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Getting a Handle on the HF Coil....13,333Hz Hunt
Posted by: CZconnoisseur
Date: October 18, 2017 03:01PM
Mike and I got out the other night to one of our usual haunts that still coughs up 100-year-old plus coins most of the time...after last hunt using the 9" HF coil in 28.8kHz, I felt that a lower frequency would help me dig not as many foil balls this time around. Well, in short, it was sucessful - still dug plenty of foil and other aluminum bits as well as some iron, but this frequency was still very sensitive to more solid pieces of metal at depth.

The only two deep coins were the 1912 D Wheat and 1948 nickel which were several feet apart at the 7" level. Both coins had iron and/or aluminum within 3 inches of them, and I remember the nickel having a rather large pinpoint "signature". Anything that is "bigger" in the audio and sketchy at the same time - I really want to dig these out!

A couple of deep iron blobs hit a little harder in 13K, and I didn't check these with 28K to see what differences may or may not have been present. An unusal find was the graphite or maybe ferrite rod that was next to a large rusted ball bearing.
Out of the hole, this weird rod thing IDed at 27 in 13K, and 28 in 28K...not much VDI spread on that item - a little strange indeed. The rod was 10" deep and a faint, but clear signal.

The .22 caliber round was 9" deep and quite a surprise from that depth. From the same depth was a lead finial...solid non-ferrous, non aluminum items have smooth edges and hit very deep with this coil. I had Sensitivity on 90 and it ran very quiet indeed. The pencil eraser ferrules hit hard with this coil, and even worse are deep ring pulls with or without the beavertail. I don't mind digging lots of junk for a couple old coins - in fact it's come to be status quo whenever I manage to get out!!! :buds:

It seems that the round and flat foil pieces hit the hardest out of all the foil shapes and configurations, no surprise there...13K didn't want to assign VDI to most of the foil, whereas 28K tried harder to assign a number value. Switching back and forth helped me pass up a few foil bits, I dug several just to prove it....

There is significant VDI spread between 13K and 28K programs, and no ID norm, so one has to learn those values. For example, a shallow nickel will in 13333Hz will give a VDI of 56 but in 28829Hz VDI will be 72. Clad quarter in 13K is a VDI of 93, in 28829Hz it's 96-97. Earlier I stated the there wasn't much "up-averaging" with deeper fringe targets, but that is mostly NOT THE CASE! Maybe our soil has something to do with it, but it's just something to live with...

One thing that sticks out is that shallow coins no matter what type up to 6" deep hit very hard vs smaller items. Switching between 13K and 28K on coins give a good VDI shift but also the audio remains "large" - it's hard to describe but after a few hours it makes sense....

The 9" round HF coil is *almost* like a completely different detector than its LF counterparts (my opinion), and so far it seems to be a better overall coil that's more adjustable for a broader range of detecting. It's definitely quicker, even at Reactivity 1 on the lowest Hz setting (13333Hz). It doesn't like straight pieces of iron as much, but bent or blobby chunks will throw it off at depth. 28kHz is very sparky, and will hit some of the smallest little pieces of aluminum (read GOLD in a rural, remote setting). I would imagine a wet or dry beach setting would also be tailorable with the 54kHz band. Also, the freq offsets are superb - this is just icing on the cake for some folks, but the geek in me loves the potential!

Re: Getting a Handle on the HF Coil....13,333Hz Hunt
Posted by: NiagracountyNY
Date: October 19, 2017 05:23PM
Really appreciate the info!..Ive been considering one of the HF coils myself. Sounds like it would be worth trying..Keep us informed on your thoughts as you use it more ..Thanks ..HH

Re: Getting a Handle on the HF Coil....13,333Hz Hunt
Posted by: calabash digger
Date: October 25, 2017 05:25AM
nice hunt, and thanks for the info .I'm using my round coil all the time now.

Re: Getting a Handle on the HF Coil....13,333Hz Hunt
Posted by: Tony (Michigan)
Date: October 25, 2017 06:44AM
Those pencil erasers and .22 shells sure sound nice, don't they? :-)

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