rabbit ears antenna (why)

i want to ask about rabbit ears antenna what is the effect of changing the angles between the two dipoel the picture become better or worst what is the effect of angles here as well when u incease or dicrese the lenght wht does it effect this is in simple case
what about if we put amplifiers and concet to voltage

i know that it will better but what are the reasons according to antenna theory
thanks

check these
h**p://www.angelfire.com/mb/amandx/dipole.html
h**p://en.wikipedia.org/wiki/Dipole_antenna
hope they are helpful

I assume you are talking about TV reception?

You can make the antenna longer or shorter, and therefore "tune" it to the channel's frequency. If you are receiving channel 3, you want the length as long as possible, if you are looking at channel 13, you want the length shorter.

By changing the angles of the receive antenna, you are changing its polarization. The TV signal's polarization rotates as it bounces off of things (buildings, the ground, etc), and you want to match the receive antenna polarization to the TV signals.

you have asked for detailed theoretical answers and not practical

dear pakitos thanks for ur interst in my question but as u said i need theoretical answers but atlest i got a simple answer i hope to get it ... maybe you say read the books but really somtimes people have answers better than books .. any way thanks for every one

Rabbit Ears are just a simple adjustable Dipole. As said above adjusting the lenght of each leg will make the antenna resonant on different frequencies. Ajusting the angle between the two "ears" will affect the radiation pattern. Making a smaller angle the antenna will be behaving more like an isotropic radiator i.e. receive signals all around with almost no attenuation. If you instead increase the angle, the pattern will become that of a straight dipole, having deep nulls at each end. This can be very handy when trying to remove unwanted signals (ghosting reflexes).

Finally the feeding impedance will decrease when decreasing the angle, but as assuming it is for receiving purposes only it will have minor implications.

/WD
"My Name Is Earl S3 E20 Randy:Do you want to adopt an ear-less rabbit?" 8O
:D