Re: secondary harmonic suppre
Richard Craven wrote...
> In a standard helical resonator the device is a quarterwave
> long and can be link or loop coupled (see the ITT databook
> for a section). The problem is that such a resonator "throws
> back" at harmonics by which I mean that a band pass filter,
> for example, will have good out-of-band attenuation except
> at harmonics of f (2f particularly so in elliptic designs).
> The point is that there is a technique where the top third
> of a coil is wound in the opposite direction to the first
> two thirds. It struck me that it might be interesting to
> wind a TC resonator such that the top third is reversed.
> Apparently, if you do this, the harmonic response at 2f and
> 3f is dramatically suppressed and the first significant
> harmonic occurs at 4f, by which time the amplitude is well
> down cf. the fundamental.
I'd be keen to try this when time permits. Is this the folded
resonator concept you mentioned once?