TEFLON MULTI STRAND WIRE QUESTION

[daverave]

im getting a bit old at 55 years old to dig deep holes and i really feel it as i try and dig them...lots i just have to leave and go for more easy targets....can you tell me more about this soda can test ???

[6666]

Hi Dave sure.
BTW my sand scoop is quite large the basket can hold a 2 litre and a 1.25 litre plastic coke bottle at the same time , so you can get an idea of the deep holes it can dig.

A few years ago while hunting on a wet beach (laping water) useing a commercially made detector, I dug up a crushed coke can at 20 inches, or 51cm's .
I thought that was a good depth for that type of target, I reburied it and tested a second detector , both detectors found the can very easy, but close to the limits of the machines, and this test became My standard comparison test for the beach.

So when I make new coils or do mods to my home made detectors etc or buy a new commercially made detector I test them by burying a crushed coke can at 20 inches, the good thing about this simple test is anybody, anywhere can do it.
Cheers

[daverave]

i really need to get myself a good sand scoop but very expensive here in the uk at around $200 so ive asked my wife to buy me one for christmas....see what happens at present im using small spade but as you know the holes fill with water so quick and target so hard to locate...and if really deep i just give up and move on....wish i was 21 again

[6666]

Hi Dave I hope you get your Xmas scoop.

[bbsailor]

i really need to get myself a good sand scoop but very expensive here in the uk at around $200 so ive asked my wife to buy me one for christmas....see what happens at present im using small spade but as you know the holes fill with water so quick and target so hard to locate...and if really deep i just give up and move on....wish i was 21 again

Daverave,

Here is an alternative to an expensive sand scoop that works very well on the beach. I call it a "beach basket". It is made of common galvanized wire where the wire makes a mesh of about .5 inch or about 12mm squares. The diagonal space of the square mesh size should not pass the smallest coin you may find. I made a 12 inch wide by 12 inch tall round basket by bending a flexible plastic tube or pipe to form the 12 inch top rim to form the top opening. Then with the basket sitting on the ground with the opening facing you, slice the horizontal wires of alternate columns to make a series of ladder-like extensions long enough to wrap around the plastic tube/pipe. This bending cannot be done if the mesh is not cut as I describe. Use a needle nose pliars to twist the end of the ladder-like lextension to secure it around the pipe. Before doing this however, secure the 12 inch vertical edge of the cylinder together the same way by interlocking the wire ends.

Cut a round piece little oversize and interlock the galvanized wires and twist the ends together to add the bottom to the basket. Put a short rope across the top opening and tie about a 4 foot line to the center and make a hoop out of a wire coat hanger or similar metal wire. Hook to your belt or drag it behing you along with a long wood handle shovel. You acn even hook the bottom of the basket and sling it over your shoulder to keep it far away from your coil so as not to detect the basket. I drag the basket and shover in my free arm, leaving a mark in the sand to show where I have already detected.

When find a target I place the basket about 3 feet from the target and then dig it out of the sand with the shovel. I place each dig of sand around the circumference of the hole top and stop digging when I no longer hear the target in the hole. Then it must be in one of the piles around the top of the hole. Then I scan the top piles to locate the target and use the shovel to deposit it in the basket. When I find a hot spot with many targets, I put as many targets in the basket until it is full, then I shake it once to recover all the targets at once. This uses less energy that shaking the basket for each single target.

By listening to the amplitude of the target response I can almost tell the target depth and determine how deep to place the shovel under the target. Over time, you will get very good at recovering coin targets/rings on the beach using this method. I can recover the target in 15 seconds from the time I hear the beep, most of the time.

I have a sand scoop but the beach basket is much more efficient. Try it.

Joseph Rogowski

[sinclairuser]

dave go to asda and buy a utensil strainer for 3 pounds(stainless steel), raid an old drill for a screw on handle,like this, then remove this part,just unscrew the bolt in the handle,
add a large washer inside the strainer, and insert the bolt through this washer and one of the holes in the strainer,like this, put another washer on the outside of the strainer, then screw back on the handle nice and tight, like this, and you should have this.
this is complete, you may have to buy a bolt the right thread, as some are not threaded all the way down, but it works, you can use it as a hand scoop, or put a long handle inside the drill handle to save your back, total cost 5 quid.
dont know why the last pic is the only one that worked, but you get the idea

[daverave]

do you have a photo of your beach basket ?????

[daverave]

dave go to asda and buy a utensil strainer for 3 pounds(stainless steel), raid an old drill for a screw on handle,like this[ATTACH]29813[/ATTACH], then remove this part,just unscrew the bolt in the handle[ATTACH]29814[/ATTACH],
add a large washer inside the strainer, and insert the bolt through this washer and one of the holes in the strainer,[ATTACH]29815[/ATTACH]like this, put another washer on the outside of the strainer, then screw back on the handle nice and tight,[ATTACH]29816[/ATTACH] like this, and you should have this[ATTACH]29817[/ATTACH].
this is complete[ATTACH]29818[/ATTACH], you may have to buy a bolt the right thread, as some are not threaded all the way down, but it works, you can use it as a hand scoop, or put a long handle inside the drill handle to save your back, total cost 5 quid.[ATTACH]29819[/ATTACH]
dont know why the last pic is the only one that worked, but you get the idea[ATTACH]29820[/ATTACH]

thats a very good idea but i would need a long handle as i want to use with my foot....looks good in your photo

[daverave]

hi there Joseph
do you have a photo of your beach basket ??? i still keep read your artical on fast coils...ive just ordered some teflon 28 awg 7 strand wire and hope this will be good...my first coil i just used 30 swg copper wire and i get great results so i wonder what the difference will be between the teflon and normal copper wire types.....my second coil although it works i used cat 6 wire but i used too much resin and the coil weighs in at around 2 pounds this time im hoping to use polystyrene to bulk out the coil and use small layer of resin on top and hope will be lighter and water proof !!!!

[bbsailor]

hi there Joseph
do you have a photo of your beach basket ??? i still keep read your artical on fast coils...ive just ordered some teflon 28 awg 7 strand wire and hope this will be good...my first coil i just used 30 swg copper wire and i get great results so i wonder what the difference will be between the teflon and normal copper wire types.....my second coil although it works i used cat 6 wire but i used too much resin and the coil weighs in at around 2 pounds this time im hoping to use polystyrene to bulk out the coil and use small layer of resin on top and hope will be lighter and water proof !!!!

Daverave,

I'll look for a photo of the beach basket.

On Teflon stranded wire... consider the smallest gold target you may want to detect. When your coil wire starts looking like the smallest gold target you are seeking at sub 10us time delays, the wire size can start to become an issue. I believe that you can use AWG 28 with 7 strands down to about 5 or 6 uS but beware of the size of your solder joint to the center and the shield as this solder joint blob may become a target. Use a probe to test if you can detect the wire, the coax or the solder joint beween the coil wire and the coax. It is the dielectric constant (DC) of the insulation that makes the Teflon work well. Teflon has a DC of near 2 while PVC is near 6. Lower is better as it is a better insulator and makes a coil with a higher self resonant frequency. This low coil capacitance, together with finding a way to have less coil to shield capacitance, less coax cable capacitance and less MOSFET COSS capacitance all contribute to making a coil that can be damped with a higher value damping resistor and thus have the potential to sample sooner if the PI circuit can be modified to sample sooner than the stock design. See Carl' s Hammerhead article for the changes in the resistor in the delay circuit to allow a lower delay adjustment range.

When using very fast pulses in the multi-thousand PPS range the coil wire size is typically thinner than the low PPS range (100 to 500 PPS) detectors that use a higher current pulse in the 200 uS to 300 uS TX pulse width to reach deeper targets with higher TX power.

Remember, one coil size cannot be optimal for all target types and sizes. Small gold targets like 1, to 2 mm gold chain links require a smaller coil with more turns or a probe to detect them. Coin targets, unbroken gold ring targets can be more effectively detected by using coils in the 10 inch to 15 inch range. I find that a 11 to 12 inch coil works well on the beach and can detect U.S. nickels and gold rings to about 15 inches.

Whatever wire you choose to use for your coil, just measure the coil self resonance frequency at the end of the coax when connected to the shielded coil. Higher is better.

Joseph Rogowski

[baum7154]

[QUOTE=bbsailor;190515]Daverave,

I'll look for a photo of the beach basket.

On Teflon stranded wire... consider the smallest gold target you may want to detect. When your coil wire starts looking like the smallest gold target you are seeking at sub 10us time delays, the wire size can start to become an issue. I believe that you can use AWG 28 with 7 strands down to about 5 or 6 uS but beware of the size of your solder joint to the center and the shield as this solder joint blob may become a target. Use a probe to test if you can detect the wire, the coax or the solder joint beween the coil wire and the coax. It is the dielectric constant (DC) of the insulation that makes the Teflon work well. Teflon has a DC of near 2 while PVC is near 6. Lower is better as it is a better insulator and makes a coil with a higher self resonant frequency.

--------------------

As an alternative to coax and the significant capacitance most coax contributes to slowing down a coil/feed system, you can try a 33" to 36" continuation of the coil wire twisted at a rate of about 3 turns per inch as the feedline. This twisted feedline contributes about 1pf per inch of length which is better than most coax. In addition there will be no solder joints near the coil to become a false target. I use this method and there is no performance problem with it. Metal objects held directly against this feed line are not detected.

Dan

[sinclairuser]

thats a very good idea but i would need a long handle as i want to use with my foot....looks good in your photo

the centre of the drill handle is hollow i made a strong stick that slots in, but i use it as a hand scoop most, though its plenty strong enough with the long handle.

[daverave]

[QUOTE=baum7154;190522]

Daverave,

I'll look for a photo of the beach basket.

On Teflon stranded wire... consider the smallest gold target you may want to detect. When your coil wire starts looking like the smallest gold target you are seeking at sub 10us time delays, the wire size can start to become an issue. I believe that you can use AWG 28 with 7 strands down to about 5 or 6 uS but beware of the size of your solder joint to the center and the shield as this solder joint blob may become a target. Use a probe to test if you can detect the wire, the coax or the solder joint beween the coil wire and the coax. It is the dielectric constant (DC) of the insulation that makes the Teflon work well. Teflon has a DC of near 2 while PVC is near 6. Lower is better as it is a better insulator and makes a coil with a higher self resonant frequency.

--------------------

As an alternative to coax and the significant capacitance most coax contributes to slowing down a coil/feed system, you can try a 33" to 36" continuation of the coil wire twisted at a rate of about 3 turns per inch as the feedline. This twisted feedline contributes about 1pf per inch of length which is better than most coax. In addition there will be no solder joints near the coil to become a false target. I use this method and there is no performance problem with it. Metal objects held directly against this feed line are not detected.

Dan

that is a great idea and i never thought about that before....i guess it would need some plastic sleeving over it to protect...but its worth considering doing instead of coax.

[daverave]

Daverave,

I'll look for a photo of the beach basket.

On Teflon stranded wire... consider the smallest gold target you may want to detect. When your coil wire starts looking like the smallest gold target you are seeking at sub 10us time delays, the wire size can start to become an issue. I believe that you can use AWG 28 with 7 strands down to about 5 or 6 uS but beware of the size of your solder joint to the center and the shield as this solder joint blob may become a target. Use a probe to test if you can detect the wire, the coax or the solder joint beween the coil wire and the coax. It is the dielectric constant (DC) of the insulation that makes the Teflon work well. Teflon has a DC of near 2 while PVC is near 6. Lower is better as it is a better insulator and makes a coil with a higher self resonant frequency. This low coil capacitance, together with finding a way to have less coil to shield capacitance, less coax cable capacitance and less MOSFET COSS capacitance all contribute to making a coil that can be damped with a higher value damping resistor and thus have the potential to sample sooner if the PI circuit can be modified to sample sooner than the stock design. See Carl' s Hammerhead article for the changes in the resistor in the delay circuit to allow a lower delay adjustment range.

When using very fast pulses in the multi-thousand PPS range the coil wire size is typically thinner than the low PPS range (100 to 500 PPS) detectors that use a higher current pulse in the 200 uS to 300 uS TX pulse width to reach deeper targets with higher TX power.

Remember, one coil size cannot be optimal for all target types and sizes. Small gold targets like 1, to 2 mm gold chain links require a smaller coil with more turns or a probe to detect them. Coin targets, unbroken gold ring targets can be more effectively detected by using coils in the 10 inch to 15 inch range. I find that a 11 to 12 inch coil works well on the beach and can detect U.S. nickels and gold rings to about 15 inches.

Whatever wire you choose to use for your coil, just measure the coil self resonance frequency at the end of the coax when connected to the shielded coil. Higher is better.

Joseph Rogowski

ive been reading your reply with great interest and trying to get these principles into my head....do you think its good to use a high a high pulse frequency ??? on my first detector i used 1500hz which is very good for some targets but not fantastic on like 18 & 22ct gold rings....but thin 9ct seems much better detection depth....my second detector i used 2.6khz but not as deep as my first detector but pinpointing much better....i noticed most of the commercial pulse detectors run at about 700 to 800hz and still get good depth...im a little vague about which frequency is best.

[baum7154]

[QUOTE=daverave;190575]

that is a great idea and i never thought about that before....i guess it would need some plastic sleeving over it to protect...but its worth considering doing instead of coax.

--------------------

You are absolutely right on the need for sleeving over the feed line. I use two layers of heat shrink that comes in 36" lengths. Extra sleeving is also used at the coil entrance to reinforce it and at the connector going into the detector housing.

Regards,

Dan