Chance Pi problem....¿¿¿????

[baum7154]

The following are my latest test results with the new coil:

I put the permanent BNC connector on my feed line and was able to operate the detector at a Guard Interval setting of 16.

At this setting the unit gave first indication detect detection on 0.001" thick aluminum foil at the following distances:

1 square inch - 10" (25 cm) distance, 1/2 square inch - 6" distance (15 cm), 1/4 square inch - 3" (7.5 cm) distance

On an 8.6 grain piece of dental gold it gave 6" (15 cm) first detection distance.

Again these are air tests in my basement and that is not the best environment for this testing but is the best I can do for now.

I will be working on a spiral wound coil as I believe it will allow even lower Guard Interval settings per TEPCO.

[baum7154]

One note on the coil...I did not shield it and probably will not even though the option is still open. I found that the geometry of the spider wound coil does self-shield to a good degree only if you put the outermost winding end to system ground. I just tested this again in my yard this week and the difference was noticeable. Keep track of which wire is 'hot' and which is 'ground'. I did this by putting black & red heat shrink on the ends before I fiberglass encased the coil. I'm not doing further shielding because I don't want to lose any more signal or secondarily to slow the coil down with more capacitance. The twisted pair made up of the continuation of the teflon insulated #26 wire made a significant improvement in the speed and the total lack of any solder at the coil helps too. The twisted pair has not exhibited any detection of metal placed in close contact with it so I believe that it is an acceptable alternative to coax.

Kudos to TEPCO for his comments on setting the critical damping of the coil using a walk-down procedure to get to an operating Guard Interval setting of 10. I read somewhere a long time ago that the Chance must have the 390 ohm damping resistor because the programming was designed for it. NOT TRUE. In spite of that I did try to adjust damping using the BB Sailor method and my scope but could not get improvement. TEPCO greatly simplified the whole process, no scope, just step down to the next lowest GI setting and use the resistor network with a pot described by BB Sailor and adjust until the coil works at it's lowest Guard Interval setting. Hopefully the coil is fast enough to allow operation at the minimum setting of '10'. Then measure the resistor network resistance and put a resistor of that value in it's place. Alternatively, if you think your coil is fast enough just go straight to the '10 setting and adjust till it works. I'll try a spiral coil later because this spider coil now appears to work better than ever. The gold fields will be the final word.

[baum7154]

Tested detector with 1110 ohm coil damping on 1/2' X 1/2" aluminum foil 0.001" thick target tonight on the ground in wet grass and saw no degradation in signal strength from last night's test over wet grass. Got the same 8 signal strength units at close proximity to target. Coil is 8" diameter.

Other targets were tested in air in the basement as follows:
TARGET DISTANCE
1 sq in x .001" thick aluminum foil 9.5"

1/2 sq in Aluminum foil 8"

1/4 sq in Alum foil 7"

1 cm sq Alum foil 4"

US Nickel 12"

US copper Penny 9"

US silver dime 7"

10.5 grain dental gold 6"

8.4 grain dental gold 4"