OTA tuning troubles

[TPK]

Hello there...

I am trying to get my media center PC dialed with an OTA antenna so I can record DTV network shows....  It seems that I am having some troubles with some stations, and I am not sure why...

NBC (4) and CBS (58) seem to come in okay without any trouble...

However, Fox (6) and ABC (12) seem to come in okay sometimes, but sometimes I experience lots of drop-outs and pixelation...  I think it may be related to the moisture content in the air (the more moisture, the less it works) but that is just a guess of mine why it sometimes comes through without a problem and sometimes not...

I live in Bayside (that would be next to the lake, immediately south of the Milwaukee/Ozaukee county border), so I believe I SHOULD be close enough to the towers to use this antenna without any problems, but maybe I need something better??

My setup includes a rediculously over-powered PC with the Vista media center, a hauppage 1800 card, and a radio shack indoor/outdoor antenna (links below):

Card: http://www.newegg.com/Product/Product.aspx?Item=N82E16815116015
Antenna: http://www.radioshack.com/product/index.jsp?productId=2348191

I have the antenna mounted in my attic facing just slightly upwards (well, now that I look at it again, its actually pointed straight out horizontally, maybe I should tilt it upwards?) and almost directly south, but just slightly west (my best guess according to what anntenaweb.org says)...

I do, however, have tall trees immediatly south of my house, so perhaps those are causing some interferrence, I don't know....  Its also possible that the siding of my house might be causing interferrence (Im not even sure what its made of)...  I was thinking of just mounting this antenna on my roof rather than in my attic, but I would like to not do that unless I have to...

Whats irking me the most is that media center signal strength is reporting all of these channels at full strength (6 green bars) while I am getting these drop-outs

So what would be my best shot at getting a clear signal??  Should I get a better antenna??  Should I get a better tuner card???  Am I wrong to expect clear DTV signal based on where I live??

[ArgMeMatey]

I would suspect your trees.  Cut them down.    

Or you could try the antenna outdoors.  Or higher.  Or make sure your antenna does not have a preamp.  You should not need that.  Or wait for others to weigh in.  Somebody may have a better idea.  

I live less than 3 miles from all of the towers, in Shorewood, and use an indoor antenna that is one step removed from a coat hanger.  When it is windy my reception is much worse.  More trouble on 58, 36 and 12, less on 4, 55, and 6.  I think I am slightly closer to the latter.

[TDP]

I suspect you have a problem with multi-path interference.  This is when the same signal gets to the antenna at different time, canceling the signal out.  Hence why it drops out.  You are close enough to the towers that the signal is equally as strong from the main source (the tower) and the reflection (any flat surface nearby).  You may be able to resolve this by adjusting the antenna in the attic to try to reduce the level of the reflection, or you may have to mount the antenna so that it has a fairly clean path to the towers.

[Buy_The_Tie]

I would agree, that multipath is likely the problem.

I have this antenna mounted on the roof:

http://www.radioshack.com/product/index.jsp?productId=2103088

I have had good results.  It is likely more directional, and may be better at helping you ignore the multi-path signals.

You did save your receipt, didn't you?  

[AA9VI]

a few suggestions:
1) put a variable attenuator (sold at radio slack) inline.  Change the attenuation level, observe the results.  Maybe you have overload?
2) aim the antenna NOT directly at the tower but off 30-45 degrees or something like that.  if it is multipath, you may be able to steer away from the secondary signal and get enough of the main signal from the transmitter.
3) use higher quality coax.  use at least RG-6.  RG-6QS is even better.  

Getting the antenna outdoors will definitely cut down on the variables to your problem.