or Connect
AVS › AVS Forum › HDTV › HDTV Technical › Houston, TX - VHF issues with attic install
New Posts  All Forums:Forum Nav:

Houston, TX - VHF issues with attic install

post #1 of 23
Thread Starter 
I installed an Antennacraft U-4000 in my attic recently for OTA reception throughout my whole house. The antenna height is roughly 21-25' above the ground, with no major obstructions towards the nearest station antenna cluster. The antenna is unamplified and run into a 1 to 8 splitter in my equipment closet (says 12 dB on all the outputs, but is not powered - I'm not sure if it's a passive amp or not). The splitter puts the cable all around the house. I have an iView OTA DVR box upstairs and the built-in tuner on my Panasonic TH58PX600U plasma downstairs. They both agree with signal quality levels, so the tuners appear to be fine.

The issue: My UHF reception is great, with most channels at 100% strength, and the weaker ones at ~70-80% strength. My VHF pretty much sucks.


Here's what I'm working with:

Radar-All.png

The main VHF channels I want are KHOU (ch 11) and KTRK (ch 13). I was thinking the U-4000 had enough gain in the upper VHF to get me those channels, but it appears not. I'm at about 20-25% strength on KHOU and 0-10% on KTRK (can't even get a pic).


This is a pic of the U-4000 install, complete with some poor TIG welding of a mounting bracket on the bottom. The antenna is pointing at ~116-118 deg at the front of my attic, about 21-25' AGL. One of my potential issues is the tech shield (foil barrier on plywood roof decking). I aimed the antenna to get the best shot out of a ~6' x 4' pitch that has no tech shield on it. Unfortunately that's smaller than most VHF wavelengths, which might explain some problems. The only other option is to move the antenna back to the back of my attic about 14-18' AGL. This would have it well below the tech shield, but it'd be going through all of the 2nd story of my house to get line of sight to the towers. That would put another 50' run of RG-6 in between the antenna and splitter (25' now). I don't think an amplifier on the antenna is going to get me anything here correct?

e2as.jpg



So my question - what sort of VHF antenna do I need to pull in these two stations? I don't need 100% signal strength, but something in the 50-70% range to get watchable TV is the minimum. Will a set of VHF rabbit ears work? How would I install that in the circuit? Do I need a reverse splitter/signal combiner?


Hopefully that's enough detail without going overboard. Thanks for any help guys!
post #2 of 23
Good Day from the other side of Texas. You need to use a UHF/VHF signal combiner such as this http://www.solidsignal.com/pview.asp?p=uvsj&d=pico-macom-uvsj-uhf-vhf-band-separator/combiner-for-antenna-(uvsj) to combine your UHF antenna with any added VHF antenna so that only UHF is picked up from the UHF antenna and VHF from it's counterpart. Yes, you could start with a simple rabbitear for the VHF. Extend the rods only about 12 inches on each side and position them horizontally broadside to your station's towers. You obviously prefer an attic installation over outdoors, but is there anyway you could sneak those rabbit ears outside under an overhang or something? I envy your abundance of channels available in Houston.
post #3 of 23
Thread Starter 
Howdy fellow Texan!

Do you think some cheap rabbit ears will bring in those two channels? The signal strength from TVFool makes me think perhaps. I was a bit nervous with the UHF stuff, and maybe went a bit overkill there, but the U-4000 wasn't too expensive. But I don't know what's going with the splitter installed in the equipment box. The signal strength is really strong in the UHF band, so I'm thinking it can't be hurting things much.

Unfortunately an attic install is a must, but I can't say I'd want to see a pair of rabbit ears sticking out on the roof either.

I'll squeeze over there and put the VHF antenna right by the apeture the pitch makes there. That should help some with the Tech Shield issue.
post #4 of 23
You're killing the receive signal with an 1 to 8 splitter, that's not a 12dB gain, but a -12dB loss at each port. Before doing anything else I would do a simple test by temporarily bypassing the splitter and couple the antenna feed into a feed that runs directly to on of your TV's. If you suddenly notice your VHF channels start working, then you will need to get an amplifier. The tvfool post shows the signal levels should be pretty good even with the -12dB loss from the splitter, but I always like to do these simple test before anything else.
post #5 of 23
You really need to get the antenna out of that Tech Shield enclosed attic. A small antenna like an RCA ANT751R or a ClearStream 2V is unobtrusive and is all you need.

If your concerns are due to an HOA or neighborhood restrictions, they can go pound sand as such restrictions are generally illegal under federal law. See http://www.fcc.gov/guides/installing-consumer-owned-antennas-and-satellite-dishes
post #6 of 23
Quote:
Originally Posted by RPS13 View Post

Howdy fellow Texan!

Do you think some cheap rabbit ears will bring in those two channels? The signal strength from TVFool makes me think perhaps. I was a bit nervous with the UHF stuff, and maybe went a bit overkill there, but the U-4000 wasn't too expensive. But I don't know what's going with the splitter installed in the equipment box. The signal strength is really strong in the UHF band, so I'm thinking it can't be hurting things much.

Unfortunately an attic install is a must, but I can't say I'd want to see a pair of rabbit ears sticking out on the roof either.

I'll squeeze over there and put the VHF antenna right by the apeture the pitch makes there. That should help some with the Tech Shield issue.

I certainly believe rabbit ears would do the job is they were outside. You could even try a FM antenna like this http://www.radioshack.com/family/index.jsp?categoryId=2032204&allCount=32&s=D-StorePrice-RSK&s=D-StorePrice-RSK&fbc=1&f=PAD%2FProduct+Type%2FFM+only&fbn=Type%2FFM+only&filterName=Type&filterValue=FM+only along the roof line or in some other way that it would not be seen from the ground. Alternatively, you could make up a similar product with the suggested length of abut 12 inches on each side of the dipole, out of old fashioned 300 ohm lead-in wire. Of course, the experiment suggested of removing the splitter temporarily is of value, but I would be hesitant to use any amplification in such a strong signal area.
post #7 of 23
Thread Starter 
Quote:
Originally Posted by bac522 View Post

You're killing the receive signal with an 1 to 8 splitter, that's not a 12dB gain, but a -12dB loss at each port. Before doing anything else I would do a simple test by temporarily bypassing the splitter and couple the antenna feed into a feed that runs directly to on of your TV's. If you suddenly notice your VHF channels start working, then you will need to get an amplifier. The tvfool post shows the signal levels should be pretty good even with the -12dB loss from the splitter, but I always like to do these simple test before anything else.

That makes sense. It would be nice to keep the signal going all throughout the house via the same splitter. I did buy a 1 to 3 passive splitter in case it was an issue, as I do currently need 3 ports fired up. I might try that and see what the result is, but I doubt that'll get the 0-10% signal strength channel to come in. Most UHF channels are super strong, so I do worry a bit about adding an amplifier.
post #8 of 23
Thread Starter 
Quote:
Originally Posted by ProjectSHO89 View Post

You really need to get the antenna out of that Tech Shield enclosed attic. A small antenna like an RCA ANT751R or a ClearStream 2V is unobtrusive and is all you need.

If your concerns are due to an HOA or neighborhood restrictions, they can go pound sand as such restrictions are generally illegal under federal law. See http://www.fcc.gov/guides/installing-consumer-owned-antennas-and-satellite-dishes

No antenna is going outside unless absolutely necessary, and even then it'd be very stealth. But I'm not so sure I want to climb 25' up in the air on a ladder for "free" TV. It doesn't really matter what the federal law is or the HOA rules (they do forbid visible dishes/ antennas, people do it anyway with dishes on occasion), as I wouldn't really want someone sticking a big VHF antenna on their roof next to me, so I'll live by the golden rule even if I just need a small antenna.

I'll see how it goes with the rabbit ears, as I have a feeling I just need a little nudge to bring things up. The U-4000 is more than I need in the UHF spectrum, so it's not like the install is causing problems now.
Quote:
Originally Posted by Mister B View Post

I certainly believe rabbit ears would do the job is they were outside. You could even try a FM antenna like this http://www.radioshack.com/family/index.jsp?categoryId=2032204&allCount=32&s=D-StorePrice-RSK&s=D-StorePrice-RSK&fbc=1&f=PAD%2FProduct+Type%2FFM+only&fbn=Type%2FFM+only&filterName=Type&filterValue=FM+only along the roof line or in some other way that it would not be seen from the ground. Alternatively, you could make up a similar product with the suggested length of abut 12 inches on each side of the dipole, out of old fashioned 300 ohm lead-in wire. Of course, the experiment suggested of removing the splitter temporarily is of value, but I would be hesitant to use any amplification in such a strong signal area.

Hmmmm... I still don't see how just moving the rabbit ears 5" further out is going to make a big difference, but I deal with physical things on a daily basis, not this witchcraft ether electrical stuff. smile.gif


Maybe I'm just annoyed that this "free" OTA TV project is starting to exceed the "exceedingly non-trivial" level, but the UHF/VHF combiner is a bit pricey for a few caps and inductors. Could I just get one of those cheap UHF/VHF indoor antennas with rabbit ears on it, and gut the thing to use its combiner? Or does it likely not have one since it's so low performance? Would a cheap splitter really kill the signals?
post #9 of 23
FWIW... I had some rabbit ears in my "junk box" that had 300 Ohm twinlead. Similar to this:

http://www.ebay.com/itm/like/290806992874?lpid=82

I just connected the twinlead to the existing balun connector of the UHF antenna without a joiner/combiner. Works like charm in my attic for channels 6 and 12.
post #10 of 23
Just an FYI, your HOA can get bent about dishes/antennas that transmit either internet or video broadcast. I just helped a co-worker fight his HOA over his line of sight internet service(15mbps). The HOA said he could only use dial up(he lives out in a acreage community) and was threatening to start fining him $500 every day he had the antenna up. I found him the following link and he emailed it to the HOA. He hasn't heard from them sense.

http://www.fcc.gov/guides/over-air-reception-devices-rule
post #11 of 23
A cheap splitter used backwards will let the VHF that you are currently getting from the UHF antenna mix with the VHF from a dedicated antenna. It usually reduces the signal rather than add them together. It may work in isolated instances. You could also just replace your current antenna with this http://www.radioshack.com/product/index.jsp?productId=2103077&znt_campaign=Category_CMS&znt_source=CAT&znt_medium=RSCOM&znt_content=CT2032189 budget indoor antenna. It is often recommended due to it larger than normal UHF loop. There is combiner circuitry inside of it as I have opened mine up. I suppose you have to realize that those of us who frequent this section of our forum usually prefer to do things the most technically proper way possible and personally I find large outdoor antennas to be a thing of beauty. To each his own.
post #12 of 23
Thread Starter 
I understand it might be blasphemy to look for a little bit of a cheaper way out, but I get my kicks doing other things via ridiculous overkill - just not TV antennas. It's all in how you get your jollys. smile.gif

I like the current UHF reception, so I'll keep the current antenna. I did find a UHF/VHF combiner for just $6 shipped which seems more reasonable, so that's covered.

I'll toss in a set of rabbit ears and see how she fares. If the reception still sucks then I'll start thinking about something more drastic.


Thanks for the help guys - I appreciate you being kind even with my obvious n00bness here.
post #13 of 23
Thread Starter 
So I decided that since I want to keep the 1 to 8 splitter, I would get a preamp that could combine UHF/VHF signals. While I'm sure not the nicest one out there, I got an RCA TVPRAMP1R and two cheap rabbit ears for VHF. Maybe I'll frankenstein up both the rabbit ears joined together if one doesn't work. cool.gif I figure the amp should be fine after dropping 12 dB through the splitter.

I'm thinking this will give me enough to get the strong stations in my area.
post #14 of 23
Try turning the UHF antenna that you have up there about 45 to 60 degrees off-axis from the direction of the VHF stations, and see if they come in fair. A UHF antenna like what you have is going to pick up VHF at very weird angles. This will tell you (as a test) if there is any useable VHF signal in the attic.
If your attic has metallic shielding (foil or whatever), you're going to have problems with reception inside.
Also, most indoor electronic "toys" give off a lot of interference at VHF frequencies....having foil insulation just blocks the desired signal, and makes the interference worse.
post #15 of 23
I added rabbit ears to a UHF antenna in the attic with a UVSJ and got strong results for my VHF channels, even a problematic RF13. All connected to a preamp with no overload. You may also want to try a distribution amp in place of the splitter. The Channel Master models are good, and they have 2, 4, and 8 port versions. And there is also an Antennacraft 7-13 antenna if stronger HiVHF performance is needed.
post #16 of 23
Thread Starter 
That's why I went with the RCA amplifier - so I can continue to use the 1 to 8 splitter in my equipment cabinet and hopefully get a nice, strong signal. The RCA amp can supposedly combine just that spectrum of each signal, or you can hook up two full spectrum antennas to it to combine the full spectrum. Seemed like a reasonable way to spend $24 when it was looking to be roughly $7-8 just for the UVSJ, and hopefully fight some of the signal loss of the splitter.

I should have everything up and going this weekend.
post #17 of 23
RPS13:

I'd consider adding an Antennacraft Y5-7-13 VHF-high antenna and a UVSJ (or your dual-input amp) in your attic. The U4000 is designed to resonate only on UHF, with little to no gain on VHF-high. Just make sure to locate the antennas so neither "aims through" the other, and you should be fine.
post #18 of 23
Quote:
or you can hook up two full spectrum antennas to it to combine the full spectrum.

No you can't. You can either hook up the two separate-band antennas (SEPARATE) or you can hook up a single multi-band antenna (COMBINED).

There are no pre-amps that are set up to combine two multi-band antennas.
post #19 of 23
The RCA preamp has 2 separate inputs for UHF and VHF. So you can connect a UHF antenna and a VHF antenna without interference. Just be sure the splitter or the junction box does not block the power supply. Must allow for DC power pass.
post #20 of 23
Thread Starter 
Quote:
Originally Posted by ADTech View Post

No you can't. You can either hook up the two separate-band antennas (SEPARATE) or you can hook up a single multi-band antenna (COMBINED).

There are no pre-amps that are set up to combine two multi-band antennas.

I got it last night, and this is correct. Some previous information I saw incorrectly listed you as being able to pass 2 full spectrum antenna signals through each input (they even posted a picture of this setup!). It becomes very clear when you look at the labelling of the inputs.


I'll toss the stuff up in the attic today and see how it performs. I have quite a few power outlets in the attic so I could power the power inserter up there if the splitter doesn't pass power.



Speaking of that - the RCA preamp doesn't seem to have any sort of indication it's on and functioning. I guess I can unplug the inserter and see if things get bad or is there any other way to tell if the preamp is working.
post #21 of 23
Quote:
I guess I can unplug the inserter and see if things get bad or is there any other way to tell if the preamp is working.

That's about all you can do. While I haven't checked that particular amp, my general observation is that unpowered amps turn into ~30 dB attenuators and you'll loose any weaker station that doesn't have enough power to overcome the new attenuation.
post #22 of 23
Thread Starter 
Just to update this thread - tossed a set of super cheap rabbit ears ($4 shipped for TWO sets! hah) up in the attic and the RCA preamp.

All VHF channels where the antenna is pointed now come in at 100% signal strength, as well as all UHF channels are now 100%. So I guess the preamp was money well spent when going through the -11 dB 1 to 8 splitter.


So mission accomplished - makes sense an amp and a moderate antenna get me what I needed when it's up in the attic.


Thanks for all the help guys.
post #23 of 23
Quote:
Originally Posted by RPS13 View Post

Just to update this thread - tossed a set of super cheap rabbit ears ($4 shipped for TWO sets! hah) up in the attic and the RCA preamp.

All VHF channels where the antenna is pointed now come in at 100% signal strength, as well as all UHF channels are now 100%. So I guess the preamp was money well spent when going through the -11 dB 1 to 8 splitter.


So mission accomplished - makes sense an amp and a moderate antenna get me what I needed when it's up in the attic.


Thanks for all the help guys.
Glad to hear the rabbit ears and amp worked. Like I said, I have a basic set of rabbit ears connected to an amp in the attic, and they work great receiving all of my VHF channels, including one problematic RF13. And I also have a separate UHF antenna for local and distant channels. Using a proper set up will often provide good results, rather than some junk or gimmick antenna that will not.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: HDTV Technical
AVS › AVS Forum › HDTV › HDTV Technical › Houston, TX - VHF issues with attic install