GP 3500 Current Status In The Line Up

[PhaseTech]

Oh for sure. In very mild wash, you can put a new gen spiral coil on the 3500, run it in Sens and Deep and it will pretty much match what a GPX can do, minus the extra bit you can squeeze out of a 4500 and 5000. 

I hope you didn't just leave your 3000 in Sensitive though, as Normal has a clear advantage over the more conductive bits. Even some as small as say a flat half gram piece. 

[Joe76]

On 4/2/2018 at 10:18 PM, PhaseTech said:

Here's what worked for me when I was swinging a 3500. These settings will work equally well with small - medium mono coils and the stock DD coil. 

Set your controls to the following settings:

Signal control - just off maximum (in noisy environments you may need to turn it down to 2 o'clock) 
Tone - the highest setting you are comfortable with. My preference was 3-4 o'clock
Volume - 4 o'clock
Threshold - just audible, but smooth - if it is breaking up it is too low
Coil - Mono
Soil - Sensitive
Ground - Fixed

If the ground allows it you can use Deep boost, but if it upsets the stability of the threshold, use Normal. 

Ground Balance as often as practical, and avoid running in Tracking if at all possible. 

Perform an Auto Tune as often as necessary. The most important aspect to the tuning process is to ensure the coil is held motionless. The easiest method I find is to turn the coil at 90 deg. and find the loudest direction of interference, and then place the whole detector on the ground, with the coil still vertical. With the GP 3500, you can keep the detector tuned by using the Manual Tune control. 

When you get a faint signal that you suspect may be a small nugget, play with the audio controls and see if a few small tweaks improve the signal response.
 

Hi Nenad,

I have a question about running a gp3500 in tracking, I have a patch I found some years ago when I was using my gpx5000 with some really nice gold coming off it, like the 2 ounce bit in my profile pic. The ground is so hot and variable that enhance & fine gold struggled even dialling down settings. A took a mate out there just for a day so he could find a bit with his ZED & it too had trouble over the same ground having to drop sensitivity right back to try & cope. I haven't encountered groud like it before. Since then I sold my 5k through not being able to get out and use it but still own a gp3500. Now I am back on the hunt again, I was wondering if you had any experience using a gp3500 running in tracking using a DD coil opposed to fixed & if this may work in this situation as this ground seems to be nearly impossible to work at times.

I did some tests with a 0.3 piece using my Detech 15" spiral dd running in tracking & what I found I couldn't track out the nugget in dd mode. I'm yet to test my Detech 11" spiral mono using tracking. But I am hopeful over this super hot ground the gp3500 may have a chance if I can use tracking using a dd coil. If you have any advice you could share with me using the 35, it would be much appreciated.

Cheers Joe

[Joe76]

On 4/10/2018 at 10:50 PM, PhaseTech said:

The tracking has always been good, it is just the danger of tracking out a target is always greater when using a mono coil. Small low conductive targets, and the higher the mineralisation, the greater the risk! 

On the SD2200 series, the tracking was a slower rate, and as the 2200 hates mono coils (except for really mild ground) most people never took it out of tracking.  On the GP extreme and 3000 it was a faster rate, I guess it had to be because the machines were more sensitive. The Level adjust allowed the user to control the tracking to some extent, but most found this confusing, so 3 x speeds were introduced on the 3500 (with the Level Adjust being pre-set). 

Using a DD coil, I have never had a nugget track out (that I've noticed), but have noticed several times using a Mono. Not instantaneous, maybe 5-7 sweeps and the target was totally gone. Re-balance off to the side, check again, and yep target still there. Dig it up, and sure enough it's gold. This is reduced with the slower tracking speeds, but the only way to remove the risk all-together is to use Fixed and re-balance as often as you can remember. 

Great explanation, the gp3500 is still a very good detector along with the earlier models such as the sd2200. I remember a trip to Flat creek station in 2009 near George town NTH QLD. The camp site was full & there were plenty of Gpx 4500's & 4000's being used. I was the only one there with a Sd2200. After setting up camp & introducing my self with some of the prospectors It became apparent that nobody had found any gold in days, this was certainly discouraging for me that I was about to start detecting with a Sd2200 over where 4500's had already been hammering. 

But after driving nearly 7 hours to go prospecting I wasn't about to give up that easily. So I threw on my harness and headed west straight through the main diggings going towards the Gilbert River, in the hope of finding ground out that might give up a nugget here & there. Well I only made it 50m from camp when I got a soft signal through my earphones, I don't know how deep it was, but it was a 9 gram nugget at good depth. I was very surprised considering there were so many gpx detectors flogging this area for days.  It wasn't until a couple of years later I realised why nobody had found that nugget before i did & I think it came down to the fact most were probably using smooth timings to quieten the ground down and the nugget I found was just out of reach for the newer machines. The Sd2200 with no choice but the more powerful normal timing, was punching deeper on the bigger solid bits at depth.

As soon as i found that nugget I walked straight back to the camp site to show everyone what i just found with the 2200, I don't think too many were very impressed with me lol. But it just goes to show how good the older machines still are, especially the Gp3500 if your willing to put the time in.

 

 

[PhaseTech]

On 5/19/2019 at 10:00 PM, Joe76 said:

Hi Nenad,

I have a question about running a gp3500 in tracking, I have a patch I found some years ago when I was using my gpx5000 with some really nice gold coming off it, like the 2 ounce bit in my profile pic. The ground is so hot and variable that enhance & fine gold struggled even dialling down settings. A took a mate out there just for a day so he could find a bit with his ZED & it too had trouble over the same ground having to drop sensitivity right back to try & cope. I haven't encountered groud like it before. Since then I sold my 5k through not being able to get out and use it but still own a gp3500. Now I am back on the hunt again, I was wondering if you had any experience using a gp3500 running in tracking using a DD coil opposed to fixed & if this may work in this situation as this ground seems to be nearly impossible to work at times.

I did some tests with a 0.3 piece using my Detech 15" spiral dd running in tracking & what I found I couldn't track out the nugget in dd mode. I'm yet to test my Detech 11" spiral mono using tracking. But I am hopeful over this super hot ground the gp3500 may have a chance if I can use tracking using a dd coil. If you have any advice you could share with me using the 35, it would be much appreciated.

Cheers Joe

Hi Joe, 

A DD coil in Fast tracking is your best bet for hot ground. A big normal wound coil like a 18" DD Commander will handle super hot ground very well. If you are after depth, and the area is known for big deep lumps try Deep and Salt timing, especially with the 15" Detech which is a very sensitive DD. 

Cheers, Nenad

[Joe76]

Hey thanks, Nenad. I will give that a go for sure. I've never used salt timing before so It will be interesting to see how it handles the ground That maybe the problem the soil maybe be high in salt. As a interesting note the ground was once the ocean floor so that would make sense. Some people on hear maybe familiar with the area it's a town called Chilligoe west of Cairns NTH QLD it's not known for gold so much as it is mostly marble & granite country with high limestone bluffs scattered across the landscape & if your into exploring caves there's some really deep ones. Anyways I'll give that a crack, it will be good opportunity to test the NF 25" dd against the 15" dd ultimate

Cheers, Joe

[PhaseTech]

Cool, sounds like an interesting area. 

[Joe76]

On 4/2/2018 at 10:18 PM, PhaseTech said:

Here's what worked for me when I was swinging a 3500. These settings will work equally well with small - medium mono coils and the stock DD coil. 

Set your controls to the following settings:

Signal control - just off maximum (in noisy environments you may need to turn it down to 2 o'clock) 
Tone - the highest setting you are comfortable with. My preference was 3-4 o'clock
Volume - 4 o'clock
Threshold - just audible, but smooth - if it is breaking up it is too low
Coil - Mono
Soil - Sensitive
Ground - Fixed

If the ground allows it you can use Deep boost, but if it upsets the stability of the threshold, use Normal. 

Ground Balance as often as practical, and avoid running in Tracking if at all possible. 

Perform an Auto Tune as often as necessary. The most important aspect to the tuning process is to ensure the coil is held motionless. The easiest method I find is to turn the coil at 90 deg. and find the loudest direction of interference, and then place the whole detector on the ground, with the coil still vertical. With the GP 3500, you can keep the detector tuned by using the Manual Tune control. 

When you get a faint signal that you suspect may be a small nugget, play with the audio controls and see if a few small tweaks improve the signal response.
 

G'day, I Just bought a Detech 8" dd coil from you today, I will be keen to see how it goes on the 35, if I can run it in mono over my patch that will be a bonus. One thing I have noticed with the signal control on the 35 is how the threshold behaves from anti clock wise to full clock wise position. At the full signal position the detector seems to be smoother & quieter than opposite position where the threshold volume appears to sound louder with less stability. Why the target response is reduced is obvious but the instability with the signal control wound back makes no sense to me.

I found If I run the signal back a touch from max & lift the threshold a little it purrs along nicely without going into overload when retrieving targets.

[Johnnygoldseeker]

Sorry to drag up an old thread but im looking at a 3500. I know its discontinued but if buying what should i try to pay at this time? Is $1000 high w a nugget finder coil? Any help is appreciated!

[DigsAlot]

5 hours ago, Johnnygoldseeker said:

Sorry to drag up an old thread but im looking at a 3500. I know its discontinued but if buying what should i try to pay at this time? Is $1000 high w a nugget finder coil? Any help is appreciated!

No worries Johnny. Old threads are just paused discussion on this forum. As for the price of the unit I am not sure what what your area price would be. You could check ebay or ask Rob as he is a used dealer he would know more then i. However if you do get it let us know. As you can see lots of people really liked that unit.