On Mon, 14 Jun 2004 05:20:37 -0700, Frank Gilliland
wrote:

In p7jpc05ugaf983cn5th32r7rd99cgvbh71@2355323778, Lancer
wrote:

snip
Wrong, the coil has very little radiation. The open air coil has less
loss because the losses are less in an open air coil.
(resistive losses, capacitive coupling losses, form loss)
Do a search on coil Q

Care to argue that point?


I would. What happens when you bring a solid sheet of conductive
material close to the end of a coil? Eddy currents -- it has
tremendous losses, the Q drops like a rock, and it's inductance is
unpredictable. It's a royal bitch to design a shielded IF/RF coil or
transformer to be used for high frequencies, and shielding is almost
-never- used for power RF coils and transformers unless there is some
serious space between the inductor and shield, hence the popularity of
toroid cores for those applications. And since a bigger coil makes a
bigger field, you need much more 'free space' to maintain a high-Q.
Vertically mounting a big coil above the sheet metal of a vehicle
results in a very lossy coil.


I would think that 4 feet would be more than enough distance.
So you would say that a large air wound coil has more loss than a
small diameter coild wound on a solid form?