Guys a little knowledge pleasey!

[qute1]

i have managed to get some cat6 plenum (teflon) cable spent the morning removing core and sheath and now have 17meters four pairs separated.
Now the sticky bit i have begun untwisting one set of pairs (i don't have space to use a drill to do it) and it looks like the christchild will put in an appearance before i finish just one set (so hot here i think i may have gone into the future anyway dripping like a knackered fridge ) .

So my question would it be wise to make a coil using the twisted pairs? pair ends soldered together (larger thick coil but hey) and if so would the resistance or inter-capacitance be too far off to upset an otherwise decent fast coil.
And will i have to adjust my turns by much to make up for inductance changes.
hope you Gurus can help me any thought gratefully received.

[waltr]

Used a pair as a single conductor, ends soldered together, would decrease to resistance and not effect inductance. This might increase inter-capacitance a little but that depends more on how the whole coil is wound.

What type of detector is this for?
PI MD coil inductance is not critical, typically 300 to 400 uH.
VLF MD's is more critical since the coil-cap most be close to the desired resonant frequency.

[qute1]

Thanks for the confirmation logic says that would be the case but sometimes logic wanders off when we start talking md's and yes pi md and aiming for 330uh ish would be much easier if i don't have to separate.

[nonkapo]

Muahahah, my dear, i'm so happy i'm not the only one suffering:-))))) I've just done it the day before - same setup. Unfortunatelly when i first do the twisted pair coil i did not write up the results, otherwise i was to be able and give you some expected figures. I manage to untwist one pair and it is not so bad(my lenght is half yours:-). It takes alot of time and patiense but i manage in around two hours. It is tricky as the cable tends to make small loops. So i end up with three different types of coil. One is the basket type made straith from UTP without unwinding(http://www.metdet.ru/korsina2.htm). Second one done with twisted pair which i'm about to make again and third from single core of UTP. The first and last one are still in tact so in the next post i will give you the details - hopefully it helps you. I make apart one more cable but surprisingly that comes with 4 pair stranded cores instead of single. It was marked as awg23, but the results of that are disapointing as the resistance come four times bigger(?!?!?) Not very logical isnt it considering should be ticker? Probably another chinese counterfeit cable...

[nonkapo]

UTP basket coil details - int. diameter - 17cm, 24AWG UTP cat.5e - R-1,6 Ohm, L - 0,36mH;
UTP single core details - int. diameter - 18cm, 24AWG UTP cat.5e - R-1,3 Ohm, L - 0.31mH
Have a look at the pictures.
Happy hunting

[qute1]

nice job nonkapo i too have tried with heavily shielded cat6e (4 pairs heavy foil sheild on each pair) and found that using the join up series method i need 6 turns on 9" (23cm) to get 350uh and resistance was high at 1.68ohm which is why i posted the thread to see if the the new cat6 plenum would be better.
It is! i went with using pairs still twisted and comes out at 20 turns 289uh (just short of the calculated but useable, next time i will use 22 turns and should be right in the ball park at 350uh) the twisted pair do have a useful feature though as only .67 ohms (nice).

[nonkapo]

Thanks for the info. How do you use the shielded one? For the basket one it should be not shielded. This paralel mode for resistance reduction i get from the spiral coil for the surf PI. Which detector you are using?

[qute1]

The shielded one is just bundle wound six turns, works but nothing to write home about, so now using that cable for box to head connection.
i have many detectors sniffer, surfpi x 2, surfpro, impulse2 x5 (testbeds), chance, felezjoo, minipulse, jabel j297 x2 and several other experimental and prototype pi's also have many brandeds vallon garrets vlf ulf etc
These coils are for the pi's playing with speed and disc though not necessarily depth as they all go deep anyhow (maybe too much as i am getting too old for 2 foot holes)

[nonkapo]

LoL come here in the desert it is much easier to dig. However when you dig the sand tend to fill up the hole again;-)(no perfect happyness).
Nice bunch of equipment you have. I'm having few on the bench(Surf, Bara, Delta pulse), however not too much time to experiment. Only in the days off.
I come to the point using the UTP as it is the only free option i have at the moment. Planing to get wider diameter UTP basket as the next target is a watch lost in area full of soft drinks can and buble gum foil junk. My Bounty hunter keeps picking it up even the smallest pieces(dont know wheter is PI or VLF).

[qute1]

I too am now restricted to days off (down side to a very welcome job) my main driver for the experimentals is the need to discern alloys from silver/gold whilst completely ignoring ferrous (suspect watch internals are non magnetic stainless steel so might be ok for your project) ground here is very hard (specially at the mo too hot and dry like concrete) even after autumn rains and full of dead tractor parts.

[nonkapo]

Started spider web coil with the same twisted pair. Let's see what will come out. It is such I pain in the a.. though I'm giving up for today. Tomorrow hopefully will share the result.

[qute1]

Your empirical results are awaited eagerly!

[nonkapo]

I can highly recommend it to you now. So far the best dept i get in the air on my Surf PI. However you will have to calculate your self some stuff. I spend the last night building it but i manage only today around 11:00. Thrust me it is a real nightmare, but i'm happy with the results. Despite that i miscalculate it (i run around 140uH and half Ohm resistance) this is so far the best coil i build. It will need alot of refinement and recalculation but the begining is promising. Keep in mind that i do not even damp it. More solid base will be required, however the current Coroplast ring does the job. It is strong enough and very light. Tha bad thing about, when making the holes for the winding it is very hard to keep them aligned, especially when the drillbit coincide with the ribs.
This is all so far, lets keep more working than posting and when i've got the final results i will share here. Photos if i manage will come soon.
Happy hunting

[qute1]

Thanks nonkapo i will try some more this afternoon (day off) aiming for 350uh.

[nonkapo]

I'm going on duty and on the way back will try to source ticker Coroplast sheet as mine was from used box - already bent here and there. I have around 20 turns so probably if you use same tickness UTP(twisted pair awg24), you should target for 30turns or above.when i connect only one of the pairs as stated before i only get increament of the resistance. However, better try the calculators(i'm not so familiar with).
- The coil
- Single wire
- Double wire

Note i try also in series and get 2,6 Ohm 560uH, also single wire with the second wire connected in circle - almost same resistance(1.3 Ohm) and only 10uH induction.