Originally Posted by Monte324
I'm guessing I'd have to put the antenna another 20 feet higher than my roof to actually see sutro tower. And I'm not going to do that. Does LOS prevent multipath or just reduce it?
Someone mentioned my antenna might be overkill. Does that mean it might be too strong and picking up other signals that are interfering or just saying it is better than needed, but not implying anything by that?
When you have LOS, in almost all cases the main path signal is so dominant that multipath is not an issue. There are still reflections so multipath exists but the reflections are normally weak compared to the main path signal. LOS within about 30 miles virtually guarantees perfect reception. Reception problems at < 30 miles are almost always from poor antenna siting no matter what that may imply. When you get farther from the transmitter atmospheric conditions become more significant and can cause signals to be attenuated resulting in periods of poor or no reception. This certainly is not always the case but it is frequently reported.
There are a couple of kinds of multipath. One occurs when obstacles (like trees) on the main path cause the signal to be broken into multiple paths. No antenna is going to fix that because all the signals are in the same direction and getting above the vegetation is the only solution although sometimes moving the antenna can improve that situation if it doesn't make another channel worse. Then there are reflections that come from widely varying directions. A highly directional antenna can improve that a lot.
I have both of those problems here. I need highly directional antennas to reduce the reflections enough so I can receive the stations at all but multiple signals on the main path cause me to have lower SNRs than what the strength of the signals would suggest. I've tried moving the antennas around and SNRs go up and down but there doesn't seem to be any magic location for all the stations.
I don't believe your antenna is overkill.
Although I read it all the time, I have no answer when people tell me they don't want to put up the antenna needed to receive the stations they want. If you have the maximum installation you're willing to do, then you have to accept whatever that receives.
BTW, when you said your antenna was at 8', I assumed that to mean 8' off the ground and not 8' above the roof. But reading your other comments I may have misinterpreted that. If it's 8' off the ground, then a roof installation should improve things a lot. If it's 8' above the roof then yes, you'd probably have to go much higher.