Hi Chavdar,
?
What bothers me in your published article signals-mag_loop_engl.htm where using known equations you concluded in the? short current mode the induced current in the loop is independant from frequency, using the proposed equivalent model of SML:
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?I = w x S x u / c x L , where w - number of loop turns, S - square area of loop, u - magnetic constant, c -velocity of light and L - loop inductance.
?
Also, this postulate does not suit with your "dummy" aerial model? with a parallel LCR circuit across amplifier input? because it is frequency dependant.
Let's for a sake of argument? forget about the mathematical description of small loop antenna behaviour.
We have a metallic loop where a magnetical filed induces current and that loop has distributed ohmic resistance and inductance. Across loop terminal points we connect a 3 ohms resistive load ( for short current mode ) to close this loop. Only when the reactive element? in series, namely the inductance, is significantly less than the ohmic resistance of the loop I suppose we can say we have a flat independant frequency response of antenna.
The frequency rises so the reactive resistance of loop antenna and the current through the load diminishes.
Now let's go back to test circuit ( dummy aerial layout ) proposed by you:
1. Where is there the current Norton's source ?
2. For lower frequencies the parallel circuit shall? shunt away more current from the 3 ohms load than for higher frequencies ( less applied signal to the amplifier ).
? ? In reality the AF for SMA is greater at lower frequencies than at higher frequencies ( more signal is applied to the amplifier ).
Your detailed response is appreciated.
?
Regards,
?
Raphael
?
?
?
?
