Ferrite antenna: Is the signal pulled in like a magnet?

[Mike(Mont)]

i don't even know how to ask this question. Is the signal there before you point the ferrite rod at it? Or is it created only after the ferrite is pointed at it? :nerd:

[Geo]

Ferrite don't create any signal.
Because too many magnetic lines are forced to go through it, we say that it is a kind of amplification.

[Mike(Mont)]

I'm not so sure about it. As I understand it, the flux lines are gathered through the ferrite. And this might create a conduit for the signal to travel along--a magnetic highway like what happens with the sun at times. I don't know but there is something going on there for sure.

I even think the human body has some sort of signal draw. It's like the lines are not there until they get developed, either from walking near the target or waving the antenna in that direction a few times like stroking a piece of iron with a magnet. Then the lines are pulled to the receiver and form the signal. Maybe.

[Mike(Mont)]

i know this probably isn't the exact same thing and a loctor works on a much lower scale, but if you've seen one of those plasma globes, when you put your finger near it the pathway forms. Probably the same process with a lightning rod. The path is created--it is not there to begin with. And OMG yes, with the "L" word L-rod.

[Mike(Mont)]

Don't know if this is any help.

www.sparkbangbuzz.com/els/magbdcst-el.htm

[Mike(Mont)]

Of course I don't know WTF I'm talking about! :help: I am just trying to think what some call "outside the box" but I prefer "outside the walls of the lab maze". When i was about four years old I loved the TV show "Mighty Mouse". My mom bought me a Mighty Mouse shirt with a cape on it. I asked her "Does this mean I can fly now?" She replied "Yes'" So I jumped off the back porch. Wow what a shock of disbelief when I hit the ground! i really thought I was going to fly.

[Mike(Mont)]

I'm sure the skeptics will say "Some things never change." :lol: Well it was 18 years later before I buitl my own hang glider and flew off the Snake River Canyon years ahead of Evel Knieval. I like one of his quotes "All the money in the world can't get you into Heaven, and it won't buy your way out of Hell..."

I'm surprised Geo is the only brave one to wade in here on this thread.

[WM6]

Don't know if this is any help.

www.sparkbangbuzz.com/els/magbdcst-el.htm (http://www.sparkbangbuzz.com/els/magbdcst-el.htm)

Interesting explanations but probably not based in existing physics.

Changeable magnetic field (as generated per detectors coils) is not the same as radio wave.
"copper wire around the house and driving it with the speaker output" does not emit radio waves, it only create changeable magnetic field (mostly inside) loop. Similar or equal as so called "ground loop" coil used in prospecting and earth survey. Neither can emit radio waves.

One simple experiment can prove us that electromagnetic field and radio waves are not the same. If you wrap your Walkie Talkie in Alu foil it can stop to emit and receive radio waves, but if you wrap detector coil (in fact most of those coil are already wrapped) in the same foil, you cannot stop magnetic field to go (out and in), through Alu foil.

Magic word here is resonance and phase. You cannot emit radio waves without resonance creating phase between radio wave components, on other side, detectors changeable magnetic field emitting and receiving coils in general does not need (PI coil par example) any resonance to emit EM field and by following phase we can only distinguish metal parts instead of propgate. There are exception (Enigma p.e.). And some detectors design are based on radio waves instead of changeable magnetic field (GPR devices, some mine detectors..).

But radio waves are composed from magnetic component too. This why ferrite antenna works. As Geo explain it aspirate nearby magnetic (as all ferromagnetic in general) field lines and this way strengthen radio signal at given location:

http://www.radio-electronics.com/images/ferrite-rod-antenna-operation.gif

More reading:

http://physics.stackexchange.com/questions/181277/do-the-electric-and-magnetic-components-of-an-electromagnetic-wave-really-genera

[Mike(Mont)]

I need to find some info on the solar magnetic highway to explain this better. Kinda wish i hadn't posted that sparkbangbuzz link. Not quite what I am referring to.

[Mike(Mont)]

maybe I'm so far out there no one understands what I am asking. :shrug:

[WM6]

maybe I'm so far out there no one understands what I am asking. :shrug:

Do you understand what you asked?

" Is the signal there before you point the ferrite rod at it? Or is it created only after the ferrite is pointed at it? :nerd:"

Geo already answered your question.

Without signal already existing, there is no job for ferrite antenna. It only concentrate existing signal to get more flux through coil wound on ferrite. Ferrite antenna cannot create signal out of nothing. RA signals are not stationary they are traveling from its source to endless in concentric signal stream.

Ferrite antenna act like hopper in water stream, it caught and concentrate stream from wide to tight opening and give him more pressure at narrow side (this way we get stream gain = related to signal gain in ferrite antenna).

[Mike(Mont)]

Okay i get confused some times. Maybe i was thinking about a loop antenna but they both do basically the same thing. I don't claim to be no electronics nut, but the way i understand it, I hold the ferrite so the broad side is facing the target. Or with a loop antenna so the windings are pointed at the target. Not the same system as a pistor detector. The magnetic component hits the front side first. But whatever the case, I still hold that there is some kind of magnetic pathway that forms. That's my story and I'm sticking to it. LOL

[WM6]

If target act as radio wave source (in case of reflected radio waves - from using GPR apparatus par example or distance radio station using Gold Gun pistol), ferrite antenna can point to those targets: if from target surface reflected signal is strong enough and suit to radio band to which ferrite antenna is tuned. But, this (reflection from targets) is all in case, if we hunt using radio waves (which incorporate magnetic component too).

When we hunt using changeable magnetic field (as with most metal detectors), there is no reflection of magnetic field from targets surface. Targets in changeable magnetic fields act as many very small oscillatory circuits (as many such minuscule circuits, as many eddy currents was created at target surface) and in consequence metal targets act in changeable magnetic field as load (by changing inductance of coil, frequency of coil tank circuit, or amplitude and phase of oscillation).

Where we have magnetic component: as main one (in case of metal detector) or as part of radiation (in case of radio waves), we can use ferrite antenna: as to wave source pointing direction or as magnetic field concentrating means (two such examples: transistor SW radio, pinpointer).

[Mike(Mont)]

If the ferrite rod nulls (goes quiet) when the end is pointed at the target, is that magnetic?

[WM6]

Of course all is about magnetic influence of changeable magnetic field.

But, nulling existing signal pointed ferrite antenna at its source, is not due ferrite, it is due electronic circuit design after ferrite antenna. It can be unintentionally bad (saturation of first stage at some input signal level) or intentionally good, depend of our expected achievement.

Nulling of existing signal can be made due receiving reflected signal in counter phase too (as pa example tin hut somewhere behind you).

[Mike(Mont)]

I'm still vague on all of this. I thought the Gold Gun uses the null to locate the target.

Since I'm on this, what is the advantage of using a long thin ferrite rod versus a shorter, fatter one? Is it just a cost (save money) issue?

[WM6]

Depend on its circuit building and tunning, GG circuit can detect by nulling signal too. Not sure how original one work, I haven't one.

With longer thin ferrite rod you get more directive antenna to more precisely point at target location, with shorter and fatter one you get more sensitive (more gain) antenna to sense weaker signals.

[Mike(Mont)]

Depend on its circuit building and tunning, GG circuit can detect by nulling signal too. Not sure how original one work, I haven't one.

With longer thin ferrite rod you get more directive antenna to more precisely point at target location, with shorter and fatter one you get more sensitive (more gain) antenna to sense weaker signals.

Okay, thanks for that. I feel like the short, fat one gives cleaner signal but sensitive to direction. The thin one seems noisy but it's a lower permeability.

Pretty sure the Gold Gun and AGR receiver use the null to locate the target by pointing the end of the ferrite rod at the target. They look for a drop in the signal or whatever it is, background noise?

[WM6]

It is always problem how to distinguish between useful signal and all sort of environmental interference signal (including useful signal unwanted reflexed from objects around our location).

The only primitive (conditionally) solution is to build extremely directive antenna that can receive (practically) in pointed direction only and by this suppress all other sources of signals. Or we need to go more sophisticated and expensive way to digital filtering and selecting useful signal out of signals cacophony.

[WM6]

Okay, thanks for that. I feel like the short, fat one gives cleaner signal but sensitive to direction. The thin one seems noisy but it's a lower permeability.



Solutions to more directive antennas are known.

We need to use two or more antennas (instead one only) in parallel, at given distance between them and follow phase of each one to get equal balance (which mean "null" direction). Unfortunately, to get practically applicable device, we are here limited to suitable wavelength (shorter wavelength mean more useful/practical construction of our device).

GG follow such directivity idea, but with "in-line" design of two ferrite antenas instead of two parallel placed at adequate distance. Such "in-line" tuning could be more critical.

[Mike(Mont)]

Okay, I didn't see the GG that the two ferrite rods run to separate circuits. AGR Receiver probably the same.

[Mike(Mont)]

Okay, thanks for that. I feel like the short, fat one gives cleaner signal but sensitive to direction. The thin one seems noisy but it's a lower permeability.

Pretty sure the Gold Gun and AGR receiver use the null to locate the target by pointing the end of the ferrite rod at the target. They look for a drop in the signal or whatever it is, background noise?

When i say the short ferrite rod is "sensitive to direction" I mean it is like aiming a pistol compared to a long barrel rifle, it's harder to aim. Definitely not the same as the long thin rod. I need more time with it, just got it wound last night. But so far I like it better.

[taxma1981]

with small ferrite i have gut signal:)

[WM6]

Okay, I didn't see the GG that the two ferrite rods run to separate circuits. AGR Receiver probably the same.

Your do not need separate circuits, only separate antennas driven by same circuit. Something like Dual or Quad Yagi antenna. GG is pure VLF radio device with two separate antennas proper mutual equilibrated.


with small ferrite i have gut signal:)

No doubt. With short fat ferrite antenna you receive a lot more different signals, than with long directive antenna. Question is what use of all those "gut signals". Did you take a look at spectrum of all those signals in spectrum analyzer? Try and you will see what a mess you receive.

[taxma1981]

6 vlf station:χαχαχα:
http://s30.postimg.org/7plga1jb1/20160104_223805.jpg (http://postimg.org/image/7plga1jb1/)

[taxma1981]

and one example with not ferrite antenna,box 1 with gold and silver,box 2 with paper:lol:
http://s10.postimg.org/asfnj98lx/Specgraphghhkkooohhz.jpg (http://postimg.org/image/asfnj98lx/)http://s27.postimg.org/yonr2tjun/20160107_000331.jpg (http://postimg.org/image/yonr2tjun/)

[taxma1981]

i use gold gun with fm transmitter and receiver
http://s29.postimg.org/3satjgw2r/WIN_20160105_212722.jpg (http://postimg.org/image/3satjgw2r/)

[Mike(Mont)]

I guess it depends on the receiver, but that's just a guess why it works better. At least it appears so with my test targets. I know you won't be happy with this answer, but...That's my story and I'm sticking to it.:)

[WM6]

No doubt, receiver is important, but don't forget: antenna is always part of receiver.

[taxma1981]

The antenna make the diference

[WM6]

Exactly, but it not easy task to make HiQ antenna.

[Mike(Mont)]

yeah, the loop antenna is more powerful than the ferrite antenna. The gain on the receiver has to be lowered. It requires a few minutes between practice rounds otherwise it will detect where the target was on the last round. The ferrite rod usually does not pick up the residual nearly so much if at all. At least that is with a half ounce of silver.

[taxma1981]

I have this antenna and it is better from ferrite antenna :)
http://s8.postimg.org/ygnfq63n5/20160107_191745.jpg (http://postimg.org/image/ygnfq63n5/)

[abdou2014]

HELLO. GOOD WORK . PLEASE DIAMETER OF WIRE AND NUMBER OF TOUR. I WANT TRY IT

[Mike(Mont)]

I have this antenna and it is better from ferrite antenna :)
http://s8.postimg.org/ygnfq63n5/20160107_191745.jpg (http://postimg.org/image/ygnfq63n5/)

Yes, I like the idea...I will build one.

[taxma1981]

The coils haven 10 cm diameter,

Wire 0.2 mm

9-10 mh

[Mike(Mont)]

Is that for transmit?

[taxma1981]

This is the coil from receiver

[abdou2014]

10 Mh is too much . what is the value of parallel capacitor

[taxma1981]

10 Mh is too much . what is the value of parallel capacitor


820pf


mh not Mh

[abdou2014]

10 millihenry is too much . what is your reception range .

[taxma1981]

theoretically 58-60 khz :χαχαχα:

One example
https://youtu.be/SXeBqkunHbk

[abdou2014]

you must calibre it with transmitter . my GG918 work between 35-80 Khz.

http://www.longrangelocators.com/forums/showthread.php?t=15058&page=6

58-60 Khz it's not enough .

[taxma1981]

58-60 khz with this antenna and 10-24 with second antenna:D

[taxma1981]

you must calibre it with transmitter . my GG918 work between 35-80 Khz.

http://www.longrangelocators.com/forums/showthread.php?t=15058&page=6

58-60 Khz it's not enough .

do you have video??

[abdou2014]

i did not now. but i'll do one next time .did you find anything with it

[taxma1981]

i dont test it:)

[abdou2014]

you must test it and find gold with it . That's the real success !!!

[Mike(Mont)]

Found out today the threshold was set too tight. By giving a little more room before it goes off, there are less weak, broken signals, gets rid of the scattered garbage. Easier and more accurate to pinpoint this way. Less false alarms. I always thought the threshold had to be so close, so tight like with a metal detector, but not the case. Sort of like the squelch on a CB radio if it sounds off too easily you just get a lot of static. Works much better now. :)

[Mike(Mont)]

Been working indoors today due to cold weather. The loop antenna is just not as accurate indoors. Need to redesign it, I guess. I have found that the wire position is critical. Just a few wraps out of place (off center) and there is a very noticeable effect--it does not aim correctly.

user.netonecom.net/~swordman/Radio/re-loop-article.htm

You see why i hate posting links. That's the right address, you'll just have to copy it yourself or search "Doug's loop antenna article"

[Mike(Mont)]

Just a note most people probably already know--keep you hands away from the ferrite rod.

[Mike(Mont)]

I tried to rewire the loop antenna. It was better before I messed with it. Now it gives a wide response instead of a sharp, narrow one. So back to the drawing board. But I am leaning more towards the fat, short ferrite rod again. The loop is just too sensitive and touchy, and somewhat delicate (if the windings get moved out of place).

[Mike(Mont)]

When I get my hand near the unshielded ferrite rod, it starts to squawk and squeal, hiss, crackled, spit and sputter, and a few others. I tried insulating it but that had no effect. From eight inches (20cm) I don't hear any of this and it seems to work fine. Haven't tried to shield this one, but I suspect it might help some as the shielded loop does not exhibit the interference nearly as much. I just wonder with the pistol detectors how much this is a problem because the hand is near to the ferrite rod.

[Mike(Mont)]

That thin ferrite rod is disgustingly fragile. :frown: I can't see using that on a pistol detector--just tap the case with your finger and you risk breaking it.

[Mike(Mont)]

What difference does a longer ferrite rod make? Does it change inductance?

[Geo]

No.
If you use it at input of a tuned circuit of a receiver then has the ability to catch smaller signals or to become more directional.

[Mike(Mont)]

Okay, thanks Geo. Looking at those plastic coated rods at Stormwise.com