False signal on steel

[Birdseed]

Just curious, I went out to an old abandoned railway station to try my luck. Found a few old shotgun cartridge ends and some old power meter company lead seals, but mostly the area was so trashy I could not make much sense of the ground. Also a hot autumn day in Tasmania made digging in rock hard ground unpleasant.
Well I was about to give up when I got a big signal. High pitch like a shallow copper coin or brass ring, loud enough to be uncomfortable in the 'phones. I took out a plug and tested for content, but nothing. A quick sweep confirmed the target was still in the ground. Still a nice high pitch. Pro-pointer confirmed it was not far down and in the centre of my hole. Well to cut to the chase, it turned out to be a 4 1/2" square 1/4" thick, very rusty steel plate with an inch diameter hole in the centre. Typical of finds around railway yards etc. My question is why the nice high pitched signal, target was under centre of search coil both in disc and pinpoint. I removed the target and checked the area again, no other targets within a yard of the hole. Ground was old fill, mostly clay and crushed rock with about 4 inches of poor soil on top. The Sov GT does not often get fooled, and I can usually sort it out when it does, but this time we were both taken in. Has anyone else had similar experiences? Maybe it was the size of the target. It did not appear to have been galvanised or zinc plated, but maybe it had been and the residue was still in the soil. After I took it out of the ground the Sov GT recognised it as iron, nulling and returning with the standard deep growl.
Any comments appreciated.

Pete down-under

 

[GunnarMN]

pet this is common on large flat iron , it also may have been deredting the ground signal as well the only thing is as you past slow the sweep and see if it gets a bit scratchy as it passes the object, you know me i dig Iron all the time seems like the bigger thicker and flater it is the more it sounds like a good target in disq should give a low in fixed all metal this would be a clue its not a high conductor I would keep seaching that spot and start with the strongest signals then keep going down the line i bet some gold comes out from the ground

 

[bootyhoundpa]

not all iron can be eliminated no matter how hard we try....horse shoes.flat plate steel,even some nails will sound good....ive dug plenty of deep iron that sounded high tone especially if the ground is moist....you could lower your sensetivity a little or some times iron mask off actually discs out iron better than iron mask on -go figure...

 

[Tin Fin]

I've been having this happen - today, found a 6" bolt that sounded that way. I'm starting to turn the sensitivity down if I suspect iron; sometimes that tells me it's iron, sometimes not. Being still new to the Sovereign, I'm glad to find out from others that this is not abnormal. I'm finding similar sequences to the old galvenized Mason Jar lids at old house sites. The other iron item I found today because of the same signal, I still haven't figured out what it is. About an inch thick, and 3x4 or so inches wide and long. Heavy cuss it is too. Haven't weighed it yet, but will. It could be some scrap from the RR near by, not sure. Good question though.