thumper wrote:
I notice very few enclosures; most sets are ectomorphic. Is this the choice of the builder, or do sets operate their best when nothing separates components from the air?
All substances have a quality called dielectric constant. A coil in free space, far from any other matter, will have a higher Q than one in proximity to other objects. The inverse-square law is in effect here: Doubling the distance between the coil and other objects reduces the effect by the square of 2.
The Q-spoiling effect of adjacent matter depends on its dielectric constant. A 4- by 4-inch piece of aluminum two inches from the coil will have a greater effect than a piece of Lucite the same distance away.
Variable capacitors with ceramic insulation perform better than those with Bakelite or plastic insulation, due to reduced leakage resistance. If you place a shield or cover too near the capacitor, you may introduce a secondary leakage path. If you're using an inexpensive cap, the effect will be less measurable.
In the case of a set like Mike Tuggle builds, I suspect he either puts it in a box when not in use, or covers it some other way, only exposing it when he's listening. As krystallo noted, dust on the plates of a variable cap will reduce leakage resistance. For Mike's sets, which are built on separate boards, being able to see the components must help when moving them around.
Then there's the aesthetic experience. Many of us, who are less skilled and patient than Mike, use enclosures so we don't have to look at the haywire.
For a beginner's set, where you're using less-than-best components, this is not so important, as the components themselves set the upper limit for performance. At the higher levels of crystal-set design you have to resort to extreme measures to gain any further improvement in performance.
73,
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As often everyone has to find its personal compromise depending on the own wishes.
