Nautilus revisited

[dbanner]

Yes, those are the coupling caps to the gate inputs, don't know the value.

[kt315]

why you do schematic from zero? first sch file has all reference designators. just to add some differences.

[dbanner]

why you do schematic from zero? first sch file has all reference designators. just to add some differences.

I don't know why. That's just how I did it. So I could start from beginning to name every component on pcb to match names on schematic. Component by component, none will be missed, all will be done thoroughly.

[dbanner]

Look for something on coils for me. The parameters, number of turns etc. Cannot find anywhere.
You have document named #schematic 2 on your hard drive of all W.lhar schemas. Look at " beach detector" based on whites CM5. Look there at coil and nulling circuit.

[Melbeta]

Dbanner
I have now found the quote in a Nautilus forum, where Brian (UK) mentioned what he felt the coil windings were. I was in error in memory, he said TriAxial Concentric, not Co-axial Concentric. However right below his posting, another fellow in Europe, had an open Nautilus coil, and he felt Brian (UK) was in error. So here are the two postings.
Melbeta
Next time you speak to him mention that the coils are triaxle concentrics with the supplied ones being "high Q" and it was Jerry Tyndall who came up with the DMC design and built the business to the stage of the machine being the number one choice for many relic and coin hunters so that the company was able to win the G.N.R.S. year after year. Credit where credit is due. UK Brian

Just out of interest what is meant by triaxle concentric? The reason I ask is that I have a broken coil that has been opened up and it looks like a regular concentric; 1 coil running around the edge and smaller one in the middle. NautiEurope

[waltr]

I have a feeling that the terminology is used 'loosely'.
Sound like this is simply a concentric coil: other TX winding, Inner RX + Buck winding. Then with a little extra loop of the Buck winding to fine tune the Null.
Since there are three coils maybe that's where the term "triaxle' (should be tri-axial) come from.

So I think the coil is build like these:
https://sites.google.com/site/dbcoil...ncentric-coils

I have build a coil for my HH2 PI detector just like this (but 400uH). That little extra wire from the Buck coil fine adjusts the null.
I have also found that in the field it will false if bumped a little too hard due to the extra wire loop being just taped into position.
I like this coil, can run sampling delay down to 12usec and it pin-points well.

[dbanner]

Waltr, thanks for that info, the 2b coil looks like standard concentric coil, but the bucking coil is supposed to be in series with Tx coil. I can't see any evidence of wire connected to tx wires that would form the bucking coil, the tx wires go straight from the tx coil and terminates at the small pcb. No other wires are connected to it. Just because I don't see it doesn't mean that they aren't there.

[dbanner]

This is not a big problem though, a standard concentric will work good. A center tap tx coil with bucking coil in series, no problem for me. Even a double D will work good.

[Melbeta]

This is not a big problem though, a standard concentric will work good. A center tap tx coil with bucking coil in series, no problem for me. Even a double D will work good.

On the DD coil, there was a post where it stated that with the DMC 2B design, a DD coil will not work, unless you change something in the design. I do not know what that change would be, just letting you know it was posted to that effect. I put a copy of the post regarding the DD coil so you can read it and then figure out what must be done for a DD coil to work.
Melbeta

DD Coils Question:
OK, Went there today . I talked with them about the DD coils. From what he said, they at one time made a unit that could use a DD coil but no longer do . I think it was the DMC1.

As for the units that they build now , these units will not work with a DD coil. They would have to redesign the front end if I remember correctly . The units that they build now are built for Depth and sensitivity. The DD coil reduces the depth and the sensitivity so that is why they do not build them.

[dbanner]

Thanks for that info, yes I also read this on Nautilus forum. Just gathering parts for construction of the electronics.
I'll have to ponder on the coil details at some later stage. I don't think it's a game stopper though.

[dbanner]

I have just been able to take a closer look at the coil photos, it is definitely just an ordinary concentric coil. I can see the busking coil wire connected in series with the tx coil, the other end of bucking coil goes to ground. Simple actually. Nothing exotic about this coil. The bucking coil turns would be in opposite direction to the tx turns, that is all. The actual number of turns can be worked out easily for a standard concentric coil type. The Rx would be made with a thinner gauge wire as is typical for concentric coils.
If I end up making this device work from just a bunch of crap photos, that would be something.
Some of the photos were good enough though.

[dbanner]

Project abandoned due to excessive price of high quality multi-turn pots.

[Skippy]

The two pots for coil-nulling 'R' and 'C' are completely unnecessary, if you null the coil properly initially. So that's two less fancy pots.
The 'Power' control pot is not necessary either, a switch for 'High' and 'Normal' is perfectly adequate.

[Gwil]

The coil nulling pots might be useful in a detector that only responded to signal amplitude, as shown in US patent 4099116 (see the Patents section of this website) but would do nothing for a detector using synchronous demodulation which ignores small constant unbalanced signals. I reckon.

[Skippy]

As the coils have a well-known tendency to drift, likely due to thermal effects, I suspect the coil tuning pots are to help overcome this trait. They would also be useful if you had additional coils, which could have different nulls and different long-term drift behaviour.

I can think of a reason for creating an imperfect null, but I don't imagine the Nauti does this.