I am using DBP 2010 with 1m x 1,2m square coil on regular basis. In my oppinion the beast home made PI ever, quite decent compared with commercial deep seaking PIs, as well as professional ones. It can see large targets down to 4m but i usualy use it with settings to ignore small items up to the size of beer can, with this settings it can go good 2m only, which suits me fine most of thime. No discrimination. The cost of buliding, boxing and battery: around 300EUR. Second best choice of home brew PIs is Sniffer XR71, also known as delta pulse. You can order assembled kit from newhobby.com for around 70 EUR (motherboard only). It would work fine for large targets down to 2m, maybe 3m. You can push it harder, howewer, to reach or even cross 4m depth, but it will get notoriously unstabil. No discrimination.
For around 1000 to 1300 EUR, you can purchase Deep Seaker from Golden Mask. Depth and stability wise is comparable with DBP2010, but it features Fe/ non Fe discrimination - do not count on that information. Non the less it is fine, durable and wery capable detector.
For around 5000 to 6000 EUR, there is a professional Lorentz Deepmax Z1, beaoutifoul kitten, with much better discrimination, noise canceling double coil, gps, data logger, 3d software........etc, etc. This kitten's purr doesn't come chip, howewer.
There is another thing with deep seeking PIs, howewer. You will be forced to gather information about the target you will be looking for, from diferent sources, before you might decide to dig say 3m hole on a terrain accesible by foot only. It is many cubic meters of dirt to remove, and ofently you will be literally able to really feel it.
Feel free to contact me on PM, if you need DBP2010 shematics.
