Which book is best for learning about concepts like
antenna,reflection,swr, etc. I am working only at hf band. If there is
any online tutorial ?
Try these links:
http://en.wikipedia.org/wiki/Smith_chart
http://en.wikipedia.org/wiki/Reflection_coefficient
Don't feel too bad if this subject is not too clear. It used to be
introduced in about the fourth semester of Electrical Engineering, usually
in Complex Circuit Analysis.
Here's the $2 version:
Impedance is a complex quantity (i.e. it has both Phase and Magnitude.) The
reflection coefficient is a measure of how well a load is matched to its
source impedance; the match determines how much power is reflected by the
load. Whatever is not reflected, is absorbed by the load. In the case of
an antenna, the "load" is free space; therefore all power absorbed by the
load is radiated into free space. We would like the reflection coefficient
to be 0; when that happens we have a perfect match and all power is
radiated.
Like impedance, the reflection coefficient has both a phase and a magnitude.
When most people talk about the reflection coefficient, they only conside
the magnitude and not the phase.
"Cecil Moore" wrote in message
...
palaniappan chellappan wrote:
Thanks for replies, but i couln't able to conclude anything from the
two complementary replies i got :-(.
If the voltage and current are in phase at every point up
and down a transmission line (with a resistive Z0), there
are no reflections. If there are reflections, the voltage
and current are in phase only every 1/4 wavelength.
Which book is best for learning about concepts like
antenna,reflection,swr, etc. I am working only at hf band. If there is
any online tutorial ?
Unfortunately, only the older (pre 1990's) ARRL Antenna
Books present a decent explanation of reflections. The ARRL
has stopped discussing forward and reflected waves and
started discussing impedance matching. IMO, it's part of
the dumbing down of the ARS along with the rest of the US.
Walter Maxwell literally wrote the book on "Reflections". His
web page is: http://www.w2du.com Worldradio magazine is on
the verge of publishing "Reflections III". Their web page
is: http://www.wr6wr.com
You might get something useful from my Worldradio magazine
article available at: http://www.qsl.net/w5dxp/energy.htm
--
73, Cecil http://www.qsl.net/w5dxp