[Amps] Acceptable Swr for a tube amp without retuning.

[jim.thom jim.thom@telus.net]

>So could someone please explain or point me towards some books/articles
>that talk about what happens exactly with voltages/currents at bad SWR?

To keep it real simple, depending on coax line length, ( node /
anti-node),  the max voltage =  sq root of the swr. IE: 2:1  swr.   Max
voltage = 1.41 x normal (1:1 swr) swr.

1500 watts into 50 ohm  dummy load =   5.5 amps into 50 ohms  = 275 Vrms =
386 V peak.
With a 2:1  swr,  rms voltage will rise to  386 vrms.  Peak V will rise to
550 V peak.

Max  rms current  will also be sq root of  the SWR.  Into a DL, that's 5.5
amps with 1.5 kw and 1:1 swr.

With a 2:1 swr, RMS current rises to 7.78 amps.

You will not obtain max V  or max I at the same time.

It's average current that melts stuff.....and peak V that arcs stuff.

Depending on power output, with typ tube amps, I would not go much past a
2:1  swr.   Maybe 2.5:1  max.