IDX-PRO+VDI

[Koala]

I made (not for IDX, but for IGSL musketeer, should be very similar in behavior) classic 27cm and 33cm DD and CC with diameters Tx 25cm Rx 8cm (I wanted good separator and pinpointer so I made Rx much smaller than half). I have very old field next to my house, full of rusty nails. 33cm DD was unusable, only detects bigger irons. 27cm DD was bit better, but localization of colored targets was pain in the ***. Only coil, which I was able to finaly dig something with, was that small CC. I love it, when it comes to old houses. CC has bigger problems with hot rocks compared to DDs, but around old houses or dumps its unbeatable. Pinpointing is like laser, definitely will make few more and try them on higher frequencies (than actual 8kHz), because even now (and none of my other coils is able to) it detects smallest golden chains I borrowed from my wife...

I built a 5.75" concentric for my Bandido. Surprised just how deep it was on are hammered coins we have here in the UK. Depth is the same as larger coils up to our pre decimal coppers. Theres only so many corroded copper coins I can collect.


Best of all even coins on edge are within a 3" square making recovery very fast. You do pick up more .22 cases and shotgun pellets.

[Hyena]

That's an interesting thought.

I have built both concentric and DD and the best separation on a large lump of iron and a small silver is always the coil radius. I thought the DD would have been better. But in testing they were the same. That's with the RX half the TX size.

Coins on edge on s concentric beep when the RX is over the coin. I suspect it would be the same with a larger RX pushing it towards the heel and toe of the coil making pinpointing worse

I made (not for IDX, but for IGSL musketeer, should be very similar in behavior) classic 27cm and 33cm DD and CC with diameters Tx 25cm Rx 8cm (I wanted good separator and pinpointer so I made Rx much smaller than half). I have very old field next to my house, full of rusty nails. 33cm DD was unusable, only detects bigger irons. 27cm DD was bit better, but localization of colored targets was pain in the ***. Only coil, which I was able to finaly dig something with, was that small CC. I love it, when it comes to old houses. CC has bigger problems with hot rocks compared to DDs, but around old houses or dumps its unbeatable. Pinpointing is like laser, definitely will make few more and try them on higher frequencies (than actual 8kHz), because even now (and none of my other coils is able to) it detects smallest golden chains I borrowed from my wife...

[Koala]

But... wil it have the same separation capabilities like CC with smaller Rx have? Will it have the same problems with hot rocks? I would rather go for DD then.

That's an interesting thought.

I have built both concentric and DD and the best separation on a large lump of iron and a small silver is always the coil radius. I thought the DD would have been better. But in testing they were the same. That's with the RX half the TX size.

Coins on edge on s concentric beep when the RX is over the coin. I suspect it would be the same with a larger RX pushing it towards the heel and toe of the coil making pinpointing worse

[Hyena]

But... wil it have the same separation capabilities like CC with smaller Rx have? Will it have the same problems with hot rocks? I would rather go for DD then.

[Qiaozhi]

I often wondered about placing Rx on outside of tx as seen on a few coplanar coil designs or making Rx larger with respect to tx.This certainly wouldn't require hundreds of turns.

In Chapter 10 of ITMD (pages 128 and 129), Experiment #4 used a Troy 9" concentric coil with the Raptor Project. Due to the coil inductances being unsuitable for use with the transmit ccircuit, the inner coil was used as the TX, and the outer coil was use as the RX. Surprisingly this configuration worked reasonably well.

[wallker]

I used .15.

don't think it matters too much but makes a small bundle when doing 270 turns.

Tnx Koala.

That's also why I stay away from concentric, the Rx requires too many turns, wire not exactly cheap. I often wondered about placing Rx on outside of tx as seen on a few coplanar coil designs or making Rx larger with respect to tx.This certainly wouldn't require hundreds of turns.
If you have unlimited supply of wire, then number of turns is not an issue. You can build any number of coils of various sizes.

Wire isn't problem for me, but idea about placing rx on outside of tx sounds interesting.

[dbanner]

That's also why I stay away from concentric, the Rx requires too many turns, wire not exactly cheap. I often wondered about placing Rx on outside of tx as seen on a few coplanar coil designs or making Rx larger with respect to tx.This certainly wouldn't require hundreds of turns.
If you have unlimited supply of wire, then number of turns is not an issue. You can build any number of coils of various sizes.

[Koala]

Thanks for the tip about concentric, but i got quite nice setup for winding 27 cm DD, so for now i will make this one.
Latter may try with DOD or concentric.
Which wire for rx of DD 27 cm is better: 0,15 ; 0,16 or 0,18?
Have them all three laying around.

I used .15.

don't think it matters too much but makes a small bundle when doing 270 turns.

[wallker]

Performance would be similar to concentric coplanar coil.
Problem here is the difficulty with estimation of number of turns for the tx. Trial and error and some rough calculations got me close enough to required inductance. But I abandoned making these coils because I haven't been able to make easy calculations for inductances with the squiggle( omega) design. And it's a pain to bend the coil into its place without dedicated omega housing with grooves.

Exactly why i don't give it a try making it.

[wallker]

Thanks for the tip about concentric, but i got quite nice setup for winding 27 cm DD, so for now i will make this one.
Latter may try with DOD or concentric.
Which wire for rx of DD 27 cm is better: 0,15 ; 0,16 or 0,18?
Have them all three laying around.

[dbanner]

Nope you would be the first to try

the inductance and capacitors would be the same as per first page of this thread.

RX is half the diameter of the TX


just don't know how to calculate the size of the squiggle so the RX is near the centre. Looks to me to be a fraction below RX size

The squiggle varies by manufacturer of old style omega coils according to size ratio of Rx coil.
I built omega coil based on exact dimensions of Heathkit omega coil photograph which I traced out on paper. I then put a string along edge of the tx and squiggle to get the total circumference. Then I calculated radius of circle with same circumference and wound tx coil. The trick was to get the number of turns correct. It was easy to balance using slides on Rx coil as shown on Heathkit coil
photo. You can make any size coil just using same proportions, simply by printing larger image of photo.
It balanced such that the Rx was very close to the center. This happens always when using the Heathkit omega coil proportions. The Rx balances close to the geometric centre of the search head, which is the more preferred outcome for pinpointing.
Performance would be similar to concentric coplanar coil.
Problem here is the difficulty with estimation of number of turns for the tx. Trial and error and some rough calculations got me close enough to required inductance. But I abandoned making these coils because I haven't been able to make easy calculations for inductances with the squiggle( omega) design. And it's a pain to bend the coil into its place without dedicated omega housing with grooves.

[Koala]

I built a few coil for the IDX Including 10" and 12" DD.

By far the most used coil was a 8" concentric in the fields near me. 12" DD out preformed it on a coin in my lawn. However when searching in fields you would have to turn the discrimination up and you lose all sensitivity to small thin items on edge

Never got round to building a 10" concentric. Fairly sure that would have made my other coils redundant.

if I was going to build a coil which I was sure to work 100% then I would follow this https://www.geotech1.com/forums/show...idx+concentric

of cause in your fields things might be different. For example dry sand without much iron the 12" DD would have been my choice just because of the better coverage

[wallker]

I googled a bit, and there is just not enough data for omega coils...

For now i will make DD, afterwards may try super D or as some call them DOD.
Did anyone tried DOD on IDX, how does it performs?
Should be better than DD?

[Koala]

Hi Koala, fo you have some parameters for omega coil?

I might give a try building it.

Nope you would be the first to try

the inductance and capacitors would be the same as per first page of this thread.

RX is half the diameter of the TX


just don't know how to calculate the size of the squiggle so the RX is near the centre. Looks to me to be a fraction below RX size

[wallker]

Hi Koala, fo you have some parameters for omega coil?

I might give a try building it.