The intention of the following:
1) ALL TRANSMISSION LINE(s): Fields close onto themselves. The system is
self contained as far as the fields are concerned.
2) ANTENNA(s): Fields open onto space (hopefully free space). The system
is open and not self contained regarding generated fields.
Dave - W?LEV
On Mon, Aug 17, 2020 at 1:48 AM Jerry Gaffke via groups.io <jgaffke=
[email protected]> wrote:
Roger and Jim.
I looked at Roger's png first, and that does explain why a dipole radiates
and a transmission line does not.
Will dig into Jim's antenna book when I have a chance.
Many thanks for the quick answers to a complicated question.
Jim wrote:
You would have problems in other senses, some of which manifest in what
you might call efficiency.
The radiation resistance gets very low, so the current, for a given
radiated power, gets very high.
So, for a "real antenna" that has ohmic loss, that becomes a big
fraction of the "power at the terminals"
A transmission line with an open at the end has zero current and maximum
voltage there.
A very short dipole would be a minor step away from that case,
Seems the impedance into such a short dipole should be very high and the
antenna current thus very low.
Though Jim used the phrase "for a given radiated power", which complicates
things some.
Guess I better read that book.
Jerry, KE7ER
--
*Dave - W?LEV*
*Just Let Darwin Work*
