[TowerTalk] In Search of 2db

Tom Rauch W8JI@contesting.com
Fri, 26 May 2000 22:44:16 -0400


> >   Query. I have a two radio station with a lot of 50 ohm jumpers. It
> >  works, honest. But some jumpers were assembled in the middle of the
> >  night by tired operators. Some are 30 years old.  I doubt any of them
> >  was done as well as W0UN or KC1XX would do it at his work bench. No
> >  jumper is longer than 10 feet. See configuration below (which should
> >  look similar to a lot of stations). What method do you recommend to
> >  test RG-213 or RG-58 jumpers? Any chance I can pick up 1 dB by finding
> >  a "bad" jumper? 

Let's see, -1 dB is 20% loss. The power lost turns to heat. 20% of 
1500 watts is 300 watts. 300 watts of heat in ten feet of cable is 
2.5 watts per linear inch. You won't need a meter to find that loss!

If you run low power, you'd need to measure the loss with a meter. 

If you run high power, you can use a smoke alarm to test the cable.

The only real worry with short jumpers, unless they melt, is if the 
have ingress (signals leaking in) and egress (signals leaking out). 
I'm still using jumpers I made up in the 60's!





73, Tom W8JI
w8ji@contesting.com

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