Searchcoils and Gain

[Wirechief]

Do any searchcoils exhibit any kind of gain in signal for either transmit or receive? I'm comparing the search coil to a high frequency isotropic vertical, like we use in ham radio. Thanks. Wirechief.

 

[Prospector Al]

That's wishful thinking O chief! The most efficient coil for both transmitting and receiving is a circular one...

There's a trade-off between its reach and sensitivity to small targets.

Prospector Al, NB6K

 

[Wirechief]

Hey Al! Thanks for the response and I just had to ask but I didn't think there would be. Great to meet a fellow ham here on the forum. I haven't been active in the last 6 months. I'm too caught up in the metal detecting hobby now. Your call seems familiar and I am KA5QYR. I'm a Ten Tec fan and enjoy cw and building QRP rigs. Ok Al maybe I will run into you sometime on the air. 73 my friend and God Bless ya! Wirechief. I'll cu agn.

 

[Eric Foster]

Hi Wirechief,

Better to look upon a search coil as a transformer winding, that is loosely coupled to the target. The more turns and inductance the winding has, the more signal is coupled into and out of the target. Inductance goes up as T squared, and so does the signal, but the inductance is constrained by the width of the TX pulse, and also by the time it takes to remove the energy at the end of the pulse. If you make a coil with separated TX and RX windings, you can optimise both and get considerably more range, than with a single winding for TX/RX.

Eric.

 

[Wirechief]

Hello Eric and thank you for the input and definitely more material for my PI notebook. Always appreciate your help. When making a searchcoil is there a specific window that a person wants to keep the Q of the coil at? Thanks Eric for your time also. Wirechief.