Difference between Mono and DD coils? When to use?

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undertaker

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As I've posted in another thread, I recently received a Minelab GPX 5000 for my birthday present. However, I'm a bit confused about one thing...

When do you use a Monoloop coil and when do you use a double D? If I go to a bush for example and I don't want to carry the other coil with me everywhere (as it can be bothersome), which coil should I use?

Also, is it possible to use a Monoloop coil on DD setting on the control pack and vice versa? Sorry, I'm still just getting the hang of all the different functions and settings and feel it will take me some time to master this.

Thanks
 
The gpx 5000 is designed to be used with a mono, you should be using one of these most of the time. The only time I see a DD needed is on salt lakes or near powerlines.
You can use a DD in mono setting and it only uses half the coil. No point really.

DD
 
The mono is the coil of choice for the 5000. But the DD certainly has it's place. You will hear the saying 'dig every signal'. And digging every signal soon gets old especially in trashy areas. That's when I prefer to swap my mono for a DD and use discriminate. Others will, no doubt, disagree. But I have the gold to show for it and from areas that were littered with trash. The DD will also let you get closer to power, into places the mono can't go. When going 'bush' I still take both types of coil. I mainly use the mono but have the DD in my vehicle, or daypack, so it's handy if needed. The mono cannot be used in DD function. The DD can, however, be run in mono. You do have to keep in mind, when using the mono, that each overlapping sweep of the coil must be a little greater than needed when using the DD. That's because the signal the mono generates is cone-shaped, tapers to a 'point', whereas the DD punches straight down.

MONO COILS Vs DD COILS

MONO advantages

1. they will usually get better depth over a dd coil
2. they are more sensitive than a dd coil
3. they are sensitive around the entire perimeter of the coil
4. the bigger mono coils are usually much lighter than the dd coils of the same size
5. Work better on the later gp series and gpx series detectors
6. Easier to pinpoint a target with
7. better for probing under scrub or around trees due to being sensitive around the perimeter

DD advantages

1. dd coils are quieter in highly mineralised ground
2. they can be switched from dd to psuedo mono as required
3. they better suit the earlier model sd and gp detectors
4. they can be used in some areas that mono coils are quite useless
5. can be used in discrimination mode
6. discrimination mode still works on pseudo mono setting

DD coil is generally heavier than a mono
 
mozzie1957 said:
The mono is the coil of choice for the 5000. But the DD certainly has it's place. You will hear the saying 'dig every signal'. And digging every signal soon gets old especially in trashy areas. That's when I prefer to swap my mono for a DD and use discriminate. Others will, no doubt, disagree. But I have the gold to show for it and from areas that were littered with trash. The DD will also let you get closer to power, into places the mono can't go. When going 'bush' I still take both types of coil. I mainly use the mono but have the DD in my vehicle, or daypack, so it's handy if needed. The mono cannot be used in DD function. The DD can, however, be run in mono. You do have to keep in mind, when using the mono, that each overlapping sweep of the coil must be a little greater than needed when using the DD. That's because the signal the mono generates is cone-shaped, tapers to a 'point', whereas the DD punches straight down.

MONO COILS Vs DD COILS

MONO advantages

1. they will usually get better depth over a dd coil
2. they are more sensitive than a dd coil
3. they are sensitive around the entire perimeter of the coil
4. the bigger mono coils are usually much lighter than the dd coils of the same size
5. Work better on the later gp series and gpx series detectors
6. Easier to pinpoint a target with
7. better for probing under scrub or around trees due to being sensitive around the perimeter

DD advantages

1. dd coils are quieter in highly mineralised ground
2. they can be switched from dd to psuedo mono as required
3. they better suit the earlier model sd and gp detectors
4. they can be used in some areas that mono coils are quite useless
5. can be used in discrimination mode
6. discrimination mode still works on pseudo mono setting

DD coil is generally heavier than a mono
Click to expand...

Thanks so much for your detailed reply.

So, if I go to a very large area, regarding the sweeps, would it be more beneficial to use the mono coil?
 
From my perspective, if you want to cover a larger area, quicker, to see if there is anything there a DD will not require as much overlap and is quicker than a Mono. However as stated it doesn't go quite as deep for the same size coil and is not quite as sensitive.

If you get a couple of hits, then that's the time to swap to a Mono and do it slower, deeper and with more sensitivity.

Bare in mind, a larger coil will get bigger pieces, deeper, but may miss the shallow smaller bits.

If you really want to cover a patch and it's open enough to do so;

Grid the area and start with a 14 to 198" DD or the largest you have, if you find something then,
Swap to the largest Mono you have and go over the area again,
Finally swap to a smaller Mono, like a 8" or an equivalent elliptical coil and go over the area again. Takes the longest time to do properly.

It really is down to how thorough and how much time you want to spend, as well as what you have available in the coil ammo box.
 
I always carry both coil types with me in a back pack if I'm trying out new areas as it's not the first time I've had to make the switch while out bush. I think it's a good idea to take both with you when trying a new area and once you're familiar with the ground and find which coil is most suitable for the conditions you can leave either the DD/mono at home.
 
condor22 said:
From my perspective, if you want to cover a larger area, quicker, to see if there is anything there a DD will not require as much overlap and is quicker than a Mono. However as stated it doesn't go quite as deep for the same size coil and is not quite as sensitive.

If you get a couple of hits, then that's the time to swap to a Mono and do it slower, deeper and with more sensitivity.

Bare in mind, a larger coil will get bigger pieces, deeper, but may miss the shallow smaller bits.

If you really want to cover a patch and it's open enough to do so;

Grid the area and start with a 14 to 198" DD or the largest you have, if you find something then,
Swap to the largest Mono you have and go over the area again,
Finally swap to a smaller Mono, like a 8" or an equivalent elliptical coil and go over the area again. Takes the longest time to do properly.

It really is down to how thorough and how much time you want to spend, as well as what you have available in the coil ammo box.
Click to expand...

If you use a DD to do this you may not get a hit & walk away from an area that is holding gold.
If you want to grid an area quickly you could do it with a larger mono, like a 14/16/18/20", to start with which will give you a much better chance of not only finding deeper gold but the mono will give you much better sensitivity to smaller shallow gold as well, even with a larger coil.
Using a DD first, in an area you can run mono's, seems a bit counterproductive due to the possibility of missing gold then also having to redo if you do happen to find a bit which makes things slower not quicker.
For mine using a DD on a GPX is a last resort option I.e.:
-high interference areas
-high trash areas/relic hunting for discrimination
-extreme ground noise from conductivity (salt), minerals or both that timings won't remedy
 
undertaker said:
mozzie1957 said:
The mono is the coil of choice for the 5000. But the DD certainly has it's place. You will hear the saying 'dig every signal'. And digging every signal soon gets old especially in trashy areas. That's when I prefer to swap my mono for a DD and use discriminate. Others will, no doubt, disagree. But I have the gold to show for it and from areas that were littered with trash. The DD will also let you get closer to power, into places the mono can't go. When going 'bush' I still take both types of coil. I mainly use the mono but have the DD in my vehicle, or daypack, so it's handy if needed. The mono cannot be used in DD function. The DD can, however, be run in mono. You do have to keep in mind, when using the mono, that each overlapping sweep of the coil must be a little greater than needed when using the DD. That's because the signal the mono generates is cone-shaped, tapers to a 'point', whereas the DD punches straight down.

MONO COILS Vs DD COILS

MONO advantages

1. they will usually get better depth over a dd coil
2. they are more sensitive than a dd coil
3. they are sensitive around the entire perimeter of the coil
4. the bigger mono coils are usually much lighter than the dd coils of the same size
5. Work better on the later gp series and gpx series detectors
6. Easier to pinpoint a target with
7. better for probing under scrub or around trees due to being sensitive around the perimeter

DD advantages

1. dd coils are quieter in highly mineralised ground
2. they can be switched from dd to psuedo mono as required
3. they better suit the earlier model sd and gp detectors
4. they can be used in some areas that mono coils are quite useless
5. can be used in discrimination mode
6. discrimination mode still works on pseudo mono setting

DD coil is generally heavier than a mono
Click to expand...

Thanks so much for your detailed reply.

So, if I go to a very large area, regarding the sweeps, would it be more beneficial to use the mono coil?
Click to expand...

The DD will allow you to cover the area a little quicker as your overlapping sweeps will not be as great as required when using the mono. But the mono will
probe deeper than the DD. Personally I use my 18" mono when in fairly large open areas.
 
I have read quite few comments about how much deeper can Mono coil detect compare to DD. But did any one actually tested same size Mono and DD coils with same detector on same target? It would be interesting to know the results. I can't do the test as I don't have two same coils in Mono and DD.
I have seen video where 6" X Terra coil did pick 5 cents coin deeper then 10x5 so called gold coil. But both of them were DD.
Karl
 
I'll test the 11" DD Super gold Search vs 11" Mono Commander right now if you like on a 2200D

Give me 10 mins :)

11" DD, 0.52g nugget (9cm)
11" mono 0.52g nugget (14cm)

11" DD, 3.7g nugget (16-17cm)
11" mono 3.7g nugget (19-21cm)

2200D stock machine, others will differ greatly..
 
Good question. I've never checked any targets but people have told me a general rule of thumb is that the DD will detect approx. the same depth as the next size down mono i.e.

18" DD > 14-16" Mono
14-16" DD > 11-12" Mono
11-12"DD > 8" Mono
etc.

Would be interesting to see actual results but by design mono's should/would be punching deeper. How much by I don't know?? I guess even if it was only an inch or two that is an advantage.
I wouldn't be too worried about that 11" DD you got Karl. They still punch deep enough & I have dug some bloody big holes using one + my old SD2200D. One hole I remember fondly, NOT :lol:, was about 2 foot down (my pick handle is about 650mm & the hole was nearly as deep as it is long). Beautiful woowoo sound from the surface & the closer I got the louder it got. Thought this is either an ounce + nuggy or a flamin' horse shoe. Ended up being a metal boot heel off an old timers boot - took me about 20-30 mins to dig up in hard ground.
 
Not worried,just interested. I'm got lot of experience with small DD coil on X Terra. And no know the disappointment of digging in rock hard ground in the middle of summer, just to find huge horse shoe about 45 cm down.
Karl
 
Yeah sounds about right. The DD's need to be a little larger to match the mono's for depth in quiet ground. The 18x15" detech coil on the 4500 is my fave if I want the best of both worlds. Super light weight and comparable in depth to my 14" round mono until extreme mineralization is encountered and it gains the advantage..
 
Karl, most people reiterate Mono vs DD depth advantages from books, experts etc. I have never seen a gold in situ test between the two and I have never done in ground tests between the two. By design a mono should go deeper, but if that mono coil is running noisy and one has exhausted all options to control the coil (smooth threshold) then you would have to change over and run a DD coil? I have seen on the web, Air tests, test beds comparing the two. These tests give some idea, but there is no substitute for real digs with gold in situ.

I know a bloke who dug 4ft down for a oil filter once and it was all caught on camera. I don't blame him though his wife scoured a 26 oncer in the same area the day before. :)
 
Roscoe said:
Karl, most people reiterate Mono vs DD depth advantages from books, experts etc. I have never seen a gold in situ test between the two and I have never done in ground tests between the two. By design a mono should go deeper, but if that mono coil is running noisy and one has exhausted all options to control the coil (smooth threshold) then you would have to change over and run a DD coil? I have seen on the web, Air tests, test beds comparing the two. These tests give some idea, but there is no substitute for real digs with gold in situ.

I know a bloke who dug 4ft down for a oil filter once and it was all caught on camera. I don't blame him though his wife scoured a 26 oncer in the same area the day before. :)
Click to expand...

And that is exactly why did I ask. I have been working in electronics most of my life and I'm very much aware that theory and the practical application do not necessary give same results. Hitting the target with Mono coil at maximum depth is to some of the extent question of luck. The 12" mono coil will have deepest detecting spot of around 5" diameter or less . I have not seen many people to overlap their swings by that much. And if you miss your deep target by couple inches, there goes mono coil depth advantage.
Karl,
 
I have seen some gold and junk, been dug up deeper than i would of thought/assumed the coils could penetrate, eg: a 6" old aluminium pot faintly picked up (after it was dug) on the measuring tape at 1250mm with a gpx 4000 and eliptical mono, from memory about a 14x10 14x12, once it was removed from the ground a air test was done at the same height and zip, nothing at all, go figure 8)
 
Between the period of the Minelab 2000 to the 2200 lots of prospectors used large DD coils in Victoria in spots where the ground was very noisy. Some diggings that turned up the deeper gravel with lots of iron minerals were impossible to use a mono on. DD coils definitely had a depth advantage because the monos were swamped with noise. Its changed since then but i am sure there is some ground where some forum members are finding deeper results with a DD???. The SDC may have put another nail in the DD coffin for shallower gold in very noisy ground anyway.
RDD
 
I just finished bit of testing of new 11" DD coil. The targets were 0.6 and 6,5 grams pieces of lead, buried in 8 cm and 12 cm in the ground. The SPP ground balanced on default setting. The White's 7.5" mono coil picked 6,5 grams but failed to sound on 0.6 grams.
The Minelab Commander DD picked up both targets with clear signal.
Karl
 

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