[Amps] Re: AMPS Link coupling

[Steve Thompson]

Ian White, G3SEK wrote:
> G3RZP wrote:
>>
>  >>Rich wrote
>  >>There is  no antenna matching network that has a lower Q than an
> L->>network.
>  >
>>
>> This is not correct. A parallel tuned circuit with a coupling  link,
>> loaded by a high impedance antenna can have its LC ratio determined
>> such as to control the value of Q. It is possible that self capacity
>> of the coil could be a limit in some cases.
>>
> Ignoring the unloaded Qs of the individual components from which a
> network can be constructed...
>
> The minimum possible *loaded* Q that is required to transform between
> two resistances R2>R1, using any possible circuit, is sqrt(R2/R1 -1).
>
> The L-network has exactly that value of loaded Q, so it is correct
> that no other network can go lower (at least for resistive loads; not
> sure about impedances in general).
Sketching it on a Smith chart, a quarter wave transmission line transformer
follows a locus with a lower peak Ql. Does that count, even if it's of
limited practical use?

Steve



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