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Well, I've got an update on this thread:

http://www.avsforum.com/ubb/Forum11/HTML/012772.html


For those of you who have been playing along at home, I've been trying to get DTV signals at my house, which is about 15 miles from the the main Seattle transmission towers.


In the latest episode, I've been playing with a Silver Sensor. No luck inside the house, so I rigged it up to a 15' tall mast I raised on my chimney, putting the antenna about 35' up in the air.


No matter which way I pointed the antenna, the best image I got from the analog UHF channels was blurry with 5-6 ghosts.


Next trick: I rigged up some sheets of aluminum foil mounted on bent coat hangers. Basically, I was trying to create a shield behind the antenna to block some multipath signals.


The shield seemed to help a little: after adding the shield, I only saw 1 or sometimes 2 ghosts.


So now what I'm afraid of is that one of the significant sources of multipath is a hill that is between me and the transmitters. In suspect that what happens is the signal starts at the transmitter, bounces off a hill that is behind me, then subsequently bounces off a hill in front of me, and finally hits me, thus being the source of multipath.


So, now that I've tried 4 different antennas to deal with this, does anybody have any other ideas? Davenlr suggested building a helically wound antenna, so that's probably what I'll try next....




------------------

<yawn>

TiredGuy
 

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Hi Tiredguy,

Maybe you need to change your handle to something else. Sorry to hear of your continued problems. I am now awaiting the Silver Sensor. I prefer to try and do things indoors for the moment. If that is no go, I will try the

helical.


May I ask if you ever "lock" into any DT channels? I don't know how the DTC-100 works, but the Sony HD-100 must detect at least some signal before it will indicate a channel is present. Then the fun starts trying to get enough gain and no multipath. How do you know you have a multipath problem? Maybe it is just not enough gain. I get 13 (18) more reliably than 5 (48) with its higher FOM (figure of merit) on the level indicator of the HD-100. I don't really know how multipath exhibits itself but I suspect it is what I see on 5 (48). FOM of 92 yet every 5 to 10 seconds the picture drops out and the HD-100 goes into "searching for signal" mode.


I am curious how the RCA works in this regard. When you first did an autoscan, did your DTC channels show up. The STB must receive something in order to do this unless you can enter them manually? I can't (as far as I know) do it on the HD-100. When I did and autoscan for the first time, 7.1 DIGT (HD-100 terminology) showed up and I got a picture intermittently with a piece of wire.


When I got the RS Bow Tie, I did another autoscan and got the rest of the Seattle stations to ID themselves.


Questions questions questions!

Bill
 

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I have a similar problem, 17 miles from NYC and hill in the way. Have not been able to pick up any NYC stations with DTC. However, my ability to pick up Philly at 70 miles and all analog UHF stations improved with the addition of a Radio Shack signal attenuator (i.e., reducing the signal strenght). This was a suggestion from the esteemed Mr. Ross.
 

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Hey, TiredGuy, I'm attempting to get a clear kong (16) from 60 miles away on the south end of Fidalgo Island. I'm working my way to getting an hdtv receiver for my new xbr400. I get clear signals from kwpx (33) and a couple of other Bellevue stations, but 16 appears to have multipath problems. I'm using a CM4248 off my deck, pointed across the water. Do you know if trees cause multipath problems?
 

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It sure sounds like your problem is multipath. The only way to cure that is to narrow the lobe of your antenna and increase front-to-side and front-to-back rejection; then you can find the strongest signal (be it direct or reflected) and focus on that one. I think you should aim to pick up the direct signal, even if it means going higher with your antenna to try to get above interfering terrain as much as you can.

You're going to need a sophisticated antenna if multipath is severe. The parabolic UHF antenna made by Channel Master may do the trick, if you can support it physically at the needed height. Failing that, I'd consider experimenting with phasing a bay of yagis together to narrow the lobe. You will probably need expert assistance to accomplish this (unless you are an antenna engineer) but the basic concept is fairly simple, just tough to execute.

Just remember, if multipath is the problem, the key thing is to reduce reception of reflected signals through increasing antenna height to get a clearer shot at the source and/or designing the antenna to minimize unwanted signal azimuths.

Good luck!
 
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