Maryland Free-State Treasure Club

Detecting in Hot Dry Soil

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Deep targets on warm days are harder to find because the ground emits warmth, competing with frequencies of the search coil. Since heat, radio waves and light are all electromagnet wavelengths of varying degrees, the warmth of the ground tends to interfere with, or absorb some of the electromagnetic frequencies the search coil is emitting.

It isn't so bad when the soil is still moist from rain and the eddy currents responding to the search coil are still pretty healthy.

In the normally dry months of July and August the soil is dry, powdery and hard to dig. The ground can act as a mirror to the frequencies emitting from the search coil, except when detecting large targets, cans, screw caps, etc.

The search coil signals are competing with heat waves, the eddy currents are weak and parched and the ground is unyielding and almost impossible to penetrate with a digging tool.

Under these conditions, plugs would be very difficult to manage even if you could dig down a few inches. The soil simply falls apart. Even the best repaired plugs turn yellow as the connecting root system is disturbed, cutting off water and nutrients from surrounding roots.

HERE'S HOW WE LEARNED about the fruitlessness of metal detecting in hot dry soil:

Years ago we buried a variety of silver coins about six-inches deep, as a test field, on an outing at a local park. The day was hot and the soil was dry. Nobody could detect them. We dug them up and re-buried at about four-inches. Only one member could detect one of the larger coins. At two inches the signal from the coins was stronger, but the dimes gave a weak signal.

If the soil had been moist, the coins would have screamed at us at six-inches.

Detecting for relics in the woods is preferable to open field detecting in dry conditions because foliage of trees and shrubs can keep the soil shaded, cooler and damp.