antenna-theory.com

[franzellin]

following the Monopole antenna page, it is written that this one must be in contact with a PEC (perfect electric conductor)

For this reason I understand that some of these antennas have a magnetic foot to stay on a metallic surface

I also understand that the electricity flow is fundamental in the antenna theory

The most monopole antennas are either for DBT (tv) or WIFI in both cases they are connected to a Receiver or a PC that are insulated from the ground with 4 rubber feet or in a car with 4 rubber wheels

1) If the antenna is not on a Metallic surface grounded, but for instance fixed with a biadhesive scotch on a wooden surface or glasurface , it means insulated from the ground, how does the antenna work?

thanks for the explanation- renato

[R. Fry]

Monopoles will function rather well by driving them against another conductor, even if it is not "perfect." For equipment in the UHF bands and above such as DTV and WiFi, that conductor can be provided quite effectively by the chassis "ground" or common path for the circuits of the device.

[franzellin]

ok, it means that the "ground" has not to be perfect , sometimes I notice that touching the antenna with the fingers, gives a better signal, I suppose is due to the better grounding.

Would it be theoretically positiv to connect the monopole with a better ground or the difference is not relevant?

thanks - renato

[R. Fry]

A device that includes a monopole antenna likely has optimized its performance when used on that device. Adding conductors to it might reduce performance. For example a conductor connecting the circuit ground to a ground rod can change the feedpoint Z of the monopole to the point where little (or less) r-f power is radiated or received.

[franzellin]

understood, thanks

[gilroy]

The current distribution must be zero at the ends of the patch; current can't flow "off" the patch. The voltage is out of phase with the current. You have to think about how the current might flow to produce radiation; this takes thought and creativity. You need to think how the various "modes" or how the current will flow at each frequency; the current distribution will be different at different frequencies.



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