On 3/2/2011 8:40 AM, Wimpie wrote:
On 2 mar, 13:58, "J.B. wrote:
On 02/23/2011 10:00 AM, RadioWaves wrote: Today I have put my homepage online with information about the Magnetic Loop
Antenna.
http://www.qsl.net/pa7nr/
PA7NR
Hmmm. A "magnetic" loop antenna. Must be some other types of loop
antennas as well. Maybe there are also "electric" loop antennas.
Guess they left something out of all those antenna textbooks I have ;-)
Sincerely, and 73s from N4GGO,
--
J. B. Wood e-mail:
Hello John,
When you cut the loop at two opposite positions, yes, you can make
your "electric" loop.
It will generate lots of E-field, you may need another coil for
matching, and it is probably less efficient then a short straight
dipole with massive capacitive disks to get larger I*delta(le)
product.
Best regards,
Wim
PA3DJS
www.tetech.nl
In case of PM, please remove abc first.
Hello, and the not-so-subtle point is that there aren't magnetic,
electric, or any other such "types" of loop antennas. There are just
loop antennas that can further be described as shielded/unshielded,
balanced/unbalanced, electrically small or large. Just like we don't
transmit (propagate) electric (E) or magnetic (H) fields by themselves.
The purpose of an antenna is to radiate and/or intercept an
electromagnetic field. By definition energy radiated by a transmitting
antenna is not temporarily stored in the antenna's local electric or
magnetic field. It's been released into free space subject to
interception by a receiving antenna(s) or any other parasitic
structures. The receiving antenna transfers part the intercepted energy
to the load (receiver and other dissipative losses) and scatters the
rest back into free space.
By contrast, a transformer, for example, is a "magnetic" device that is
intended to transfer energy by a localized means (induction) other than
the propagation/interception of electromagnetic radiation.
To further confuse the issue, a conductor in the near (reactive) field
of a transmitting antenna will have current induced in it by the
antenna's local electric and/or magnetic fields. However, that's not
the usual purpose for which we design antennas. An exception might be
the immoboliser (PATS) system used in late-model motor vehicles that
incorporates a ring antenna embedded in the steering column that is
closely coupled at RF frequencies to the transponder chip and loop
antenna embedded in the vehicle ignition key. So is it a
transmit-receive antenna configuration or a primary coil-secondary coil
transformer configuration? Given the proximity of the inserted key to
the steering column I would guess the latter. Sincerely,
--
J. B. Wood e-mail: