OTA Antenna through cat5? - AVS Forum
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post #1 of 9 Old 01-28-2008, 08:17 AM - Thread Starter
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Hello,

Can an over-the-air antenna signal be sent over Cat5? I previously diplexed my OTA attenna with a DirecTV satellite signal on RG6, ran them on a single cable into the house, and then split them with a diplexer. This worked flawlessly. I recently installed the new DirecTV MPEG4 satellite, which cannot be diplexed with an OTA signal. So all of my RG6 runs from the roof (I had four, so much for future proofing) are being used by the satellite. I do have both cat5 and fiber run to the roof, but know of no way to use them to deliver an OTA antenna signal. Is there any device that can connect RG6 to cat5 then back again, without loss of the OTA signal?

Thanks for your help.

Brian
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post #2 of 9 Old 01-28-2008, 08:25 AM
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Can you use a diplexer...to split the Sat and antenna signal on one RG6. I do not believe cat5 is the answer for use as an antenna feed.

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post #3 of 9 Old 01-28-2008, 08:31 AM - Thread Starter
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AV Doogie,

It appears that the MPEG4 signal on the new DirecTV satellite cannot be diplexed (I have tried to diplex before the multiswitch, to no avail), which is a common complaint with the new system. Everytime, you think that you have future-proofed, the future proves you wrong.

Brian
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post #4 of 9 Old 01-29-2008, 05:47 AM
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Quote:
Originally Posted by bmarr View Post

Hello,

Can an over-the-air antenna signal be sent over Cat5? I previously diplexed my OTA attenna with a DirecTV satellite signal on RG6, ran them on a single cable into the house, and then split them with a diplexer. This worked flawlessly. I recently installed the new DirecTV MPEG4 satellite, which cannot be diplexed with an OTA signal. So all of my RG6 runs from the roof (I had four, so much for future proofing) are being used by the satellite. I do have both cat5 and fiber run to the roof, but know of no way to use them to deliver an OTA antenna signal. Is there any device that can connect RG6 to cat5 then back again, without loss of the OTA signal?

Thanks for your help.

Brian

I'm sorry, but the answer is no since you are looking for no additional loss to the signal. To be honest, I've never tried using a balun for antenna signal, but due to the frequency range required, I'm guessing it would not work very well at all. This doesn't even begin to address issues you will have like antenna pre-amps.

I think your only good option is to run some more coax to the outside. While you are at it, I would make sure you've got 5 or more coax total run for future use or multiple sat receivers.

Best of luck,

Carl

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post #5 of 9 Old 01-29-2008, 06:32 AM
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Originally Posted by fedders View Post

I'm sorry, but the answer is no since you are looking for no additional loss to the signal. To be honest, I've never tried using a balun for antenna signal, but due to the frequency range required, I'm guessing it would not work very well at all. This doesn't even begin to address issues you will have like antenna pre-amps.

I think your only good option is to run some more coax to the outside. While you are at it, I would make sure you've got 5 or more coax total run for future use or multiple sat receivers.

Best of luck,

Carl

We run at a minimum 7 coax plus ground from the roof to the central hub. You just never know when that extra cable might be needed. I always tell the guys if they are not sure, then run an extra wire. I will never get mad if there are a couple extra cables to dress up. But if we are short one...
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post #6 of 9 Old 01-29-2008, 05:10 PM
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Quote:
Originally Posted by bmarr View Post

Hello,

Can an over-the-air antenna signal be sent over Cat5? I previously diplexed my OTA attenna with a DirecTV satellite signal on RG6, ran them on a single cable into the house, and then split them with a diplexer. This worked flawlessly. I recently installed the new DirecTV MPEG4 satellite, which cannot be diplexed with an OTA signal. So all of my RG6 runs from the roof (I had four, so much for future proofing) are being used by the satellite. I do have both cat5 and fiber run to the roof, but know of no way to use them to deliver an OTA antenna signal. Is there any device that can connect RG6 to cat5 then back again, without loss of the OTA signal?

Thanks for your help.

Brian


Please tell me more about the OTA and Direct w/diplexers. I have been kicking this around and am about to buy an Antenna...just couldn't be sure if it would work. I have Dish, but I'm sure it's the same...Before or after the amp/splitter.? I have 1 diplexer for the dual tuner DVR as it is...will this be aproblem?

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post #7 of 9 Old 01-29-2008, 05:56 PM
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Brian-

Cat-5 is an unshielded twisted pair (UTP) cable with a characteristic impedance of about 110 ohms. It was designed for balanced data/phone and not for RF applications, however it would be possible in theory to press it into service to connect an OTA antenna to a TV set.

There are 3 main obstacles. First is matching the odd impedances. The typical TV antenna does have a balanced output before the usual 300 ohm balanced to 75 ohm unbalanced balun, but its characteristic impedance is 300 ohms and I haven't seen any 300 to 110 ohm baluns at Radio Shack lately! You could wind your own if you are handy...

Second problem is noise pickup. In theory a cat-5 twisted pair rejects common mode undesired signals like electrical noise, but that only works well when the receiver has a true balanced input. The good old 300 ohm inputs on TVs went away a long time ago in favor of the 75 ohm unbalanced "F" connector, probably for good reason. So now we need a 2nd custom balun from 110 balanced UTP to 75 ohm unbalanced at the input to the TV.

Finally there is the issue of signal attenuation. Cat-5 cable is usually sweep tested and rated for use at up to 1GHz for digital signals, well above the top end of the UHF band. But it is not measured for attenuation the same way 75 ohm coax like RG-6 and RG-59 is, so we don't know how much loss a high end UHF station might have after a 100 or 200 feet run.

Having said all that, if you are adventurous, live in a fairly strong signal area, are mostly interested in DTV (digital) not analog reception, don't mind getting up on the roof (or in the attic) at the antenna, and don't have a neat or convenient way to run some more coax, it would be easy to test the theory.

Connect one cat-x pair, say blue/white, directly to the antenna wing nut terminals, folding the 3 other pairs back out of the way. Don't use any balun, and try to maintain the "twist" as close as possible to the connection point. At the TV input, use one of those old 300 to 75 baluns that come with the "UHF loop" supplied with the set to "match" the sets RF input. Doing this treats the UTP cat-x as if it were 300 ohm twin-lead, which is not an ideal "match" but for this experimentshould work.

This setup violates all kinds of good engineering practices, but because the DTV signal is very robust and forgiving compared to analog TV, I would expect usable reception from local DTV stations, and possibly from the stronger analog channels, especially VHF. Look at it this way: with DTV it will either work perfectly (excepting multipath issues, which would be the same with a coax lead-in) or not at all. If it doesn't work, it's time to run some more coax!

Have fun and enjoy the hobby side of being an AVSer.

Mike
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post #8 of 9 Old 01-30-2008, 04:39 PM
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Quote:
Originally Posted by kevin g. View Post

Please tell me more about the OTA and Direct w/diplexers. I have been kicking this around and am about to buy an Antenna...just couldn't be sure if it would work. I have Dish, but I'm sure it's the same...Before or after the amp/splitter.? I have 1 diplexer for the dual tuner DVR as it is...will this be aproblem?

With a DTV system that just looks at 1 satellite (101) or even a 3 LNB system, using a diplexer is fine -- the bandwidth utilized goes down to 950MHz. The new 5 LNB systems stack the signals from the LNBs, which has the bandwidth going down to 250MHz. OTA uses 54-213MHz (VHF 2-6 & 7-13) and 470-806MHz (UHF 14-69).

CIAO!

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post #9 of 9 Old 01-30-2008, 04:47 PM
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Originally Posted by bmarr View Post

AV Doogie,

It appears that the MPEG4 signal on the new DirecTV satellite cannot be diplexed (I have tried to diplex before the multiswitch, to no avail), which is a common complaint with the new system. Everytime, you think that you have future-proofed, the future proves you wrong.

Brian

I have a dish system (2 high def recievers) which uses MPEG4 and still use a diplexer for my system to split the signal in at least two locations after the multiswitch. Are these systems so different??? I would call a tech specialist about this or ask the question in the DirecTV section of dbstalk http://www.dbstalk.com/index.php?

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