Monday, Nov 01, 2010 at 20:02
Hi ob,
It will still affect the performance, whether the second
antenna is transmitting or not. Some of the transmitted signal will be absorbed into the adjoining receiver.
Basically, an
antenna design, in part, depends on its surroundings. Add metallic bits close around it that weren't part of the design and they affect the performance, especially if the offending bit is around 1/4 wavelength or multiples of that. But any length, mounted close to the working
antenna will affect it. And it will cause some transmitted power to be reflected back into the transmitter (usually with no damage). You may be able to tune out the affected VSWR (reflection), but the radiation pattern will still be affected.
This is used to good effect on yagi antennas (eg, TV antennas) where a slightly larger than 1/2 wavelength rod placed 1/4 wavelength behind the dipole (
antenna) causes the signal to be reflected almost completely; ie no signal behind the reflecting rod. Similarly, slightly shorter rods placed in front of the dipole will enhance the signal, but narrow down the beam width and improve the gain. This is all part of careful design, otherwise you don't get the desired effect.
But conducting elements of random length and random spacing placed nearby will cause all sorts of unpredictable radiation patterns.
Hope this helps.
Here endeth the lesson....
Gerry
FollowupID:
705903