How long can coax cables go and any conflicts before HDTV OTA signal losses? - AVS Forum
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post #1 of 55 Old 06-28-2012, 10:49 AM - Thread Starter
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Hello all.

What's the maximum coax cable lengths can be before they start losing signals from HDTV OTA feeds? Also, are there anything that can conflict them? The reason why I am asking because I noticed some rooms, in a big house, can get more channels and better feeds than others. It could be the old coax cables (used to be for Dish service from the previous owners) or something.

Thank you in advance. smile.gif
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post #2 of 55 Old 06-28-2012, 10:50 AM
 
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You start losing some signal the longer the cable is. for RG6 it might be about 1 dB for every 17 feet or so.
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post #3 of 55 Old 06-28-2012, 10:54 AM - Thread Starter
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Wow, 17 feet already? How does one determine if the old coax cables are RG6? Does Dish use them?

So how does one improve this without replacing? The house is about 3,900 feet. The antenna is in the front yard and its coax cables go to multiple rooms. http://i.imgur.com/LTao8.jpg for an aerial shot from the sky.
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post #4 of 55 Old 06-28-2012, 11:10 AM
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Your antenna is 3900' from the entrance to the house? Wow! You have a big front yard.

Easiet way to provide signals to all TV's is a pre-amp at the antenna and a distribution amp in the home.

Or... move the antenna 3/4 miles closer to the house. biggrin.gif
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post #5 of 55 Old 06-28-2012, 11:11 AM - Thread Starter
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Quote:
Originally Posted by Ratman View Post

Your antenna is 3900' from the entrance to the house? Wow! You have a big front yard.
Easiet way to provide signals to all TV's is a pre-amp at the antenna and a distribution amp in the home.
Or... move the antenna 3/4 miles closer to the house. biggrin.gif
Crap, I said that wrong. I revised my previous post. frown.gif I included an aerial photo. Sorry!
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post #6 of 55 Old 06-28-2012, 11:12 AM
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.860QR cable is going to cost $1.00 a foot not counting conduit, plus you will need at least 2 quality amplifiers to drive the signal. I presume you would it buried and want it conduit, there is more cost there. I would bring that antenna closer...smile.gif

All Comments made are my own and not of my employer.
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post #7 of 55 Old 06-28-2012, 11:17 AM
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I'd suggest starting over. wink.gif

Provide accurate info.

Where is antenna mounted?
How many TV's?
How long are the cable runs?
What splitters are being used?
How and where are the splits configured?
Are all the runs RG6 coax?

That's just a suggestion for a starting point.
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post #8 of 55 Old 06-28-2012, 11:34 AM - Thread Starter
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Quote:
Originally Posted by Ratman View Post

I'd suggest starting over. wink.gif
Provide accurate info.
Where is antenna mounted?
How many TV's?
How long are the cable runs?
What splitters are being used?
How and where are the splits configured?
Are all the runs RG6 coax?
That's just a suggestion for a starting point.
RCA ANT751 antenna in front of the house's kitchen near the garage wall in the corner, under the roof.
Four TVs (currently, a portable ATSC and a CRT+Zeinth converter box; more will come).
No idea how long the cables are. They are from previous owners with Dish service. They go to four different rooms in the 3,900 feet house. See my earlier link with the aerial shot to get an idea where Dish network (RCA antenna is near it on its left/west)
I believe just one splitter since they went from the Dish satellite, in the attic, into the rooms. It's dusty and lots of cables up there.
RG6 coax, I have no idea. How can I tell? They're old though from previous owners' Dish.

I hope that helps?
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post #9 of 55 Old 06-28-2012, 12:20 PM
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Quote:
Originally Posted by phildaant View Post

RG6 coax, I have no idea. How can I tell? They're old though from previous owners' Dish.

The chart at http://en.wikipedia.org/wiki/Coaxial_cable#Standards may answer some of your questions. I see you're getting the same answers here that you got on Usenet. wink.gif
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post #10 of 55 Old 06-28-2012, 12:23 PM
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I'm sorry, but I have no idea. Hopefully someone will struggle through this task and provide some info for you. Based on what I can determine from only a photo, I'd suggest you antenna is mounted too low and is probably aiming through trees. What's inside your home and how it's all connected is not worth "my" time.

I apologize if I sound too blunt, but it's quite difficult to provide recommendations/suggestions based on an aerial photo of a roof. wink.gif

Good luck.
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post #11 of 55 Old 06-28-2012, 12:25 PM - Thread Starter
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Quote:
Originally Posted by domino92024 View Post

The chart at http://en.wikipedia.org/wiki/Coaxial_cable#Standards may answer some of your questions. I see you're getting the same answers here that you got on Usenet. wink.gif
Hmmph, that's all technical. No photograph/photos.? I know the cable ends are either the screw types. frown.gif
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post #12 of 55 Old 06-28-2012, 12:49 PM
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My RG-6 cable run from the antenna (mounted 15' above the metal roof apex) is about 115 uninterrupted feet where it comes into the garage, connects to an old Motorola Signal Booster, and into a 3-way splitter, which sends the signal to 3 tvs. One of which is our HDTV. Signal is always strong and trouble-free.
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post #13 of 55 Old 06-28-2012, 12:58 PM
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I assume from the picture that you are trying to say that your house is 39 thousand SQUARE feet. That along with the picture would make your house something like seventy by sixty feet. That would make a straight line run to any place in the house less than 100 feet. You won't have straight runs but most locations will not be at the max distance so 100 feet is as good a guess as can be made without you doing some measuring. Good RG 6 losses about 2 to 7 dB for a hundred foot run depending on the channel. Higher physical channels lose the most. A four way splitter loses another about 8 to 10 dB.
So the question is how much you can afford to lose and that depends on the signal that the antenna delivers to the cable. To get a rough idea of that provide TVfool results for your location. If none of your signals are very strong the cable and splitter loses can be overcome with an amplifier. With strong signals an amplifier often does more harm that good.
John
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post #14 of 55 Old 06-28-2012, 01:14 PM - Thread Starter
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Quote:
Originally Posted by ctdish View Post

I assume from the picture that you are trying to say that your house is 39 thousand SQUARE feet. That along with the picture would make your house something like seventy by sixty feet. That would make a straight line run to any place in the house less than 100 feet. You won't have straight runs but most locations will not be at the max distance so 100 feet is as good a guess as can be made without you doing some measuring. Good RG 6 losses about 2 to 7 dB for a hundred foot run depending on the channel. Higher physical channels lose the most. A four way splitter loses another about 8 to 10 dB.
So the question is how much you can afford to lose and that depends on the signal that the antenna delivers to the cable. To get a rough idea of that provide TVfool results for your location. If none of your signals are very strong the cable and splitter loses can be overcome with an amplifier. With strong signals an amplifier often does more harm that good.
John
TV Fool Reports as of 6/28/2012:
0 ft. height entered: http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d13490909db0c9f
5 ft. height entered: http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d1349e1250c5c04
10 ft. height entered: http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d134986774edc54

And my parents doesn't want any antenna on the roof top or outside visible, or in the middle of the kitchen (CM-4228HD). However, they did allow to mount it in the front (RCA ANT751) where the best outdoor spot. frown.gif
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post #15 of 55 Old 06-28-2012, 08:04 PM
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Have you tried using a pre-Amp? So the signal is amplified right at the antenna.

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post #16 of 55 Old 06-28-2012, 08:56 PM - Thread Starter
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Originally Posted by aaronwt View Post

Have you tried using a pre-Amp? So the signal is amplified right at the antenna.
No, not yet but will that really work in my situation? If so, then which preamp do I get that is returnable if it doesn't work? I have these local stores: Fry's Electronics, Best Buy, Walmart, Costco, K-Mart, Target, Sears, Radio Shack, etc.
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post #17 of 55 Old 06-29-2012, 12:54 AM
 
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Quote:
Originally Posted by Otto Pylot View Post

My RG-6 cable run from the antenna (mounted 15' above the metal roof apex) is about 115 uninterrupted feet where it comes into the garage, connects to an old Motorola Signal Booster, and into a 3-way splitter, which sends the signal to 3 tvs. One of which is our HDTV. Signal is always strong and trouble-free.

you could have stronger signals from the start
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post #18 of 55 Old 06-29-2012, 01:15 AM
 
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Quote:
Originally Posted by phildaant View Post

No, not yet but will that really work in my situation? If so, then which preamp do I get that is returnable if it doesn't work? I have these local stores: Fry's Electronics, Best Buy, Walmart, Costco, K-Mart, Target, Sears, Radio Shack, etc.

a pre-amp will help it will mitigate at least some of the signal loss especially with your signal levels. Also I should say those losses were assuming UHF channel usage I see many of your station are hi-VHF so for them your losses would be less. for hi-VHF your losses would be about 1 dB for every 25 feet. For UHF is would be about 1 dB for every 15 feet. Also if you have 4 TVs connected and you're using a 4 way splitter that's a loss of 7 dB right there. You'll probably have to go online to get a decent pre-amp.

Also your antenna is probably fine for the hi-VHF because they are the strongest signals but it is totally inadequate for the UHF channels if the TVFool results you posted are correct.
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post #19 of 55 Old 06-29-2012, 08:33 AM
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Originally Posted by BCF68 View Post

you could have stronger signals from the start

That is very true. I got the signal booster years ago when everything was still analog because our local Fox affiliate was weak at times. I never removed the signal booster when everything went digital because Fox et al were just fine (if it ain't broke, don't fix it), even from about 60 miles (direct LOS) from the towers.
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post #20 of 55 Old 06-29-2012, 09:42 AM - Thread Starter
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A while ago, there was a coax cable connected to a power AC (http://www.dennysantennaservice.com/image/32723968_scaled_352x298.jpg as an example online) in one of the small rooms (closest one to the main coax cable to the satellite dish and before its splitter) for the previous owners' Dish TV service. I assume this a preamp? This was removed, so maybe this is why OTA does poorly in the rooms since this premap was removed? I wonder if we should put it back (not sure if it is compatible with OTA?), and it will work better? However, this was not outside/in the attic near the antenna's main coax cable before the splitter since it was in a small room. I don't think the attic has any power outlets.
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post #21 of 55 Old 06-29-2012, 02:01 PM
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Quote:
Originally Posted by ctdish View Post

I assume from the picture that you are trying to say that your house is 39 thousand SQUARE feet. That along with the picture would make your house something like seventy by sixty feet.
You meant 3900, not 39000. That would be a huge house ! biggrin.gif

I would say using a RF distribution amp (powered splitter rather than a passive splitter) would certainly help you out, since you lose at least 3 dB each time the signal is split in two. Since you live in a 39 hundred square foot house (and not a 39 thousand square foot house! tongue.gif) Chances are these are more significant losses than those from long coax runs. For example I use a Leviton (don't recall the model number off the top of my head) that has 3 RF inputs and 8 outputs and output gain adjustable from -5 dB to 15 dB. Works considerably better than passive splitter did.

(edited "an amplified" to "a passive")
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post #22 of 55 Old 06-29-2012, 02:09 PM - Thread Starter
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Quote:
Originally Posted by P719C1 View Post

You meant 3900, not 39000. That would be a huge house ! biggrin.gif
I would say using a RF distribution amp (powered splitter rather than an amplified splitter) would certainly help you out, since you lose at least 3 dB each time the signal is split in two. Since you live in a 39 hundred square foot house (and not a 39 thousand square foot house! tongue.gif) Chances are these are more significant losses than those from long coax runs. For example I use a Leviton (don't recall the model number off the top of my head) that has 3 RF inputs and 8 outputs and output gain adjustable from -5 dB to 15 dB. Works considerably better than passive splitter did.
Hmm, none of the local retail stores seem to carry RF distribution amp from Leviton. frown.gif
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post #23 of 55 Old 06-29-2012, 03:36 PM - Thread Starter
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Would these preamps be OK from Radio Shack to try and return if needed?
1. http://www.radioshack.com/product/index.jsp?productId=3770519 (Model: 15-321 | Catalog #: 15-321)
2. http://www.radioshack.com/product/index.jsp?productId=3780245 (Model: 15-259 | Catalog #: 15-259)
Reviews are three and four stars, and they only go to two TVs. At least, they can be returned. wink.gif
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post #24 of 55 Old 06-30-2012, 10:10 AM
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Originally Posted by phildaant View Post

Would these preamps be OK from Radio Shack to try and return if needed?
1. http://www.radioshack.com/product/index.jsp?productId=3770519 (Model: 15-321 | Catalog #: 15-321)
2. http://www.radioshack.com/product/index.jsp?productId=3780245 (Model: 15-259 | Catalog #: 15-259)
Reviews are three and four stars, and they only go to two TVs. At least, they can be returned. wink.gif


It's worth a try, but I'd say for your application it may be worth it to look on eBay, Amazon, etc. for one that has more outputs. You're likely to get a better deal too. eBay is where I got my Leviton unit from.
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post #25 of 55 Old 06-30-2012, 10:54 AM - Thread Starter
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Originally Posted by P719C1 View Post

It's worth a try, but I'd say for your application it may be worth it to look on eBay, Amazon, etc. for one that has more outputs. You're likely to get a better deal too. eBay is where I got my Leviton unit from.
Well, I want the local retail stores to quickly buy, return, etc. I can get the same model that work for cheaper prices to pricematch later.
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post #26 of 55 Old 06-30-2012, 03:18 PM
 
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Quote:
Originally Posted by phildaant View Post

Would these preamps be OK from Radio Shack to try and return if needed?
1. http://www.radioshack.com/product/index.jsp?productId=3770519 (Model: 15-321 | Catalog #: 15-321)
2. http://www.radioshack.com/product/index.jsp?productId=3780245 (Model: 15-259 | Catalog #: 15-259)
Reviews are three and four stars, and they only go to two TVs. At least, they can be returned. wink.gif

They go to as many TV's as you want. The port that goes out the the TV you would connect to the cord going into the house that connect all the TVs. .Anyways unless they've changed Radio Shack amps have always been crap. Also I don't think those are for outdoor which would make them amps not pre-amp. You need a pre-amp.
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post #27 of 55 Old 06-30-2012, 04:15 PM
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Maybe he doesn't need a pre-amp or distribution amp. It's possible that the antenna is not aimed properly, not mounted properly, not the best antenna and/or the splitters and/or coax in the home is less than optimal.

IMHO, you can add pre-amps or distribution amps for a SWAG, but if you have a bad antenna/aiming/mounting, bad reception, bad cables/connectors/splitters.... all you do is amplify a bad signal.
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post #28 of 55 Old 06-30-2012, 04:21 PM - Thread Starter
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Quote:
Originally Posted by Ratman View Post

Maybe he doesn't need a pre-amp or distribution amp. It's possible that the antenna is not aimed properly, not mounted properly, not the best antenna and/or the splitters and/or coax in the home is less than optimal.
IMHO, you can add pre-amps or distribution amps for a SWAG, but if you have a bad antenna/aiming/mounting, bad reception, bad cables/connectors/splitters.... all you do is amplify a bad signal.
It's definitely not the antenna since hooking up directly to a portable ATSC TV is fine.
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post #29 of 55 Old 06-30-2012, 07:14 PM
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Quote:
Originally Posted by phildaant View Post

It's definitely not the antenna since hooking up directly to a portable ATSC TV is fine.

Besides concerns about the in-house distribution system there is tremendous differences in TV tuners. Since you have established a baseline with the portable TV try connecting it in each room to see if reception is the same or different - that will determine if the problem is with the specific TVs or your distribution system.

Properly installed coax for a Sat system should be fine for OTA.
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post #30 of 55 Old 06-30-2012, 07:20 PM - Thread Starter
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Originally Posted by Tschmidt View Post

Besides concerns about the in-house distribution system there is tremendous differences in TV tuners. Since you have established a baseline with the portable TV try connecting it in each room to see if reception is the same or different - that will determine if the problem is with the specific TVs or your distribution system.
Properly installed coax for a Sat system should be fine for OTA.
I already did. Not all the same. It seems like the farther rooms are weaker. Hence either cables are bad/old or something else.
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