4 1/2" X 7" vs. 5" vs. sensitivity

[jjwest]

This is sorta of a 2 into 1 posting. I have a 5" coil but rarely use because of it's small ground coveraged. The 8" coil is the one I've learned to live with even in trashy sights and the 10 1/2" for open low trash areas. A 4 1/2"x7" coil was acquired and used last week in the desert and a local park. It's coverage was obviously better than than the 5", but it's depth was the same(3 1/2" to 4"). What the heck is going on. This is contrary to what Mike(Virginis Beach) said.

I then reread his posting about the 4 1/2x7 and read that he was using manual sensitivity. A quick air test in the kitchen with different coins showed that both coils are about equal(3 1/2"x4" in depth) using AUTO sens which I have always used. Switching to MANUAL sens and running a series of air test with MANUAL sens(20,18,16,14,12,10) showed and increase of 2 to 3 times air detection distance versus AUTO sens. The 4 1/2"x7" coil gave about 1/4" to 7/8" more air detection distance than the 5". What I have read is that air testing is not the way to test.

So have I missed a lot of things in the ground by using AUTO sens. Andy Sabisch's book says that a "slight loss of detection depth will occur in AUTO sens but the detector will be more stable". A slight loss doesn't like much but if some revelance can be given to air testing and the detection distance increases 2 to 3 times in MANUAL sens, then MANUAL sens needs to be looked at more closely.

 

[Mike (Virginia Beach)]

In my experience, Semi-Auto sensitivity loses HUGE depth. I never use it. As for air tests, they are worth SPIT. And you can change that second letter in the word SPIT if you like.

I can run my 4.5 x 7 at sens 32 manual in most spots and have it be fully stable. Near power lines I have to drop to maybe 30. And at those settings, it gets depth equal to or close to the stock coil. So my theory is it's your settings that are responsible for your lackluster results.

I'm pretty sure that any posts I made on the coil clearly stated the fact that I was cranking up the sensitivity...that's one of the best things about that coil.

 

[jjwest]

What I am trying to find out is from others previous experience if there is really that big of difference in detection depth between AUTO and MANUAL sens.

Are you using a Quattro for your 32 sens setting? The highest I've seen available is 20.

When testing the 4 1/2"x7" last week and the detection depth was just 4" in AUTO, I was still able to find buttons and bullets in the desert and coins in the local park. I know the detection depth was 4" because I would lose the target if I lifted the coil about 2" above the ground to improve pinpointing. I would have to put the coil back close to the ground to find the target again. The target was dug out at about 4" depth. This 4" in the ground depth is very close to what was seen in air testing. This is what caused me to see if any credit could be given to air testing.

 

[Mike (Virginia Beach)]

OK, I assumed that you had read my post on the Explorer forum. Actually, I was talking Explorer SE. Which the Quattro can use the same coils and vice versa. And on the SE, 32 is MAX. So I would think on the Quattro (which I used to own) you should be able to run the 4.5 x 7 at 18 to 20, depending on the area you're in. And yes, you will lose a LOT of depth in Auto. FORGET auto. Run your Quattro as hot as you can in a particular area. Here in my area, I can run the Quattro at 18 in the wet sand at the beach and 17 in the water. At most land sites I could do 17 or 18. In iron-rich areas, maybe 16 or 17. But you will probably get better depth at 12 to 15 in manual than in auto at most places.

 

[jjwest]

Thanks for the feedback on the levels that you run in MANUAL sens. I'm now anxious to go back to some quality sites that I thought were played out. Manual sens here we come.

 

[Golden]

Hi iiwest, I pretty much use the same settings as Mike in mineralised and iron infested ground. I NEVER use auto in relic hunting on the goldfields, you lose depth, targets, the finer points of detecting. On the goldfields, I run High Trash, jack the sensitivity as high as I can, but if I feel that I'm losing targets, I'm not afraid to bring it down to 12 or 14. You'd be surprised at what depth you can still get with these settings. But yeh, compensate for the area between the coil and ground, to get a true depth of target reading. Also bear in mind that larger targets will often read deeper than the scale shows. I personally haven't tried the other coils you mentioned, I just use the 7.5 inch on the goldfields, the 10.5 inch on the beach. And I don't lower the sensitivity from dry sand to wet sand or going into the water. I don't find a need. Just noise cancel if need be, between the changes on the beach, if your detector goes a little crazy.
Golden