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[TowerTalk] power ratings for antennas

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Subject: [TowerTalk] power ratings for antennas
From: Jim Lux <>
Date: Mon, 20 Apr 2015 09:24:58 -0700
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I'm not sure how they develop power ratings in the first place. As VE5RA commented, I'm sure it's marketing and experience, as opposed to formal engineering processes. That is, I doubt anyone is building a FEM thermal model, or looking at convection and conduction to the surrounding air, analyzing the current and voltages in traps, baluns, or chokes, etc.

It's more a "we built an example, and we put X watts into it, and it seemed ok, and it seems it should take twice that, so that's what we claim."

There's also so many variables on what the power limit might be. Someone running 10 minutes of RTTY at 1500W is very different than someone doing SSB DX contesting at 1500W.

In some cases, I think, too, what you're seeing is a translation of power to some other parameter from construction guidelines. I can see some old QST article saying "for 1000W AM, make sure you use AWG 12 wire"...and then they wire the thing up with AWG 12 and call it "rated for 1kW AM"

What you're not going to see in the amateur world is specs of the quality used in commercial/industrial work. For instance, at JPL, we use "analysis shows 10dB margin or test shows 6dB margin" (e.g. twice the expected voltage and current in test).

And I'm sure someone buying high power RF systems for plasma etchers or broadcast systems is seeing "real" specifications with test data and/or analysis to back it up, if not an actual production line acceptance test at the rated levels.

In the amateur world, though, it tends to be more anecdotal. "someone built it and it worked at least once at this level"

Which is good: it means that amateur gear is MUCH cheaper than gear with all the test documents and analysis.


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