Detector for sea beaches UK

[Koala]

I have just finished silverdogs IDX PRO. More than satisfied with the results on fields. I now want to build a detector for general sea beach detecting. Tried the IDX and had some finds But would like to work the salt water channels. The IDX works well enough in damp sand but fails if there is salt water in pools under the surface unless I am doing something wrong. Guessing I need to build a PI. Would like to use a silverdogs PCB again.

Seen the question has been asked a few years ago don't think the Baracuda was around

Three PCB that are listed

Baracuda Legend PCB
Hammerhead I Rev D
Surf Pi 1.2 Longboard

Reading the forum people who have built the Baracuda and Surf seem to prefer the Baracuda. I was wondering how the Hammerhead compares.

[golfnut]

I think the vlfs like the IDX should be modifyable with small redesign to enable use on wet sand.

The goldmaxx power is a VLF and that has enough throw on the geb system to integrate out the geb return from wet sand - so Im sure it can be done.


I dont know what the phase of wet sand is, so I dont know if you need the the GEB gating earlier or later.


Some one on here may have the info we need.


S

[Koala]

I think the vlfs like the IDX should be modifyable with small redesign to enable use on wet sand.

The goldmaxx power is a VLF and that has enough throw on the geb system to integrate out the geb return from wet sand - so Im sure it can be done.


I dont know what the phase of wet sand is, so I dont know if you need the the GEB gating earlier or later.


Some one on here may have the info we need.


S

Tried on a couple of Norfolk beaches. First beach was fine in damp and dry targets up to spade depth (11"). Second beach different story. Many false signals nearly every step. Second swing there would be no target. Seems to be pools of water under the surface. Found a small batch of coins pulled 3 out sure there were more MD was very very unstable. Did find a large iron? target at over 20" deep it was about 3" diameter and at lease 2 foot long spent over 10 minutes trying to dig it out but gave up as the hole kept collapsing.

Will not give up with the MD on the beach yet.

Will be near Blackpool sometime next week so will have another go.

Can someone tell me the best way to set the MD for wet sand

[golfnut]

A lot of modern commercial machines get confused by large rusty iron also.


I put a momentary action flip switch on my idx on the disc pot to tggle quickly between all metal and a previously set disc setting.

I hover over a large target high up sometimes a foot or more and when it starts to dissaper in all metal - so its detectable but weak - then flip to disc and 60% of the time it fades to a snap or a click and then recheck by letting go of the switch to a full tone - that way its deep rusty iron and you move on.


The mod is just a switch and 3 wires tacked on.


You get the advantage of about 1 1/2" extra depth and a correspondingly larger foot print / sweet spot. Less likely to miss stuff.



S

[Koala]

The mod is just a switch and 3 wires tacked on.
You get the advantage of about 1 1/2" extra depth and a correspondingly larger foot print / sweet spot. Less likely to miss stuff.
S

I already have a PP/All metal mode toggle switch. Nice tip for rejecting large iron.

Don't understand the last statement larger sweet spot is that in all metal or disc. "I will have to try a few targets at home"

[golfnut]

In all metal you dont loose any of the Non Fe signal as you would if the Disc gating is wound out to not gate early iron signals.

If you reject all traces of the early iron signals you loose some of the non Fe signal energy also, as the signals partially overlap.



If you get more signal through you get more depth, and the edges of the coil get a little more signal too - like the drawing.



S

[Koala]

Thanks for the explanation now I understand

Unfortunately the only way I can use the MD to run in damp sand is to run in disc mode and wind the disc up to reject some of the salt. "loose a lot of depth though and still unstable"

In all metal mode it way way to unstable. Beep several times per sweep if you sweep again beeps in a different place. "have to retry with another coil" On my old 6000D TR mode works very well in saltwater. Press the button a couple of times and keep the coil the same distance from the ground moving the coil slowly an increase in tone is easily spotted. Disc mode also works but gives you arm ache as needs a very fast sweep speed to eliminate false signals. Dug some light black rocks that give a good signal in Disc mode. In all metal mode they have an opposite affect on the threshold sound i.e. goes quieter. Fetch some home to test with. Found if ground balance to these they have no affect on disc or PP mode its not that far from normal ground would it be better for me to ground balance to these

Wish I lived closer to the beach so I can get use to the MD and optimize it's settings. Next time I will take a smaller coil and try a quicker sweep speed as per 6000D.

[golfnut]

These machines will not work on wet sand - there is no combination of settings.

There may be a design tweak where we can redesign the geb gating position so it straddles the zero crossings of the signal from wet sand.


The first hurdle is to find where salt phase lives and devise a test for it in the absence of having wet sand in my garage.

Fake soil is easy using ferrite..


If the phase of wet sand is close to non Fe targets, then this may be the reason that a simple solution for wet sand is not offered on basic vlfs.

S

[Koala]

Been metal detecting in the dark at the beach. Only took the 8" standard coil. Got a modern 2p, silver plated tea spoon minus its silver, some .303 bullets, some .50 bullets, a .303 cartridge, 3 bottle tops. Could have more .50 cal bullets as there was several targets per swing in a tight area of the beach but moved to try elsewhere.

Tested different parts of the beach. Shallow water over sand very stable. Damp sand stable. Dry sand very stable. The boarder between dry and damp very unstable. Dry pebbles stable-ish. Shallow water over pebbles unstable. Areas that are a mixture of dry and damp totally unusable.

The area between dry and damp can be worked by sweeping parallel to the boarder and walking sideways

Looks like it's back to the original question for areas of the beach where the IDX does not work.

Baracuda Legend PCB
Hammerhead I Rev D
Surf Pi 1.2 Longboard



Great night though. Some kind of biofluorescence every time I put the spade in or walk on the sand it would sparkle. Then seen an owl,fox,stoat and badge on the way home.

[Davor]

Gee, what kind of beach was that? I was completely baffled when I found 2 WW1 7.62mm cartridges (apparently from opposing sides). Later on I learned that no history book describes WW1 of these areas - at all - as it never happened.
You must live in some very dangerous place!

[Altra]

Great night though. Some kind of biofluorescence every time I put the spade in or walk on the sand it would sparkle. Then seen an owl,fox,stoat and badge on the way home.

Google "Plankton Glow" its quite a sight.

[Koala]

Gee, what kind of beach was that? I was completely baffled when I found 2 WW1 7.62mm cartridges (apparently from opposing sides). Later on I learned that no history book describes WW1 of these areas - at all - as it never happened.
You must live in some very dangerous place!

Beach was used for a firing range for Mustangs and Spitfires during WWII. Thousands of spent bullets all too easy to find. Spitfires were original fitted with 303 until they found that the German planes hit were still flying home. Only ever found .303 cartridges though does anyone know if the used .50 cartridges were retained. .303 cartridges are made from poor material only the bottom half survives.

[Koala]

Google "Plankton Glow" its quite a sight.

Worth going to see with out the metal detector.

Did scare me the first time as I diging near spent bullets and thought I saw some sparks. Not quite fully dark yet. Then I thought it was a trick of the light from the moon. When fully dark very spectacular every step had a sparkle and glow to it and every spade dig was like your own sparkler. Would never have see it except for metal detecting

[Koala]

Conclusion

Some parts of the beach are near to imposable to detect with the IDX (areas hot rocks or mixed damp and dry areas) Still think I need to build a different MD for these areas?

8" factory concentric is much more stable than my homemade 27 cm DD in damp and wet areas. (do I need to adjust the receive cap)

Plain sand covered in saltwater plus 8" factory coil equals no chatter or false signals able to run MD at full throttle settings (did not expect this)

27 cm DD is much better in dry sand for coin size targets. Be prepared to dig deep big holes though can be slow going. Like the coverage of the DD though.

[Davor]

IDX is not much of a detector for beaches , first because it has a fixed GB, and second, because even if you apply some Mr. Bill's mods, you'll still be short of a real beach GB range. In fact all of the popular builds are missing the beach GB setting.

It can be done though.