LC Resonance Signal Origin Detector

[flippineck]

Would I be able to conveniently use a small coil of wire (with or without a ferrite etc. core) in parrallel with a capacitor to detect the strength of a radio transmission at a particular frequency, from a particular direction, if I had some kind of shielding behind it?

I was thinking of arranging say, four inductor coils on a pcb each with it's axis at 90 degrees to the others, with a 'reflector' of some kind in the middle

And, then parrallelling each coil up with a suitable capacitor to achieve a resonant frequency at the target value.

Then I could use some device to sample the AC voltage apparrent across each of the four capacitors, in order to determine which was the highest out of the four.

The highest of the four values would indicate which of the inductors was pointed at the strongest signal source?

If the pcb were laid horizontal I could determine which of North, South, East, West sent me the strongest signal?

I'm thinking around a 'where on the compass is the transmitter?' type device. Specifically I'm thinking of UK 4G frequencies i.e. 1800MHz and 800Mhz

 

[hevans1944]

Your idea is sound in theory, but IMO totally impractical at these two frequencies.

 

[flippineck]

I feared as much :-(

reciprocal of (6.2831 * root LC) with L in henries and C in farads would give me the resonant frequency in hertz if I wanted to play around with values?

Is there an easy way to calculate the inductance value of a simple air cored inductor (e.g. copper wire wound round a pencil)?

Does this look valid .. http://www.66pacific.com/calculators/coil_calc.aspx - ?

If so I make the resonant frequency about 863 MHz with a 10 turn coil 5mm diameter, 5mm long and a 0.01 microfarad capacitor?

Is my maths ok there

 

[hevans1944]

Try solving the equation using scientific notation for the variables. The coil dimensions and capacitor you specified resonate at about 2.73 MHz, assuming coil inductance is about 0.339 μHy with 0.01 μFd capacitor.