My detector builds-so far.

[Guest]

Cheers blennus. Not much gold where I am, but now the weather's cooler I can contemplate a few long weekends to the GT, or even some of the SA areas for a day trip/ overnighter. Really the only half decent gold machine I have is the GMT, but I was quite happy with the concentric coil wound from network cable, on the Sniffer- I haven't tried that one on the Surf DD yet- need to make an adaptor plug from AV to Minelab mono pinout(used on my Surf).
If you're going to have a crack at making one, some have pre-made boards with kits to solder/assemble yourself, some have completed boards ready to box up, or you can print and etch a board yourself. I've had a few goes with glossy catalogue paper- worked out the stuff I tried wasn't right, hence a poor job. I got 50 sheets of toner transfer paper for pcb off ebay- did one last night and it turned out perfect. Now I just need to slow down my etchant (hydrochloric/peroxide)- it's a bit savage yet, so I'll halve the Hcl.
It's a real minefield this detector making- so many types and pitfalls, false claims and dumb mistakes.
The one I etched last night is called a Russian Pirate PI, same/similar as a Simpi or Radioskut- the most basic of PIs going. Surf PI is pretty basic too. BFOs are tricky and generally not that good, but I got a good one going- Talking Electronics circuit8- coupled with a good AM radio. Just made another using TL074cn chip by Mamood Alimohammadi. Using a 4 inch ferrite rod wound with enamelled wire as the receiver, but that one took 3 days of fine tuning. VLFs can have many pitfalls for bush mechanics too, that's why PIs are favoured by homebuilders, despite a lot to get your head around initially.
Some kits to look at online are Silverdog, Newhobby, Chemelec. Newhobby(latvia) and 2 others tacoma56(usa) and sinko2012(bulgaria) have stuff on ebay- under metal detector kit. The best sites to join for that stuff I've found so far are Geotech and THunting.

Or just buy one. Probably a Minelab, even the superceded models are good. Or Whites GMT(goldmaster) or Fisher goldbug2. They're probably your best bets. There are a plethora of different, obselete and little known detectors, many cannot handle Oz conditions, but some can.

I have the Newhobby NH5 assembled board coming this week, and the Pirate to make. I'm looking at the Hammerhead next for a complete build and sinkos Vandal pulse 2 as a completed board. Also NHs Magnum VLF. Sinko also has a complete(unknown) VLF for auction on ebay, starting at $360(?).
There is no shortage of ideas and designs out there- you just have to trawl through the waffle sometimes.

 

[TheWolf]

Tim - you've inspired me! I'm going to take a crack at a surf PI DD myself as a starting point, and then move on from there! There is so much info out there ... I didn't even realise it is "a thing". I'll let you know how I go...
Cheers,
M

 

[Guest]

Howdy Wolf. I just finished a Russian Pirate PI-MD, from etching the board to full build. I haven't painted the brackets etc.yet though. The coil I made for it was 6 inch ID, 3 winds of Cat5 networking cable, twisted around each other. 8 strands, 3 winds= 24winds. I connect orange to orange/white to green to green/white to blue to blue/white to brown to brown/white. Orange is pos/start, brown/white is neg/finish. At this size it was 450uH, but once bound with electrical tape it was 500uH.
Out of interest I tried it on the Surf pro DD. The Pirate is a bare-bones basic, but on the Surf this coil had a strong signal air test, 2g flour gold at 4 inches!!
The Surf I have is the squareboard from Tacoma56 on Ebay- I bought it assembled and tested. He has kits advertised as well, but you will need some skills and at least the basic measurement capabilities and equipment and settings to be successful.
When you trawl through Geotech, THunting and the other websites you will notice 90% of posts are from unsuccessful builders seeking help, and usually the info they seek is only a few pages back, or they have made a silly mistake, like a reversed diode or xxxK resistor instead of xxxR.
Some ongoing info on the Pirate is here in "today I made".

I myself am only just staring to glean the differences and similarities between the plethora of ICs - timers, op-amps, comparators etc., and their different wirings for different applications. For me it's not enough to build the board- I want to be able to make a working machine from a handful of parts, design and etch my own boards and make the completed detector from some basic hardware supplies. I make my brackets and armrests from pvc sewer pipe, cut, flattened, templated and shaped with a heat gun. Next is to make a former/formers to make coils housings and covers this way too.
Here's the unfinished Pirate.

Designing the Sniffer to be compact.

The Sniffer XR71 and the Surf Pro.