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Discussion Starter · #1 ·
I'm having a problem that's frustrating me to no end, and I'm hoping someone can help. This message might be a little long winded, but the problem is odd, and I'm really hoping someone here can help.


I've recently purchased a hidef tuner and antenna. (AccessDTV and Silver Sensor) I'm having some serious problems getting the antenna set up right.


When I try to tune a channel, the accessDTV software shows the signal fluctuating wildly. It'll go from one bar, to 3/4 strength, then back down in a second. The picture will be fine for a while, then I inevitably get a frozen picture, or artifacts. I've tried 2 different silver sensors (one Antiference branded, one Zenith) as well as an amplified Radio Shack indoor antenna (15-1880) Both silver sensors show this behavior, and the Rat Shack deal gets little to no signal at all.


Here's the strange part. If I touch the part of the antenna that connects to the coax cable with my hand, the signal will lock near full strength and stay that way. This also happens sometimes when I jiggle the coax connectors. I've tried different coax cables, and multiple antennas.


I'm about 29 miles from the source of all channels, so I realize I'm stretching it a bit with an indoor antenna. Problem is, I'm in an apartment and they've got some pretty fierce restrictions on outdoor antennas (insurance, professional installation, etc..) so I'm trying to avoid going that route. The fact that I can get a lock when touching the antenna or jiggling the connectors seems to me to indicate there is a strong enough signal in the air.


Is this some sort of interference problem? Will an amplifier help?
 

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Sounds like a multi-path problem. Your signal is coming in very strong, but multiple reflections of that signal are being received simultainiously. I'm not sure how to address it. But search around I'm sure there is an answer here somewhere.
 

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Discussion Starter · #3 ·
To see if I was getting any multipath, I hooked the antenna up to the TV and took a look at some of the analog stations, which are broadcast from the same location.


The picture was pretty fuzzy, and on my HDTV it looked pretty pixelated and garbled. I *THINK* I saw some minor ghosting, but it seemed minor if it was there at all. It looked like there was a shadow on some characters, but it moved in synch with the video. In the past, at another location, I'd seen ghosts that were inches from the original, and lagged behind noticably.. in my instance it wasn't that severe, and I honestly may have been imagining it through the garbled picture.


Any other ideas?
 

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My guess would be some sort of local interference, maybe from a defective Pat 15 device like a cordless phone, baby monitor, etc. I would say get a better antenna since you can improve things by touching it. The fact that you can use a very poor antenna (your body) to improve the signal means that the antenna you are using is pretty poor. If all you HD stations are UHF, try a quad bowtie (and don't worry about how ugly it is).


Ernie
 

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Discussion Starter · #5 ·
Well, I do have quite a bit of wireless floating around my apartment. This includes;


Cordless phone (rarely used, and not in use during my problems thus far)

802.11b wireless LAN (I've got the g equipment, just haven't installed it yet.)

Gyration keyboard/mouse


I'm definitely open to trying a new antenna if there's a chance it'll help. But like I said initially, I really need to keep it indoor. The hoops I have to jump through for an outdoor are crazy, and while they allow me to place the antenna I can't drill a hole for the cable to pass through.


Does anyone have any suggestions, either for different indoor antennas to try, an amp/filter that may do the trick, or anything else? I'm at wit's end.
 

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The Silver Sensor is generally considered one of the best indoor antennas. How far away are the stations? Can you see that direction from one of your windows, or are you on the opposite side of the appartment building. If you can see in the direction of the towers, put the Silver Sensor next to the window and aim it toward the towers.
 

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Discussion Starter · #7 ·
The transmitters are 29 miles away from me. I have a large patio door facing that direction, and the antenna is within a few feet of it. I've tried it with the antenna closer, and with the doors open as well. My results are somewhat worse when it's closer to the windows, probably as a result of resting on the ground as opposed to being 7 feet off the ground on top of my bookshelves. I'm in a second floor apartment also.


Since I have two silver sensors currently (though one will likely be returned.. I thought maybe the first one was faulty) I'm considering combining the two of them to see if that helps. My understanding is that having multiple antennas can sometimes help with multipath problems, if that is really what I'm experiencing.
 

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I think 29 miles is pushing it for the SS. I had one for towers that were 15 miles away, and it did alright, except for a PBS DT that was at 80 KW. It would do exactly what you're describing. I replaced it with a CM 4221, but I have the luxury of being able to put it in my garage rafters (where I also had the SS). But the bottom line is this - the CM is better than the SS. I know most people sing the praises of the SS, and it may be one of the better indoor antennas, but it does have its limitations. And, again, I think when you're 29 miles away, you pushing the limits. Any indoor antenna loses half its ability compared to being outdoors. If there's a place you can put the CM, try it.
 

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Discussion Starter · #9 ·
Am I reading the dimensions right on the CM 4221 at 4"x20"? That's pretty small.. I could probably find a place for that indoors.
 

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Discussion Starter · #13 ·
Hmm.. that's pretty big for indoors.. maybe in a closet or something, but there's no easy way to hide cables, and my closets have aluminum doors which I'd guess wouldn't be good.


Bob Dycus - I've seen little FM traps at Radio Shack that're basically gender changers but about 2" long. Is that the sort of thing you're referring to Maybe I can get by with the trap without the amplifier, though I'll try both if need be.
 

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Discussion Starter · #14 ·
I realized something about my distance number above. I said 29 miles, but I got that number using mapquest with my address, and the address of the transmitters. the signal actually goes in a more direct route though, probably more like 23 miles... maybe even a bit less.
 

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If its multipath, you can use 2 silver sensors, positioned exactly1/2 wavelength from each other, to eliminate of of the recetion paths. Google dual silver sensor multipath, the guy seems to know his stuff...
 

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jjarmoc,


I used to have a couple of SS's that I experimented with indoors at 54mi from my local towers,and was able to pick up a couple of stations.Two worked much better than one and a good preamp was necessary.You really need a preamp(read mandatory) such as a CM7775 or 7777,hook the two SS's together using a regular hybrid splitter(used backwards),then attach the splitter to the preamp input with a short piece of coax or get the gold double ended male coax connector from RS.


The SS's will probably work best about a foot apart and one slightly ahead of the other one.Experimentation will be in order for sure.


good luck
 

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Your problem isn't multipath, from your description.


it sounds like a signal strength issue. Note you said the analog stations were snowy , indicating a weak signal. When you touch the antenna, your body becomes part of the antenna system. In effect your increasing the gain of the system, albeit in a sloppy way. You may be catching more multipath, but in spite of what you read here sometimes that's not always a bad thing (short-delay multipath within the range of the receiver's equalizer is summed to the main signal in the receiver).


You could try the old tin-foil-on-the-antenna trick, or substitute a length of wire for your body. Just like with analog reception, this goes with the territory with indoor antennas. Or an amplifier may help.


BTW, look at the FCC link in my signature; some/all of your apartment restrictions may now be illegal under Federal law.
 
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