Calltrex wrote:

Yeah the folded dipole that is. We see there 4 x ¼ = 2 lambda.
Following the antennabook one can earth the middle of that folded dipole.
And feed it with a coax.
So from there we can bridge the mantle from the coax to the middle of
the straight
dipole piece. See it ? Now my problem in visualising that; the current
from hot goes
to the ½ wave dipole....hits ground there.....appears out of the
ground(!).... hits the
second ½ wave....and dives back in the coax mantle. If this is true i
can't imagine it !

Now the violin string. Take one string attached between two walls or
whatever.
Exite it. Now ground the string in the middle.....exite the first
half......and the second
halve will vibrate also ?? Thru ground ??

Are the two statements right? The mind boggles.

It's even cooler than that. You can put two antennas miles apart with
nothing but space between. Put current through one, and current will
appear in the other -- THROUGH SPACE!

Put two violins close together and pluck the string of one. The
corresponding string of the other will vibrate. THROUGH AIR!

You mind has just begun to boggle.

Roy Lewallen, W7EL

Roy Lewallen wrote in
treetonline:

Put two violins close together and pluck the string of one. The
corresponding string of the other will vibrate. THROUGH AIR!

Then consider the (say) three strings of a piano note, and that if their
resonant frequencies are close enough, they vibrate in phase (that implies
at the same frequency of course), well they do until the amplitude of
vibration dies down sufficiently and they 'unlock' and vibrate
independently.

You mind has just begun to boggle.

Now, somehow I can see this being used to explain an antenna.

I hear the behaviour of a string in a violin being used to explain why
resonant antennas are just better, and how they "fairly suck the power out
of the transmitter, like a string sucks the power out of the bow".

Owen