Martin… yes DJ makes a special point of mentioning the feedback across the country about dry soils generally decreasing VLF detection depth. But then too, there are exceptions to the rule.
Some soils become more reactive as soil moisture increases. This phenomenon can reduce EMF penetration and play havoc with target ID. Some experts attribute this condition to enhanced soil mineral (non-conductive iron) ionization that results directly from increased soil moisture. Let’s look at a documented Alabama ‘red’ soil sample lab report from one of our leading detector manufacturers.
The lab report describes the soil in a dry state as “bad ground” but well within the ground rejection range of their current detector models. It recommends that soil type should only be searched when in a dry state. Below is a direct quote from the report about that same red soil in a wet state.
“When wet the sample becomes very had ground, difficult to reject and or penetrate. This type of iron oxide, because of its consistency, achieves a solidity or connection between iron particles making it much harder to reject when wet.”
Terry… it sounds like Dave doesn’t have a satisfactory explanation, although he seems to feel that there is something to it over predominately non-conductive soils. In my ground dry to compactive soil moisture content gives the best detection depth. When wet, those deeper targets in my test plot are harder to acquire. How much that has to do with our semi-annual fertilizing is an open question. Quote from DJ below…
"Most reports of improved depth after a good rain come from wetter climates. I used to attribute this to easier digging, not to any electrical phenomenon, since soils of wetter climates usually have moderate to low conductivity whether wet or dry. However, the great drought of 2011 changed my mind. Just too many reports from detectorists from Texas to the Atlantic who have planted test gardens, and they noticed that the drier things got, the weaker the target signals got, and when it finally rained a good one the signals came back. Digging didn’t have anything to do with it. So, now I believe the effect is real. I’m aware of several theories which attempt to explain it, and I don’t like any of ‘em. So for now I just accept that it really does happen and I don’t know why."
Now as to salt / alkali question, I don’t hunt such ground, never been at a seashore either, so anything I might say would be talking through my hat. No direct experience. While I think most of us know what the general suggestions are… it would be nice if a few of the guys here who do hunt such areas would comment.
I know you’ve got a copy of Jim’s “Advanced Prospecting & Detecting for Hardrock Gold”. He discusses the wherefores in considerable detail starting on pp.19 and 20… then again on pp.25 and 26, and more extensively on pp.31 to 36 with a few suggestions included to deal with those conditions when wet. It sure makes for an interesting read.
There’s no question you’ve hit on the key point Terry. Dave has referred to widespread information to suggest that some amount of rainfall (excepting alkali areas) does improve detection depth. Of course it’s a given there will always be anomalies / exceptions as described in the first example above.
Jim.
