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Offline mykaitchTopic starter
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« on: January 13, 2013, 07:33:23 am »
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In my earlier posts I urged against wrapping coils in tape. There was a good reason for this; as the coil is compressed by the tape the air gap in the turns (that is difficult to avoid) closes and the inductance increases. BUT, I missed a point. I see that all DIY methods involve applying some kind of glue which will help hold the coil rigid and will close the air gap or keep it constant (I guess). After applying three coats of varnish to mine I was able to tune the frequency exactly, I then used the tape but although it is well wrapped, I took care not to pull the tape so tight that it amalgamted (some tapes are intended to do this), and the tuning did not change.
I have a pic of a coil on another computer (will post it later) which is a commercial product from a commercial detector: it has no tape at all, just spiral wrap (good idea), looks like the same wire I use (Kewsol) and is not set in any kind of resin. Again, I guess for underwater work you may need the resin ? I am assuming too that making the coils very accurately will result in a better head. The info I have insists that the Tx coil tunes at 10Khz and the Rx coil at 10.5 KHz - I read on the GeoTech board that it is desirable for the Rx coil to be slightly off tune. Why is this ? Does it help with the phase detector ?

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Offline GoldDigger1950
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« Reply #1 on: January 13, 2013, 08:03:13 am »
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Quote:Posted by mykaitch
I read on the GeoTech board that it is desirable for the Rx coil to be slightly off tune. Why is this ? Does it help with the phase detector ?

That's exactly backwards. The TX coil won't radiate at all if it is in a tuned circuit. Did you not read my replies to you earlier? I'm guessing you simply brushed them off because I disagreed with you. That's a real pity since I have more than 40 years experience in design electronics with a few patents still in use today by manufacturers. Your choice. Read and heed an engineer's words or read and heed a novice DIY type.

And now you are back here, defending your "don't use tape" theory with a story that defies sense. First you say you can't use tape and now you tell us you DID use tape. Which is it?

The air between the coils is not the issue at all. It is the distance between the wires. Wrapping the wires keeps the wires from moving about causing shifts due to bumping and other movements. The tape and the potting keep the coil from moving. Once you get the right formula for turns, wrapping and so forth, the coil being taped is a benefit. Please refrain from implying that I am incorrect even if you truly believe it. You are giving people here bad advice. You need to stop it and do that now, please. Tape is not the enemy nor is air. Keeping the wire from moving is the essential job they do.

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« Last Edit: January 13, 2013, 08:09:02 am by GoldDigger1950 »
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Offline mykaitchTopic starter
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« Reply #2 on: January 13, 2013, 12:45:05 pm »
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I don't want a flame war. I have said that you are  right  re reactance and the use of tape. I have now used tape with no problem after heeding your advice. I have had almost 50years,7 patents etc. Whoopee. I still make mistakes. We never stop learning.
Now, if you wind a coil loosely it will be very different to one wound tightly - certainly in my more familiar area of 1GHz and anyway the principle is true as shown by the coils I have wound. I have also accepted that the coil must be stable.

' The TX coil won't radiate at all if it is in a tuned circuit.', I see, you mean the osc will run at the right f regardless of the inductance, fascinating. Funny
'
And now you are back here, defending your "don't use tape" theory with a story that defies sense.' NO.Iam saying you are right, sensei.
 
'The air between the coils is not the issue at all. It is the distance between the wire'. Excuse me ? What is in the  gap between the wires? I thought it was air.

 I read on the GeoTech board that it is desirable for the Rx coil to be slightly off tune. Why is this ? Does it help with the phase detector ?

Stop all this silliness. I think it is a language problem. Kiss

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Offline GoldDigger1950
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« Reply #3 on: January 13, 2013, 02:30:53 pm »
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Quote:Posted by mykaitch
I don't want a flame war. I have said that you are  right

No you didn't. You said you had a good reason for saying to continue not to use tape. Just remember one thing. There is no such thing as a flame war with a moderator on a forum. The next peep out of you sees you muted and the flaming ends there. Period.

Posted on: January 13, 2013, 10:25:27 PM
Quote:Posted by mykaitch
The TX coil won't radiate at all if it is in a tuned circuit.', I see, you mean the osc will run at the right f regardless of the inductance, fascinating.

No. What I mean is that energy in a tuned circuit stays 100% inside of that tuned circuit. Imperfections in the coil allow a tiny bit of field but to get a really big field, which is desired, you must detune the TX coile by 6db down. The receiver must be tuned to that frequency exactly to get maximum field detection of eddy currents. Remember, you are not receiving the actual TX signal. You are detecting surface and interior eddy currents in targets.

Posted on: January 13, 2013, 10:28:10 PM
Quote:Posted by mykaitch
Stop all this silliness. I think it is a language problem.

I speak English. Perhaps even better than you. I'm a published writer in another field with a few articles on treasure hunting. As to stopping the silliness, try paying attention. Did you go back and read my post and reply to you that explained all of what I just wrote again here? Probably not. Too busy feeling like you have been "wronged" by me. I've helped dozens of people with their projects here and if you ask nicely the first time you get into a sticky spot, I'll probably help you despite your penchant for arguing here.

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Offline mykaitchTopic starter
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« Reply #4 on: January 13, 2013, 02:32:29 pm »
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The next peep out of you sees you muted and the flaming ends there. Period.
Fair enough.Typical Yank - if only the Mayflower had sunk.
Only one thing to say really


FUCK OFF YANK

(meet me on Geo Tech) Waveing

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Offline GoldDigger1950
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« Reply #5 on: January 13, 2013, 02:42:29 pm »
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Quote:Posted by mykaitch
Excuse me ? What is in the  gap between the wires? I thought it was air.

It can be air but it is often a sealant. If you leave it without any tape or other material to hold it, the coil will expand and contract with the current applied and eventually be out of tune. That's a fact. So, leaving it without tape or potting compound is asking for a mechanical failure that cannot be repaired later. Your vision of what is going on is just a little incorrect. You have the right idea but the air is not the problem.

THE WIRE MOVING IS THE PROBLEM.

The wire needs to be stabilized completely. Most people do it with tape or string. The air between the wires is not the problem. The movement of the wire is.

Posted on: January 13, 2013, 10:34:53 PM
Quote:Posted by mykaitch
Fair enough.Typical Yank - if only the Mayflower had sunk.
Only one thing to say really


FUCK OFF YANK

(meet me on Geo Tech)

I'll let this one slide, mate. Believe me, you will run into the same issues on Geotech if you argue with the engineers over there. They're not as tolerant as we are here.

But don't go away. Give it some more time and go read what I told you in your other coil topic. Seriously. Just go read it and if you want to, I will just delete these last two posts. That's as fair as I can be.

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« Reply #6 on: January 13, 2013, 03:58:04 pm »
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WoW!     You All would be speaking German if the Mayflower sunk.    LOL

If your coil changes after Wrapping, you just have to wind them different.

If you know it's going to Go Up in uH then just wind them low and let them go up!

Was that so hard?



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« Last Edit: January 13, 2013, 05:03:03 pm by homefire »
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Offline GoldDigger1950
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« Reply #7 on: January 13, 2013, 04:52:53 pm »
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Quote:Posted by homefire
If your coil changes after Wrapping, you just have to wind them different.

Precisely.

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