L matching network

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WA2SQQ:
For a simple L matching network I’m going to use for a 160m inverted L, is there any difference if I feed the RF into the inductor, with the capacitor after the inductor to ground, vs. feeding the capacitor with the inductor to ground?

Also, to handle 1kw, what would the recommended voltage rating be for the capacitor?

N1BCG:
It depends on the impedance of the antenna at the feedpoint and that will determine whether the component to ground is at the xmtr or antenna feedpoint. Once you know the impedance you can calculate the voltage and current throughout the circuit to determine component values.

Also consider that the series inductor with shunt capacitor to ground will act like a low-pass filter and have better harmonic filtering characteristics than if the components were swapped.

The short answer would be: "depends"

K1ZJH:
Do you have an antenna analyzer?  What is your feedpoint impedance? If low, you can lengthen the antenna and use a series cap to increase the impedance at the base. That will also elevate the high current point on the vertical portion of the L antenna. Inductors are in general more lossy than a good quality cap.

http://www.eham.net/ehamforum/smf/index.php?topic=111769.0

Pete

WA2SQQ:
Thanks - the project begins next weekend. I’ll have some numbers to work with.

W3RSW:
Capacitor shunted to ground after the coil feeds a higher impedance antenna than the radio's 50 ohm output.

Capacitor shunted to ground before the coil feeds a lower impedance antenna.

Typically a L network tuner will have a switchable stator on the capacitor from
both the input side and the output side, the rotor of the cap being grounded.
Be sure the switch can carry high current and voltage and is not far from the
input and output terminals with short as leads as possible to the cap.

As an example if the antenna is a little shorter than natural resonance, a few turns of the coil will load it with the capacitor cancelling additional reactance.  

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