via HACKADAY: Pi Network Attenuators: Impedance Matching For The Strong Of Signal

If you catch a grizzled old radio amateur propping up the bar in the small hours, you will probably receive the gravelly-voiced Wisdom of the Ancients on impedance matching, antenna tuners, and LC networks. Impedance at RF, you will learn, is a Dark Art, for which you need a lifetime of experience to master. And presumably a taste for bourbon and branch water, to preserve the noir aesthetic.

It’s not strictly true, of course, but it is the case that impedance matching at RF with an LC network can be something of a pain. You will calculate and simulate, but you will always find a host of other environmental factors getting in the way when it comes down to achieving a match. Much tweaking of values ensues, and probably a bit of estimating just how bad a particular voltage standing wave ratio (VSWR) can be for your circuit.

If LC circuits aren’t for you and you have plenty of RF power to play with, there is of course another way to preserve impedance matching, and it’s one in which you’ll never have to tweak a recalcitrant inductor again. Simply use a resistive attenuator, and put in enough power to compensate for the fact that some of it will be lost as heat. Your impedances are set by resistor values, which are reliably available over a huge range.

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