Hi
ozanmeklih,
A good rule of thumb is to keep 1/4 of the wavelength in the material between the TX and RX.
But, there are exceptions and ways to make this shorter. None the less, it is a good starting
point, dipole antennas do have lots of ringing and close proximity of the TX and RX can actually
make this even worse. That's why some manufacturers have such large antennas to reduce this
effect, but this is something you need to test with your equipment.
Georadarinfo, you are mistaken, the distance between the TX and RX bear no influence whatsoever
on penetration depth if the travel time through the media is not bigger than the penetration depth
of the device. GPR doesn't work the same way as resistivity probes where that distance does
have a major impact, this is a common mistake from geophysicists that didn't have much exposure to
GPR, but lots of experience with resistivity methods .
On a completely another plane, the distance between the TX and RX will indeed add lots of clutter to the top
part of the data making difficult to see shallow objects, perhaps that's what you meant. But, it is
a design task of any antenna designer to reduce as much as possible this effect to obtain better data,
this sometimes is called "top resolution".
Finally 50cm between the TX and RX for a 300MHz sounds excessive and unnecessary, for a 100MHz on the
other hand it sounds a little bit too little unless working on a heavily saturated media. You see "loza" or not
the EM propagates through the media according to the laws of physics not manufacturers
When it comes to GPR it is important to explain the "why" not only the "what".
Regards,