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Old 21-Jan-2010, 3:17 PM   #1
FolFool
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Can I really use a set-top antenna?

My HD TV won't be arriving until next week, but I was hoping to have an antenna ready to try out once it arrives.

Here's my tvfool data:
http://www.tvfool.com/?option=com_wr...c5720b1f587ed1

All the stations I care about are located in the green ("set-top") section, within a band that's just 3 degrees wide (214-217).

I do NOT want to roof-mount (tile roof, association, etc.). I'm in an 8-year old home with a wiring distribution system that goes into a CM splitter/combiner in a box in a closet. I noticed there's what looks to me to be a spare CAT 5 cable run in the attic, so I'm hoping if I install an antenna there and hook it up to the cabling I can just change the input in the combiner and, voila, Comcast out, OTA in. We will eventually have 3 HD TVs connected, but there are at least 2x that many coax connector jacks (?) throughout the house.

So if I can really use a set-top antenna to get those stations (including 2 in the Hi-VHF area), is it unreasonable to hope that an attic antenna would also work?

Bottom line: What antenna would you recommend I try? And do I need a pre-amp as well (I'd estimate the attic cable run to the distribution box to be 75 feet or more).

Thanks in advance!
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Old 21-Jan-2010, 6:29 PM   #2
mtownsend
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Hello and welcome!

Quote:
Originally Posted by FolFool View Post
I'm in an 8-year old home with a wiring distribution system that goes into a CM splitter/combiner in a box in a closet.
Does this splitter have any amplification? When a signal feed is split, less power will go down each branch of the split. It sounds like this is a 4-way or 8-way splitter.



Quote:
I noticed there's what looks to me to be a spare CAT 5 cable run in the attic, so I'm hoping if I install an antenna there and hook it up to the cabling I can just change the input in the combiner and, voila, Comcast out, OTA in.
Are you suggesting to connect the antenna to the CAT 5 cable? Just so you know, this will not work very well. The impedance mismatch between the different systems will cause lots of signal loss. You need to keep the OTA signal in its native 75 ohm coax, preferably RG6.



Quote:
We will eventually have 3 HD TVs connected, but there are at least 2x that many coax connector jacks (?) throughout the house.
That is fine as long as you terminate the unused ports (inexpensive F-type terminators are available for this). This will prevent any open-ended ports from "reflecting" the signal back into the coax and potentially causing self-interference problems.



Quote:
So if I can really use a set-top antenna to get those stations (including 2 in the Hi-VHF area), is it unreasonable to hope that an attic antenna would also work?
I think an attic installation would work best. If you use an antenna like the Antennacraft HBU-22, it will adequately handle channels 7-69. Since it is significantly better than your average set-top antenna (but probably still in the same price range), it should be able to provide enough extra signal to overcome the loss of your long coax run. The added directionality of the HBU-22 over a set-top antenna can also reduce the impact of multipath (signal reflections from the environment that can make channel decoding more difficult). This will improve your chances of getting a clean signal to your TV that is easy to lock on to.

I would avoid using any pre-amp for now. Your signals are strong, so a pre-amp would be at risk of being overloaded if installed right after the antenna.

If your distribution splitter has a built-in amp, I would leave that in for now. The line loss between the antenna and the distribution splitter might be enough to bring the power down to a level that can be handled by the amp without overload. If we discover signs of amp overload, we can discuss ways to disable or bypass the amp later.

If the distribution splitter does not have an amp, then we'll just leave it that way. Your OTA signals are probably strong enough to drive a clean signal to each TV despite the multiple splits. Again, I'd try the most straightforward thing first, and if adjustments are needed, we can deal with those later.
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Old 21-Jan-2010, 7:12 PM   #3
FolFool
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Quote:
Originally Posted by mtownsend View Post
Does this splitter have any amplification? When a signal feed is split, less power will go down each branch of the split. It sounds like this is a 4-way or 8-way splitter.
It's a 4-way splitter (ChannelPlus, by the way, not CM -- not that it matters). I just looked, and I can't find any amplification, though I'd swear I remember the Comcast guy talking about adding one when it was originally installed. I must be mistaken, though.

Quote:
Are you suggesting to connect the antenna to the CAT 5 cable? Just so you know, this will not work very well. The impedance mismatch between the different systems will cause lots of signal loss. You need to keep the OTA signal in its native 75 ohm coax, preferably RG6.
Yeah, that was pretty silly of me! Sorry. The distribution box has both CAT5 and RG6 cables in them, and I just looked at the wrong one and wrote it down. Brain freeze. But I don't know which is in the attic. I would hope and assume it's RG6. If it's not, then I guess I need to find a way to drop an RG6 cable down from the antenna into the box. Gulp. Hopefully it won't come to that.



Quote:
I think an attic installation would work best. If you use an antenna like the Antennacraft HBU-22, it will adequately handle channels 7-69. Since it is significantly better than your average set-top antenna (but probably still in the same price range), it should be able to provide enough extra signal to overcome the loss of your long coax run.
That one looks fine. I will give it a try.

Thank you so much; I really appreciate your help. I will come back in a few weeks and post my results (unless I have questions even before I get that far).

Thanks again!
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Old 21-Jan-2010, 8:33 PM   #4
mtownsend
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Quote:
Originally Posted by FolFool View Post
That one looks fine. I will give it a try.

Thank you so much; I really appreciate your help. I will come back in a few weeks and post my results (unless I have questions even before I get that far).

Thanks again!
You're very welcome, and good luck.

BTW, the Antennacraft HBU-xx antennas can be found at most Radio Shack stores in case you're looking for a convenient return option. It's probably a little cheaper from online retailers (especially if you plan on purchasing coax, connectors, mounts, masts, and other components at the same time), but be sure to factor in shipping costs when comparing prices.
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Old 21-Jan-2010, 11:25 PM   #5
FolFool
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Thanks, I like the idea of getting it from our local Radio Shack, in case it doesn't work out.

I just looked at the assembly instructions. I'm not thrilled with this quote: "Once the elements are locked into position, do not attempt to unlock them. Doing so might break the elements." How do they expect someone to return it after trying it out if it can't be folded back? I'm not even sure I can get it out of the attic once it's opened up (better not open it until I'm up there!).

Drat, my local RS store doesn't carry it. I'll need to get it shipped there. Oh, well, no big deal.

I don't have a clue how I'll mount this yet. First I need to make sure it will even fit up there (I believe it will, but it's pretty tight between vertical beams -- about 2 feet).

This is fun; feels like the 1960s.
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Old 22-Jan-2010, 4:46 AM   #6
mtownsend
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Quote:
Originally Posted by FolFool View Post
I don't have a clue how I'll mount this yet. First I need to make sure it will even fit up there (I believe it will, but it's pretty tight between vertical beams -- about 2 feet).
There are some simple mounting brackets that can be used to hold a short mast (either hanging from above, or coming up from the bottom).


The antenna itself is designed to clamp onto a vertical mast (just about any pipe up to 1.5 inches in diameter will do). This will hold the antenna in mid-air so that it doesn't come into direct contact with anything else.
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Old 22-Jan-2010, 4:51 AM   #7
FolFool
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Hey, great, that looks perfect! I can just screw that into an overhead beam and hang a short pipe down -- simple as can be.

Thanks again!
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Old 23-Jan-2010, 3:02 AM   #8
FolFool
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One more quick question, as RS doesn't seem to have shipped the antenna to their store yet:

After some research, I found that my fear was accurate. Once unfolded, it's "impossible" (to quote someone I read) to "re-fold" the elements without damaging the antenna.

So: Can I test the antenna without completely unfolding the elements? If not, is there an acceptable alternative to the HBU-22 you could recommend that might not have this design?

Sorry to keep bugging you, but that's what can happen when you're so generous and responsive.
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Old 23-Jan-2010, 7:33 AM   #9
mtownsend
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Quote:
Originally Posted by FolFool View Post
After some research, I found that my fear was accurate. Once unfolded, it's "impossible" (to quote someone I read) to "re-fold" the elements without damaging the antenna.
I'd ask the RS salesman if it would be OK to return an antenna (even if it's been unfolded) if it doesn't work out. I think it's a completely reasonable request to try out an antenna as it was originally designed and still have the option of returning it if it doesn't work out.

I have a feeling that the answer you get will depend on who you're asking, but I hope that for the sake of RS's image/reputation, they will say that it's OK. Returns are one of the reasons RS still has decent business. Without that differentiation, everyone would just go online and buy stuff for less.



Quote:
Can I test the antenna without completely unfolding the elements?
Maybe, but it's hard to say how close you can get to its final position without accidentally popping it into its "permanent" position. If the elements are not that close to their intended spacing, the antenna performance will not be as good as it should be.



Quote:
If not, is there an acceptable alternative to the HBU-22 you could recommend that might not have this design?
All the combo antennas have a "snap into position" design so that they can pack and ship "large" antennas in a relatively small package. Each model has their own mix of plastic or aluminum "catches" that hold the elements in their intended position. Sometimes they are easy to undo and sometimes they are not. I have not looked that closely at the HBU-22 yet to see how "permanent" they made their design. I might take a look at one over the weekend to get a better sense.

I know that some of the Winegard latches are also hard to undo. They're not completely impossible, but very tough to undo by hand (the right hand tools and/or friends helping out can make things a little easier).

I couldn't say off hand which antenna would be the easiest to uninstall (haven't had to return any yet, knock on wood). The only times I've had to take down an antenna was due to storm damage or age related replacement.



Quote:
Sorry to keep bugging you, but that's what can happen when you're so generous and responsive.
That's why we're here!

And who knows, maybe someday, your experience will be valuable to others too! Actually, there are probably people reading this right now that are already learning something from your saga. That's the wonderful thing about having a forum to discuss these things.
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Old 23-Jan-2010, 5:15 PM   #10
FolFool
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Thanks, that's great advice. I'll be sure to ask RS if I can return it once unfolded. Maybe they'll know a trick to re-fold it.

But I suppose I should look on the positive side of things -- it will work great, and there won't be any need to return it.

I got an email late last night from RS that it was shipped and should arrive at my local RS on Wednesday. So hopefully by the end of next week, I'll know.

Thanks again -- it'd be great if this helps someone else, but in the meantime, it really has helped me!
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Old 28-Jan-2010, 4:54 AM   #11
FolFool
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Success!

I don't have the antenna mounted yet, but simply placing it on the floor of the attic and connecting the cable directly to the TV, I was able to get an "average" or better signal on ALL the channels I wanted to!!!! A very good feeling!

When holding it up in the air, all channels were "good" or better, but I don't know if my holding it affects the results (as opposed to the antenna just being mounted there). But I'll find out soon enough, when I do mount it.

Also, I couldn't connect it directly to the wiring distribution system because I discovered the end of the wire up there didn't have a connector, and I didn't have any around. But I fooled around with the distribution box connections a bit, and I'm now confident I can do what I want. I also ran a very long cable from the antenna to the distribution box and tried it that way. Lost quite a bit of signal doing that, though, and even an old amplifier I had around didn't help*. The bundle of wire up in the attic is pretty large (easily 50 unneeded feet), so worst case I can cut off the excess if I have to. I think it's going to all go together great.

Thank you so much, mtownsend, for all your help! I'm ecstatic!

*Edited: It DOES help considerably, if it is inserted in the correct location. I realized after writing this that it makes the most sense to connect the amplifier to the antenna, rather than in the distribution box. That boosted signals one notch (average became good, poor became average, etc.). I still may not need it once the antenna is properly installed, but it's good to know I have the option if necessary. It's an old Radio Shack 15-1113A amp, up to 25dB (variable gain).

Last edited by FolFool; 28-Jan-2010 at 4:42 PM.
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Old 28-Jan-2010, 6:58 AM   #12
mtownsend
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Sounds fantastic. Congratulations!
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