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[Towertalk] SteppIR Power Handling

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Subject: [Towertalk] SteppIR Power Handling
From: (Tom Rauch)
Date: Sun, 28 Jul 2002 12:47:44 -0400
> Originally, Rick said:
> > > I just noticed the power handling spec for the SteppIR antenna -
> > > "2kw PEP."  Has anyone used it with 1.5kw CW?
> >
> Have I been away from ham radio too long??  First "no code" and
> now.... 1500 watts legal plate power input???
> What am I missing here?

You are not alone Gary. I received about a dozen e-mails from people 
who are confused! 

The old limit was either 900 or 1000 watts dc input measured on 
meters with a specific response characteristic. That was the limit 
both on SSB or CW. It worked out that the dc input, for the highest 
meter swing, was somewhere roughly around 2000 watts of peak dc input 
power....but even that number varied wildly with voice 
characteristics. The real limit was 1000 watts DC (or 900 if you 
could not read HV and current at the same time) MINUS the driver 
power if the PA was grounded grid.

The new limit (new around 1980 anyway) is 1500 watts peak envelope 
power output on most modes in most operation. Certain bands (like 
WARC bands), some modes (like AM), and certain station locations 
(like those near the Canadian border on some frequencies) can have 
other power limits.

A good CW signal has a peak envelope power equal to the sustained 
power you would see on any meter. 1500 watts PEP SSB output is equal 
to 1500 watts steady CW carrier output, unless you have a bad rig 
with envelope ripple or overshoot (there are several radios sold like 

An average power of .0001 watts for an hour can be 1500 watts PEP (or 
less), but an average power of 1501 watts would always exceed 1500 
watts PEP. None of this has anything to do with .70 or 1.414, or 
anything else like that.

It actually is a more simple and direct method. You just can not 
exceed 1500 watts of peak envelope power, with envelope power defined 
as the RMS power of each individual RF cycle.

73, Tom W8JI 

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