Is there a solution to this?

[Funfinder]

If the MD coil wouldn't radiate upwards too the whole power could be doubled.

Reflector would reduce sensitivity if constists of solid metal. What about a thin parabolic shaped foil above the coil? Any other material - perhaps magnetic or ferrite?

Depth would be doubled if all waves go into the ground!

[pebe]

Is there a solution to this?

No.

[mikebg]

Amateur designed ferrite sensor
1. Two RX bobbins connected in series like TWIN LOOP
2. Two TX bobbins connected in series (forming center tap)
3. Two capacitors type MKP (for TX) connected in parallel
4. Two ferrite cores type П (from TV set)

[pebe]

Amateur designed ferrite sensor
1. Two RX bobbins connected in series like TWIN LOOP
2. Two TX bobbins connected in series (forming center tap)
3. Two capacitors type MKP (for TX) connected in parallel
4. Two ferrite cores type П (from TV set)

Using those devices, all the magnetic flux would be concentrated close to, and between, the two pole pieces. There would be very little ground penetration.

[WM6]

Using those devices, all the magnetic flux would be concentrated close to, and between, the two pole pieces. There would be very little ground penetration.

Agree. If one use ferrite core from TV trafo then would be better to build antenna like this:

[Funfinder]

Very interresting ideas!

With this it's possible to create a horizontal scan-rod with which somebody could just go straight ahead without always swinging the coil left and right. Perhaps 10 such small ferrite antennas in a row are needed - and alot TX-power. On the display 10 LEDs in a row, marking a range of 10cm from left to right.


But first back to my reflection-ideas:

Reflector could be discriminated like the RX has to blend out the metal of the TX coil and vice versa, the same with shielded cable that goes from coils to mainboard etc.
Perhaps reflector could made out of special material.

Other problem:
Long wavelenght - and good reflectable UHF- or Micro-waves won't penetrate the ground very well.

But the size of the coils isn't any near the wavelenght like with 40m Amateur-Radio Antennas etc. anyway.

So if a little PI coil can receive such minimal part oh the whole VLF wave / electromagnetic energy - a small reflector also should do his intended job.


But what if the electronic controls the condition of a stabilized oscillating wave (as used in most MDs) and a reflector would force the waves radiating into a special direction? If the reflector is grounded, holden tight so it can't move and the impedance of the coils gets adjusted to the new conditions or "surrounding-parameters"? Still uncontrollable disturbance-factor because of the reflector?

Maybe someone wants to test this.

But perhaps better this coil-design is used:
RX and TX coils are seperated side by side from each other but both are under a reflection shield.

I also can imagine it would work with 10 in a row ferrite-coils under a small diameter upsidedown half-alu-gutter.
But the upmost importance with such designs would be massive physical stability! The movement of the reflector by just a quarter of a millimeter nearer or wider from coil could give the sensitive electronic the impression that there's a metal-object 50cm away or not.


btw. such technique would also work as a good shielding agains high-power-lines or other electromagnetic interferencies coming through the air. And if someone rubs such real-shielded and focused coil directly over the ground the TX-RX- / radiation-quality would raise again!

[Funfinder]

Reflection works!

If you have a Pinpointer adjust it to minimal sensitivity.
Take a metal object and hold it above the horizontal Pinpointer and see from what distance it's recognised.

Now hold the Pinpointer with the same settings over a reflecting iron-plate, alu-foil etc., as close as possible without signal. Better lay it above a book so it won't move.

If now the first object ist tested again from above it will get recognised from a much better distance - in my test the double!


In this very simple experiment 2 effects are responsible:

1st:
The very near adjusted reflector raises sensitivity because it brings the detector just before the very edge of signalizing.

2nd:
In this experiment ca. 1/3 of the radiation beam of the detector gets reflected in the direction of the first object (above) and therefore it's more powerful and concentrated at this direction than before.

We are interrested in the 2nd effect, because adjusting sensitivity (and coil-impedance etc.) is possible anyway.

The proof:
You also can raise the sensitivity of your Pinpointer as high as it goes and the test also will work!

[mikebg]

Reflection works?

Funfinder,
Pinpointer what model you used in this experiment?
Mike BG

[mikebg]

Using those devices, all the magnetic flux would be concentrated close to, and between, the two pole pieces. There would be very little ground penetration.

Pebe is correct. The sensor in posting #3 is not designed for deep search of large objects, but for meteorites and gold prospecting. It surpasses other sensors in the detection of small earrings and gold chains on the beach. The same can be said to trace the wires and pipes in the wall. Since the coil configuration is actually TWIN LOOP, the depth of detecting depends on distance A.
The above ferrite sensor is used in a metal detector, designed by (R)EMI group for a particular search in small meteorites. In the fall to the earth, meteorites do not get stuck deeper. However, they have almost no magnetism and conductivity, therefore, conventional sensors produce weak signals. The ferrite sensor can detect in the conductive and/or magnetic ground such stones, that in the air did not generate a signal.
Other advantages of the sensor are:
- Fine pinpointing because signal is canceled on the plane of symmetry between the RX coils. Trace of this plane is shown in the drawing as a pulled line.
- Too little resistance of TX coil, which provides high efficiency of excitation.
- Suppression of signal from the ground, however, reacted to the difference in soil properties below both RX coils.
- Suppression of signal from distant sources of interference.
- Suppresses the signal from working nearby metal detectors.

[Funfinder]

@ Mike BG
Thanx for the interresting grafix.
I used a White's Bullseye II and a 20cm Alu-Salad-Bowl for that simple test.

btw. my first idea was: using ferrite material as a reflector!

Well, those ferrite coils create a small and very concentrated EM-field, but with reflector the search-distance would increase and simply much more power has to be used, than nowadays wiresearchers or pinpointers do.

But in principle the reflecting must not be restricted only for ferrite-coils.

Your idea with nuggets and meteorites is perfect, and with a "floor-scrubber-design" someone just has to go straight ahead - makes searching much more comfortable!

Evtl. in the middle a hinge so the search unit for stony etc. areas can put into an angle like a snowplow.