[TowerTalk] Coax Loss -- RG-Numbers Don't Tell us Much

[HansLG at aol.com]

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 at 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
_______________________________________________



_______________________________________________
TowerTalk  mailing  list
TowerTalk at contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk