Need help getting receiption

[pkmicro]

I have been getting poor receiption lately on some channel that I like such as
KXLA 44.5. I live in San Dimas, Ca about 16 miles from Mt. Wilson. Most of the channel like 2, 4, 7 have been very good. What cause the signal strength to fluctuate so much? I have my antenna installed in the attic(see attached picture of my antenna). My house is 2 story high and my antenna is almost 20 years old from the old analog days. My question is should I get a new antenna something like Multidirectional antenna or is the one I have is good enough? May be I just need to re-align it. I remember when I checked it about a year ago some of the local channel was about 100 but now it's getting only around 92. I am so close to the station and there's nothing is obstructing the antenna except it's inside the attic. what do you think could cause signal loss?. Could the wheather be causing the fluctuation range from 12 to 72? it's has been raining this past couple days. TIA

[Tigerbangs]

You have an old Radio Shack VU-90, which, in it's best days, was a marginal performer. When you add the disadvantage of being installed in the attic to the mix, you have the potential for some trouble. Alignment would be my first suggestion, however, if your cable is 20 years old, then that would be my next guess. To find out what your proper alignment should be, use the TVFool.com station identifier here:
http://www.tvfool.com/index.php?option=com_wrapper&Itemid=29

based on the San Dimas zip code, your correct alignment should be just about 290 degrees by the compass.

If you want to be sure that you get everything reliably, mount a new Winegard HD-7694P on the roof with all new cable.

[pkmicro]

Thanks for your quick response. I went up on the attic this afternoon and re-align the antenna by moving it to point south and slide it up a little bit and I was able to receive about 78 - 79% on Channel 44.5. But now I lost Channel 9(KCAL) & Channel 58(KLCS). No signal at all. I check the TV signal locator in this site and these 2 channel should be around 284 degree, since I could get around 79% on Channel 44.5 why couldn't I get any signal on 9 & 58, that is very strange. How do I align the antenna exactly at 284 degree? I went outside and check my neightbor and found out that there's a big maple tree that looks like it's in the path of my antenna & Mt. Wilson Transmission Station. Wonder if that tree could cause any problem? Would a new Multi-directional antenna be able to let me receive those 2 channel?

[Tigerbangs]

You are experiencing a problem called multipath, where your antenna is receiving a signal reflected by the structure of the house and direct signal from the transmitter almost simultaneously: it's a very common problem with attic and indoor-mounted antennas. Because the wavelength of TV signals are different according to the transmitting frequency, or channel, the problem is often selective, and might not be seen on all of your channels. A multi-directional antenna is not a good solution for you because it has no ability to reject multipath, and all of your TV stations come from one location, anyway.

Your best solution is to mount a new antenna outdoors, using all-new equipment and cable, as I mentioned before. Your multipath issues will go away if your antenna is mounted at the highest point of your house, with an unobstructed view of the transmitters. Oddly enough, this problem is more often seen in very strong signal areas than in medium or weak signal areas.