On Wed, 24 Sep 2008 19:25:37 +0100, Graham. wrote: > But a wooden dish?
How about using trees as antennas?
From
Abstract : Communications over short ranges through dense wooded or jungle terrains remains a major problem for our armies today. An approach to solving this problem is to use a Hybrid Electromagnetic Antenna Coupler (HEMAC) toroid as a transformer-coupler to excite secondary radiation from the vegetation. The combination of the electric and magnetic fields emitted by the toroid are shown to be as effective as a whip antenna for communicating in the wooded areas adjacent to Fort Monmouth. Initial experiments comparing a HEMAC toroid to a whip antenna are discussed. (Author)
And a Scientific American article at
QUOTE
It is not a joke nor a scientific curiosity, this strange discovery of Gen. George O. Squire, Chief Signal Officer, that trees --- all trees, of all kinds and all heights, growing anywhere --- are nature's own wireless towers and antenna combined. The matter first came to his attention in
1904, through the use of trees as grounds for Army buzzer and telegraph and telephone sets, which, in perfectly dry ground and in a dry season, functioned poorly or not at all with ordinary grounds. Right then he began experiments with a view to seeing what possibilities, if any, the tree had as an aerial. But in 1904 radiotelegraphy was far more undeveloped than at present, and vacuum amplifying tubes were not thought of.
UNQUOTE