Quote:
Originally Posted by ionios
i have another question for, you in your plan were we connect the generator?
also the antenna were you have in your plan it is for air transmit,
if we like to have both air and ground what we do?
Thank you.
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portable VLF transmitters and receivers almost always use coil type antennas because they are more efficient than telescoping antennas. The coil type is also much more directional.
The portable telescoping antenna works poorly at VLF frequencies. The telescoping antennas are usually reserved for higher frequencies than the 30 KHz that you want to broadcast.
VLF at 30KHz will broadcast easily into the air, and will also penetrate from the air into the ground at least 10 meters deep depending on the soil. If the soil is not conductive, then it can penetrate deeper. When you make the frequency lower, then the same power of VLF will penetrate into the ground deeper. I would not be surprised if you sent signals to 50 meters using 12 KHz, but it depends on the soil conductivity and how much power you are broadcasting.
Geologists set up their portable transmitters on the ground, then they usually put a cable on the ground in a single loop that can be more than 1Km diameter to make a circle around the place where they want to locate and measure anomalies under the ground.
They want to make a very even vertical VLF magnetic field that they can walk through the interior of, and measure the variations of the field strength with their receivers.
They can detect rock formations and mineral deposits or ores and metals or tanks under the ground up to 50 meters deep, and sometimes deeper.
I think you will find that WM6 is very expert for building transmitting equipment.
And I believe WM6 is correct that you will be wise to experiment with different kinds of transmitting and receiving antenna coils.
You will find that the coils he recommends will always work better than a telescoping antenna for VLF frequencies.
You will see there is no need to put parts of the antenna under the ground to penetrate deep.
The problem will be to locate metal things that are small.
I think it will take much experimenting before you will find a good combination of transmitter and receiver to be able to detect metal things under the ground that are small enough for you to carry in your hand.
Best wishes,
J_P