[TowerTalk] Relays for High Power

[Bogomir Rejc]

> I am looking at some Potter Brumfield relays/switches to remotely switch in 
> loading at various antennas.  At a KW output, what should the rating of the 
> contacts be on the PB relays?  Will 5 amps be adequate?

Voltage and current maximums on lossless lines are calculated 
using  the following equations

Emax=SQR(P*Zo*SWR)
Imax=SQR(P/Zo*SWR)

where SQR is square root, P power and Zo characteristic 
impedanc.

Assuming 1500W, 50Ohms and SWR=3 this would give 474V and 
9.5A.

Values calculated using the above equation are maximum 
expected values. Losses in line tends to decrease these values. 

So for legal output 5A under missmatch conditions wouldn't be 
enough.

Does anybody know how RF current ratings are related to usualy 
specified 50/60Hz ratings?

73s, Mirko, s59x

----------------------------------------
Bogomir Rejc, S59X
Platiseva 25
5282 Cerkno
SLOVENIA
AX.25: s59x@s50box.svn.eu
Email: bogomir.rejc@eta-cerkno.si


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