Quote:
Originally Posted by MetHerb
Let me ask the question another way, with a UHF antenna with a gain of 16.7 db (the 91XG) and a preamp gain of 26 db and coax and splitter losses of 6 db or less, what would be the "weakest" signal that I could expect under ideal conditions? -15 NM?
What about the same setup with a VHF antenna with a gain of approx. 10 db?
Thanks again!
|
On UHF the tvfool NM level that works with that set-up would vary between -6 db and -22 db. The wide variation occurs because of the way that the receive antenna interacts with the surroundings, plus transmit power variables that occur due to antenna pattern scalloping. However, the likelihood that you'd stumble on the optimum antenna location and height for -22 db NM reception is small.
On VHF with 10 db antenna gain the variation would be between -2 db and -18 db.
There is a ray tracing program called HFTA that can be used to determine what heights are more likely to work well. While intended for frequencies below channel 2 I've used the DOS based predecessor to HFTA (YT) for antenna height calculations for both VHF and UHF TV. The key is to find a height where the main lobe is aimed at the horizon. Other than height, the biggest variable is the slope in front of the antenna.