The etracs standard double 'D' coil is real the best all round coil for the job treasure hunting.
The Double "d" puts down a narrow blade like field the near full width of the coil that means you don't have to over lap your sweeps much. Plus it helps heaps to reject mineral interference IE salt in beaches. That fact of the matter is Aust history is 200 years so most relics coins are rarely deeper than 300mm except where earth and sand is moved. Beach etc I find coins easy 400 mm down clear as a bell.use Expert_ DEEP mode. Deep mode will amplify faint signals automatically.
Larger mono coil means you will go deeper but you wont cover more ground !!! The mono coil emits a cone shape so the edges of the coil area aren't detecting deep so you want a full deep search you will need to over lap each sweep by half the coil width.
A smaller mono coil will assist in rubbishy areas as there will be less targets to identify and shallower at the one time. But if you learn to slow sweep across rubbishy areas with fast recovery on and trash density high you can learn to use existing coil.
Another advanced skill and fantastic feature on Etrac is in
over the rubbishy ground until it locks on to the target signal you want......... IE Gold or coin 12:24 what ever. Once locked slowly target etrac in the normal manor.
Note when you step 90 degrees around the target it might vanish due to other rubbish masking it, Try another angle to refind it and form an X to dig as per normal.
OR
Pro Tip:
Finding surface targets: Even over
steel re-enforced concrete. This no book taught me, probably for good reason but it works.
" Deep mode will amplify faint signals turn it off. Always have deep on" Exception In rubbishy areas and you are looking for a surface target DEEP off. Set "Fast recover", "high trash" Set sensitivity to manual. while detecting reduce the manual sensitivity to about 6. if you still are picking up deeper rubbish/steel lift the coil 100mm above the ground place a coin on the ground so you know only a ground target is in range/detected. OK off you go find your surface target excluding 90% deeper rubbish.
OR For beginners a
surface target with NO other metal around will beep
three times on the etrac. Bepp Beep Bepp.
Firsts Bepp is leading edge of coil (note incorrect reading will display here)
Middle beep is main coil field (correct reading
third beep is tailing coil edge leaving target . Note if you hit a surface target with the outer edge the wrong id will show only centre field will be correct.
So Three beeps matching sweep speed will mean surface target to IE 50mm down approx.
If you have two surface targets under coil you will get 6 beeps, 3 targets 9 beeps.
EG two surface targets will give you 6 beeps a deeper target will also give you a single normal beep so you will have 7 beeps all up. lol
"tip step 90 degrees to target area this may eliminate separate pieces of rubbish from coil path making life easier and reducing confusing beeps signals. This really screwed me up when i was learning till i dug all targets and worked it out.