Rick,
You can measure the losses with open OR shorted end with the MFJ-259. You
just have to make sure the other end has a "loss-free" short or open end.
(If you put a dummy load in the Loss Mode, you measure infinite loss, which
is a correct assumption with that method.) So if you just know that he othe
end of the cable is not connected to "anything" you will do OK.
Hans - N2JFS
In a message dated 2/5/2010 1:37:06 P.M. Eastern Standard Time,
richard@karlquist.com writes:
Jim Brown wrote:
> Not as ideal as you might think. The problem is that most coax is
> shipped on reels with access to only one end. To make a transmission
> loss measurement, you must unreel it to get a connector on both
> ends.
No, see below
>
> Now, if you happen to own instrumentation that allows you to measure
> that loss on a 1,000 ft spool from only one end, that's another
> story. :)
See below
>
> 73,
>
> Jim K9YC
I happen to own instrumentation that allows me to measure loss from
one end; it's called an MFJ-259B. Cable loss is a built in function.
As long as the far end is open, cable loss is half of return loss.
You can also calculate loss from VSWR. For example, 3:1 means your
loss is 3 dB.
Rick N6RK
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