Post by Deleted on Aug 25, 2017 22:15:11 GMT
We all have observed that AM low power signals aren't affected nearly as much by obstructions (such as buildings) as FM.
Radio signal propogation software, such as NEC, obviously can't take buildings and even natural barriers like trees, into consideration.
I've often wondered what exactly that attenuation might be in terms of hard numbers. The only way to really tell is to have a field strength meter, and take measurements at various points - line of sight, inside a building, around the back of a building, etc. Plus, the type of materials used in the building would also be a factor.
I do know that the effect is striking. I put my BETS-1 FM transmitter up high, inside a window sill on the third floor of my townhouse, which gets me above a lot of the obstructions. I can easily receive my signal line of sight on a portable Panasonic shortwave receiver at about 150 meters. That puts me at the opposite end of Osprey Village, and at the back of the further most building. But when I go around the corner of the building (so that it, and a few others, block my line of sight) the signal fades away completely. And it takes a lot to get any sort of reception in the front.
My need for a field strength meter keeps growing.
Radio signal propogation software, such as NEC, obviously can't take buildings and even natural barriers like trees, into consideration.
I've often wondered what exactly that attenuation might be in terms of hard numbers. The only way to really tell is to have a field strength meter, and take measurements at various points - line of sight, inside a building, around the back of a building, etc. Plus, the type of materials used in the building would also be a factor.
I do know that the effect is striking. I put my BETS-1 FM transmitter up high, inside a window sill on the third floor of my townhouse, which gets me above a lot of the obstructions. I can easily receive my signal line of sight on a portable Panasonic shortwave receiver at about 150 meters. That puts me at the opposite end of Osprey Village, and at the back of the further most building. But when I go around the corner of the building (so that it, and a few others, block my line of sight) the signal fades away completely. And it takes a lot to get any sort of reception in the front.
My need for a field strength meter keeps growing.
