufacturers provide graphs or tables of frequency vs
length. This is the only way we in the broadcast field use to determine
loss. It's almost impossible to accurately measure the loss of a 100mhz
transmitter feeding a 1200 ft run of 3 inch air dielectric heliax at the
base of the antenna. The FCC only requires a calculation of loss for this
purpose. Loss is measured in either db or %. i.e. 3db loss = 50% loss =
gain of .5.

Since you mentioned RG6 or RG11, it can be measured even if you don't know
the length. Obviously you're interested in a given frequency (band). One
way is to use a low power transmitter matched to one end of the cable via
a wattmeter at the cables impedance. The other end through another
wattmeter to a termination resistor matched to the cable impedance. Lets
say the transmitter is outputting 5 watts. Anything less than 5 watts will
be your measured loss at that frequency. To calibrate your setup, just
leave out the transmission line and both meters can be checked for 5 watts
each.

Another way would be to use a calibrated signal generator at one end and
an RF test set at the other. Impedance matching and termination must be
taken into consideration. Loss can be accurately measured in db from the
RF test set. The obvious drawback is the cost of the equipment in this
setup. Approx. $8000.00 unless you have access to a two-way radio shop.
The former procedure would cost in the neighborhood of about $1000.00.

As you can see, calculating the loss will cost you a pencil and paper and
a look at a graph. :-)
http://www.radio-ware.com/products/techinfo/coaxloss.htm
Rick

Chris Carbaugh wrote:

> Hello all,
>
> I'm looking for a method to measure signal loss (db) on RG6 and RG11
> coax cable.  I think I can do this with just an ohm meter, but I'm not
> sure how to cap the opposite end.
>
> What I'm trying to accomplish is to (1) calculate the actual loss on a
> coax run, and (2) calculate the length of the run by comparing signal
> loss to the specs from the manufacturer.
>
> Most coax manufactures (I believe) specify signal loss per foot.
>
> Any help greatly appreciated,
> Chris
>
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