Ian White GM3SEK wrote:
> An L-network only has two variables, so the working Q is automatically
> determined for you. With a resistive load, this is automatically the
> lowest that can be achieved - so that is an advantage. The only case
> where an L-network won't give the lowest possible Q is with certain
> highly reactive loads... in which case, you need to switch to a totally
> different configuration of L-network.
I disagree. I haven't time to try and remember how to do the maths, but
looking at a Smith chart, I think a three element network can give a
lower loaded Q if there is any reactance in either impedance. The
difference might be minimal when the reactance is low, but I think it's
> This last point is the major DISadvantage of L-networks: lack of
> flexibility. There are a total of 8 different configurations, and they
> all have a limited matching range. Between them, they can match any
> impedance (except a 1:1 match requires theoretically zero or infinite
> component values) but it's a matter of finding which one out of the 8,
> and most practical L-network tuners can switch between a maximum of 2
> configurations. However, I'd conjecture that for any pair of
> impedances, there will always exist at least one L-network configuration
> that can match them at the lowest possible working Q.
I think not, except for the particular comparison of L against three
element matching between two pure resistances.
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