Bigger coil for Surfmaster ¿?

[plumabob]

Hi All,

I can back up hobbes_lives results of 13 inches on an air-tested nickel. I also have built a Surf PI from silverdog. After 3-4 coil tries I hit on a 9.5 that does indeed see nickels at 15 inches. Since that success I have built a 13 x 11 mono that hits nickels at 16 inches in air testing. Two types of wire were used...stranded teflon 22awg on the 9.5 and 22/36 litz for the 13 x 11, but my parameters are close to identical. .290uh and just under 1 ohm R. I'm using 3M #1190 copper fabric tape for my shield. I closely followed BB Sailors coil building techniques by the way. I am sampling at just under 10us, where the deepest targets are heard.

One more point, the signal at 15-16 inches is not blasting. It's a faint but very noticeable and definitely a digging target. I also use headphones. I do not think you will hear the deepest targets without them.

Bob

[bklein]

It's a Surf PI Pro, the predecessor to the Dual Field. The larger coil provides more depth on rings and coin-sized objects than the stock 9.5" coil, however, it also picks up more interference from wave action in the surf.

I had a chance to use a Dual Field in the surf for a couple of hours some time ago. The Dual Field definitely seemed quieter than the Surf PI Pro. Whether it's due to the new coil configuration, or due to modifications that Whites made to the circuitry, I don't know. I didn't get to use it long enough to really get a sense of whether the machine is more or less sensitive to coin-sized objects, so I can't provide much more feedback on that point.

Hi,
As you may have read elsewhere I too have obtained a Surf PI Pro - but it was water-damaged in the coil, feedline, and electronics. I replaced the controls, cleaned the pcb and repaired traces, cut back the feedline on both ends, and got inside the coil housing to reconnect its broken connections. Now I get it to work, but really touchy on the trimpots - I haven't yet sat it down with a scope to tweak. It seems to jump in and out of functionality on me like the timing may be moving into the flyback decay portion (usually just after I put it all back together in the housing). I also can't make much sense out of the controls. The gain doesn't really seem to have much benefit - I would think there would be like an oversaturation point but there isn't. The tuner I think is to set a background level but this doesn't seem to improve sensitivity so what's the point? I also have a surf pi with 950 coil and it has different circuitry (like the surfmaster designs here). By chance did you figure out what circuit differences the pro has? Any recommendations on mods I should try? When the pro is working it seems to have the same sensitivity to a mens gold ring - about 7-9". It doesn't have the motorboating background tone that the 950 has. The pro has several unpopulated component places - is this how yours is as well?

Barry