GPX - DD coils -Cancel Mode & power lines

I was reading in another topic (Which coil for small gold in ironstone) and it started me thinking about an area that I would like to work under some power lines. I usually use a small mono on my 4000 but can't get close to the power lines because of the interfeance. I was wondering if changing to a DD (the standard 11") would do the trick or if I need to goto Cancel mode and a DD. I think I read JP said Cancel mode only works on DD. Once I accidently bumped the switch from mono to cancel, it took half an hour to notice, boy it was quite. I then did some tests and found that the mono in cancel mode wouldn't pick up anything that was not touching the coil and large, ie very very poor response. Anyone got any tips please. Cheers Mark.

An 11" Salt Coil will do the trick.


Driller.

Hi Mark
, with the 4000 under power lines try ,, turn your boost & gain up,, run in cancel, deep mode, normal timings, fixed tracking & motion slow,, i use the standard 11'' dd coil

cheers spider

Thanks Spidertice I will give it a go. Hi Driller, I don't want to spend the money on a maybe, I'll see how I go with the DD first. Cheers Mark.

Depending on how far you are from the interference you can back right off on the Stabilizer control using a small Mono and then make adjustments to the Motion and Gain settings even try using the Quite Audio filter, but if all else fails then a DD coil in Cancel mode or a Nugget Finder XP coil in XP mode in conjunction with Mono mode or a dedicated out of phase DD in Mono mode will do the trick or lastly a figure 8 or AI coil. Phew!!!!

Because Cancel mode and the Mono/XP modes behave similar to a Mono coil (sensitivity wise) you can use the Enhance timings to try and tame ground response.

Regards

Jonathan

Thanks JP for the very good helpful info. as always.

Four ways to combat interference and power lines:

1) Dedicated Anti-Interference(or Salt) coil (figure 8 coil).
2) NF XP coil. In XP mode and Mono mode.
3) Dedicated Out of Phase coil in Mono mode.
4) DD coil in Cancel mode.

If all 4 coils above were the exact same size. Which method(s) would go the deepest I wonder?

You will find that you will lose sensitivity and depth on all those settings and sometimes not totally cancel out the inteference. An 11" or 14" Coiltek anti-interference (Salty) coil is the only way to do the job properly. The cost of either is only a few grams of gold.

Cheers, Jim

Thanks Jim, besides 11" and 14", CoilTek A.I. coils also available in 17x11", 18", 24", and 27x21" sizes.

http://www.coiltekmanufacturing.com.au/faq.html#q12

12. What are the benefits in using an Anti-Interference coil?
An anti-Interference (A.I.) coil has unique abilities which set this coil apart from the others. Its main purpose is to eliminate any external interference which the metal detectors are susceptible to. The interference can come from Salt Lake hunting, electric fences, power lines, phone towers, metropolitan areas, airports, solar activity etc. By using a coil of this type you can use your detector with little or no interference noise unlike a DD or MONO.
The next benefit is that the performance of the A.I. coil is only approximately 5% down on a DD coil of similar size. Therefore you can be assured that you are getting excellent depth and sensitivity where ever you use this coil type. This coil type has already been used with great success on and around salt lakes and directly under power lines in a gold bearing area. It has helped many obtain more targets in these areas as in the past no detectors could hunt in these locations with any great success. We have many people using these coils as a general hunting coil. We believe it is an essential tool to have in your detecting kit.


With all the great advantages of A.I. coils, I have also heard A.I. coils do not handle high mineralized ground and hotrocks as good as DD coils do, as the only disadvantage otherwise.

you lose heaps of depth with cancel.

old thread but...weekend just gone I got onto some diggings I have been finding gold with the 4500 and 11" mono commander, the gold lead me closer and closer to the nearby power lines and started to become pretty erratic, tried everything and could not tame the machine, so last resort was to get the 11" DD commander on the ground.

Still running pretty badly and getting really close to the lines I decided to flick into cancel to my disgust, thinking I would not get any results I soon found a tiny piece of rubbish which gave me some hope, within 10 minutes I had a 1.1g piece of gold, 5 minutes after that I had a 1.1g gold and ironstone speci....winning I thought.

Within the next few minutes I got another slight signal, after 1 foot of digging I had what I thought was a chunk of steel, after cleaning I found some quartz and realized it was ironstone with a tiny hint gold poking out, the speci is in acid so will see what comes from my 20gram speci from a foot deep produced from that dreaded cancel mode.

The following day I got back into the same area again with the DD in cancel and found another nice 3gram speci which probably holds 0.3g of gold, I have confidence now

Wow Adrian,
i am stunned that you could hear a specie in cancel a foot deep.

Very impressive.



I had the best day(and the most quiet) detecting in cancel second day detecting ever in Laanecoorie.

We went for a afternoon detect and machine was so quiet i was in a heaven.Sure i didn't get any signal not even when i nearly touch the car with coil.


Even i was one day old detectorist i knew something was not right.

The boys play prank on me or i accidentally move switch.(i suspect first option was more likely) but that was the best lesson for me cos it has never ever happened to me again.


Back to topic i found if i come closer to the power lines i lower my detector frequency very low until it gets quiet.Most of the time this worked for me but sure i used a smaller coil to.



GoldEN