At 12:49 1/04/2003 +0100, G3KEV wrote:
Its a question of requirements.
1. These Decca coils were used only on TX and 10/15 db loss was acceptable
by putting these coils in a metal cage for environmental reasons.
10 to 15dB coil loss means 90% to 97% of all power lost (= transformed to
heat) in the coil.
I wonder why the Decca guys went through all the trouble to built large
antennas with an acceptable efficiency and then decided to use 90 to 97% of
the power just to heat the loadingcoil ?
This apart from the fact that dissipating more than 90% of the Decca power
in a coil would probably melt it.
2. Heated coils generate noise, in fact the coils should be kept cold, but
again in a TX only mode it does not matter.
I doubt that the few nV noise generated by a warm coil (or resistor) are
significant. Atmospheric and manmade noise will be many 10dB's stronger.
The above info is old hat for those in the know, it would appear some have
led sheltered lives in the wireless world.
Aha ... that might be my problem !
73, Rik ON7YD
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