Re: Homebrew traps

Richard Clark wrote:
. . .
No, you don't need expensive 6KV caps unless you put the wrong
frequency to the antenna - and by wrong, I mean wrong band, not just
slightly up or down band.

The voltage across these traps (with all presumptions being observed)
will vary from 400V to 550V across the 40M band for an ideal antenna
in free space. You probably live on earth, so presumptions are
already beginning to shift.

There are quite a few variables involved in determining how much voltage the traps will see, not the least of which is the L/C ratio of the trap. I dug out a model of a 40/20 meter trapped dipole using traps using RG-58 I did some time ago, and found the trap voltage to be 568 volts RMS with 100 watts at 14.0 MHz. That's 800 volts peak. A model of a 40/20 meter trapped dipole with trap component X = 1000 ohms at resonance and moderate inductor Q showed highest voltage of 648 RMS (over 900 volts peak) at 7 MHz. So I'd want to use capacitors with a 2 kV rating to provide some margin.

Roy Lewallen, W7EL
.

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