Recent content by davidhills

Good Morning can anyone help explain what this statement really means, when referring to a npn transistor in common mode, as an amplifier. "The collector is a high impedance when compared to the emitter" what's the pratical implication of this statement thanks David

Good Morning What is the Physics of the transfer mechanism between the energy in the antenna and the propagated wave? thanks David

Thanks Bob Does that mean that if you had a theoretically perfect antenna system with only Capacitance and Inductance you could not extract a signal from it?. Or propagate one? If you need some Real resistive component, how to you design it in? David

Afternoon Can any shed any insite of on the faulty logic The propagated Magnetic field and Electric field are orthogonal and in Phase. The magnetic field is associated with the current and the electric field with the voltage Yet the voltage and current in the ¼ wavelength monopole...

Afternoon I think I may be able to answer this myself now. Physically it's a monopole but electrically it a dipole. The half that missing is the ground reference plane. So a monopole whip antenna has a sort of reflection with the ground plane making a dipole...

Many Thanks Born2bwire That's helped a great deal. A quick thought, if a 1/4 wavelength monopole antenna was resonating at its natural frequency (say a one meter antenna receiving a 4meter signal) since the resonate pattern is not symmetrical how do you know what end of the monopole to...

Morning by monopole crystal radio , I just ment a cyrstal radio set with a long single wire as the antenna, using the ground/earth as the second pole. I am very restricted as to where I can put the antenna up, and am trying to work out some optimisation before felling any tree's ...

thanks for your reply Does this mean that on a receiving antenna the length of the antenna is proportional to the energy absorbed (intuitively I can see why it may be proportional to the energy that could be absorbed, the area has doubled that the radiation is striking , like doubling the...

Good Morning Can anyone help me understand why, apparently the physical length of a monopole end feed wire for a crystal set need to be ½ the wave length of the desired signal. The reason I ask is, that I understood that, if you have a variable coil in series with the antenna, the...