TV Fool  

Go Back   TV Fool > Over The Air Services > Help With Reception

Notices

Reply
 
Thread Tools
Old 8-May-2015, 4:46 PM   #1
bebo189
Junior Member
 
Join Date: May 2015
Posts: 16
Antenna Suggestion in Charlotte (28214)

Hello all. I’m currently receiving ClearQAM (without a cable package) through TWC. I just found out that they are converting all their channels to digital and encrypting them in the process. In order to avoid losing all the channels I currently have (and to get better signal than the portable OTA antenna I currently have), I want to put an antenna in the attic of our 2 story home (don’t want to get onto the roof!)

I’m looking or antenna recommendations and don’t know if I really need any kind of amplification/amplifier. As you can see in the picture below, there are trees just outside our backyard and across the street. Many of them are taller than our home. Also, elevation-wise, we're probably sitting towards the bottom of the neighborhood, which also probably makes receiving a good signal more difficult.




As far as routing of the antenna signal, the house was built with coax to jacks in almost every room. The coax from each room’s jack routes to a central junction box. Currently, only one of those cables is connected to a source (cable internet). My plan is to route the cable from the antenna in the attic down to the junction box, split it in 2, and route those 2 signals to 2 separate rooms where a TV could be hooked up.


http://www.tvfool.com/?option=com_wr...f1f0ab7c76fca4


Thanks in advance for the help!
bebo189 is offline   Reply With Quote
Old 8-May-2015, 6:28 PM   #2
rickbb
Senior Member
 
Join Date: Dec 2014
Posts: 338
You may be in luck, assuming your pic is oriented with north at the top, your roof line is almost lined up with the directions you will get signals from.

Whatever antenna you get will need to go at one end of the house to aim out the gable end. And you have some strong signals close by, most of the stations in green, (LOS {line of sight}), should be easy to get.

(Note the "should be" attics are iffy.)

Having said that construction details are important. Some roofing and siding material will block signals. Foil backed insulation is also a signal killer.
rickbb is offline   Reply With Quote
Old 8-May-2015, 6:36 PM   #3
bebo189
Junior Member
 
Join Date: May 2015
Posts: 16
Quote:
Originally Posted by rickbb View Post
You may be in luck, assuming your pic is oriented with north at the top, your roof line is almost lined up with the directions you will get signals from.
Yes, the picture is oriented with North at the top.

Quote:
Originally Posted by rickbb View Post
Whatever antenna you get will need to go at one end of the house to aim out the gable end. And you have some strong signals close by, most of the stations in green, (LOS {line of sight}), should be easy to get.

(Note the "should be" attics are iffy.)
That is good to know. The area I had planned to install is at the end near one of the gables.

Quote:
Originally Posted by rickbb View Post
Having said that construction details are important. Some roofing and siding material will block signals. Foil backed insulation is also a signal killer.
I don't believe there is any foil backed insulation in the attic, but I will definitely check out construction materials.
bebo189 is offline   Reply With Quote
Old 8-May-2015, 6:55 PM   #4
ADTech
Antennas Direct Tech Supp
 
Join Date: Jan 2010
Posts: 2,942
Here is the overhead with the green lines denoting the aiming directions.



Now you can see the aiming directions relative to your homes orientation.

Because your home is new construction, do check for radiant barrier in the attic or Tech Shield shingles as some new building codes to have requirements for energy efficiency.
Attached Images
File Type: png Bebo189.png (183.2 KB, 1356 views)
__________________
Antennas Direct Tech Support

For support and recommendations regarding our products, please contact us directly at https://www.antennasdirect.com/customer-service.html

Sorry, I'm not a mod and cannot assist with your site registration.
ADTech is offline   Reply With Quote
Old 8-May-2015, 6:59 PM   #5
bebo189
Junior Member
 
Join Date: May 2015
Posts: 16
Quote:
Originally Posted by ADTech View Post
Here is the overhead with the green lines denoting the aiming directions.



Now you can see the aiming directions relative to your homes orientation.

Because your home is new construction, do check for radiant barrier in the attic or Tech Shield shingles as some new building codes to have requirements for energy efficiency.
Thanks ADTech! I will definitely check out for radiant barrier and Tech Shield shingles. Would an antenna recommendation/suggestion depend on if these two things are present in the attic, or can a specific antenna/general antenna type be suggested?
bebo189 is offline   Reply With Quote
Old 9-May-2015, 7:36 PM   #6
bebo189
Junior Member
 
Join Date: May 2015
Posts: 16
Quote:
Originally Posted by ADTech View Post
Here is the overhead with the green lines denoting the aiming directions.



Now you can see the aiming directions relative to your homes orientation.

Because your home is new construction, do check for radiant barrier in the attic or Tech Shield shingles as some new building codes to have requirements for energy efficiency.
Well, it looks like there is no radiant barrier/shingles.

Any thoughts on a cheap antenna like this?

http://www.amazon.com/GE-24792-Anten...=attic+antenna

I'm assuming this is omnidirectional. Not sure if I need any kind of amplification/amplifier.
bebo189 is offline   Reply With Quote
Old 9-May-2015, 8:55 PM   #7
ADTech
Antennas Direct Tech Supp
 
Join Date: Jan 2010
Posts: 2,942
It is absolutely not an omnidirectional. It's bi-directional on high-VHF (you only have one VHF station), and moderately directional on UHF with a 10-15 dB F/B ratio.

I'd try a 4-bay UHF antenna with its reflectors removed and see if that does the trick. You might have to add a separate VHF element if WTVI gives you problems. It's very strong, so I'd suspect that most UHF antennas will still pick it up okay.

Trees will probably be your biggest problem down the road.
__________________
Antennas Direct Tech Support

For support and recommendations regarding our products, please contact us directly at https://www.antennasdirect.com/customer-service.html

Sorry, I'm not a mod and cannot assist with your site registration.
ADTech is offline   Reply With Quote
Old 9-May-2015, 9:03 PM   #8
bebo189
Junior Member
 
Join Date: May 2015
Posts: 16
Quote:
Originally Posted by ADTech View Post
It is absolutely not an omnidirectional. It's bi-directional on high-VHF (you only have one VHF station), and moderately directional on UHF with a 10-15 dB F/B ratio.

I'd try a 4-bay UHF antenna with its reflectors removed and see if that does the trick. You might have to add a separate VHF element if WTVI gives you problems. It's very strong, so I'd suspect that most UHF antennas will still pick it up okay.

Trees will probably be your biggest problem down the road.
So maybe something like this?

http://www.amazon.com/Xtreme-Signal-...al+UHF+antenna
bebo189 is offline   Reply With Quote
Old 19-Sep-2015, 8:36 PM   #9
bebo189
Junior Member
 
Join Date: May 2015
Posts: 16
Still looking for help

So, I'm still no closer to figuring out the specific type of antenna I should get.

ADTech suggested a 4-Bay antenna with the reflectors removed. I'm not exactly sure what a 4-Bay/Bowtie antenna is and what reflectors are and do. Also, what is a VHF element, and how is one added to an existing antenna?

Am I correct in my assumption that a 4-Bay/Bowtie antenna is a multi-directional (but not omni directional) antenna? Also, does multi-directional mean that the antenna can receive signals from multiple directions at the same time, or multiple directions when moved to those directions?

My concern is that I have signals almost 180 degrees apart. Would a 4-Bay/Bowtie antenna allow my to receive all those signals from the two main directions that are 180 degrees apart? The description for this antenna seems to indicate as much, but I'm not 100% sure. If so, how does it work or how would this be accomplished? Do you aim different bays towards the different directions? What would the tolerance/range in each direction be?

Thanks in advance for the help. I'm a mechanical engineer (not as knowledgeable on electronics/antennas), so I want to understand as best as I can how the antenna I buy will work.
bebo189 is offline   Reply With Quote
Old 20-Sep-2015, 1:23 AM   #10
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,719
What is really interesting is that the green signal lines clear the other buildings in both major directions.



This is a 4-bay antenna:



https://www.antennasdirect.com/store...v-antenna.html
http://www.amazon.com/Antennas-Direc.../dp/B0074H3IU6
http://www.bestbuy.com/site/antennas...&skuId=4875742
http://www.solidsignal.com/pview.asp?p=db4e

The assembly instructions show how the reflector is attached:
https://www.antennasdirect.com/cmss_...L_20130723.pdf

With the reflector, the antenna is directional. For best results, the antenna must be aimed at the transmitter. See the antenna pattern on page 2:
https://www.antennasdirect.com/cmss_files/attachmentlibrary/Technical%20Data%20PDF's/DB4E-TDS.pdf

When the reflector is removed, the antenna becomes bi-directional, with the major lobes of the pattern 180 degrees apart. What you lose is some gain (~3 dB) that the antenna had when it was directional. The bi-directional pattern looks something like this:



Quote:
Also, what is a VHF element, and how is one added to an existing antenna?
There are three TV bands:
VHF-Low, real channels 2-6
VHF-High, real channels 7-13
UHF, real channels 14-51

WTVI PBS, real channel 11 and WSPA CBS, real channel 7, are VHF-High channels. The basic UHF antenna covers 14-51, so another element can be added for VHF-High, if needed. The VHF dipole add-on has more gain on VHF-High than the UHF antenna, and is suitable for strong VHF signals.
https://www.antennasdirect.com/store...tenna-Kit.html
https://www.antennasdirect.com/cmss_..._201402062.pdf

The VHF dipole is bi-directional.

I suggest you try the antenna in the attic without removing the reflector, first aimed at 260 degrees magnetic with a pocket compass not a smart phone compass, with the VHF dipole broadside to 107 degrees magnetic to see how it does. You might need to try different locations in the attic. Then aim it for 115 degrees. You might be happy with 260 without needing to remove the reflector.
Quote:
What would the tolerance/range in each direction be?
High gain antennas have a narrow beamwidth, so the aim is more critical; that's the tradeoff. Beamwidth is measured at the half-power points, 3 dB down.

Attached Images
File Type: jpg bebo189TVFgreenlines.JPG (100.6 KB, 1209 views)
File Type: jpg DB4e.JPG (83.7 KB, 1339 views)
File Type: jpg Bi-directional_1.jpg (55.3 KB, 1345 views)
File Type: jpg CH7 7698patternCU2_2.jpg (100.9 KB, 1230 views)
__________________
If you can not measure it, you can not improve it.
Lord Kelvin, 1883
http://www.megalithia.com/elect/aeri...ttpoorman.html

Last edited by rabbit73; 20-Sep-2015 at 3:05 AM.
rabbit73 is offline   Reply With Quote
Old 21-Sep-2015, 6:06 PM   #11
bebo189
Junior Member
 
Join Date: May 2015
Posts: 16
Rabbit73, thanks so much for all the helpful information. I think I'm starting to understand a little better. Just a few additional questions.

Quote:
Originally Posted by rabbit73 View Post
When the reflector is removed, the antenna becomes bi-directional, with the major lobes of the pattern 180 degrees apart. What you lose is some gain (~3 dB) that the antenna had when it was directional.
Let me take this logic a step further to see if I am understanding this concept correctly. When switching from a directional/multidirectional antenna to an omnidirectional antenna, you sacrifice signal strength for the ability to receive signal in all directions. In other words, the range on an omnidirectional antenna is less than on a directional/multidirectional antenna. That being said, since we've been discussing a 4-bay antenna in this thread, am I correct in saying that it is recommended that I start with that type of antenna over an omnidirectional antenna?

Quote:
Originally Posted by rabbit73 View Post
I suggest you try the antenna in the attic without removing the reflector, first aimed at 260 degrees magnetic with a pocket compass not a smart phone compass, with the VHF dipole broadside to 107 degrees magnetic to see how it does. You might need to try different locations in the attic. Then aim it for 115 degrees. You might be happy with 260 without needing to remove the reflector.

High gain antennas have a narrow beamwidth, so the aim is more critical; that's the tradeoff. Beamwidth is measured at the half-power points, 3 dB down.

Just want to make sure I understand this correctly. A 4-bay antenna with reflector not removed is directional, but may still receive channels in both major directions shown on my map because the antenna pattern has lobes that allow it to receive signal 180 degrees from the aimed direction, just at a lower strength (see image below). Thus, if it worked, I would not need to sacrifice gain in the aimed direction. If, however, it doesn't work, I can try removing the reflector and sacrifice the gain to allow me to get a more symmetric reception pattern. Is all that more or less correct?



In regards to a VHF accessory, I will plan to try without first, and then if necessary, I can purchase one after the fact.

I have one more question. Reading about the antenna you have suggested, I don't see any mention of a pre-amp/amplification. In my case, I do plan
to split the signal in 2 and run it a significant distance (50-100 feet). My first question is if I will need active signal splitting or not. Second, am I OK trying the setup without a pre-amp/amplification or is there a pretty good chance I will need it no matter what. If I will need it, what would be the best way to determine how much amplification I need and the best option for my particular setup.

Thanks again!
bebo189 is offline   Reply With Quote
Old 21-Sep-2015, 7:52 PM   #12
rickbb
Senior Member
 
Join Date: Dec 2014
Posts: 338
I don't think you will need a pre-amp, your signals are strong and the towers so close it may do more harm that good.

But you are putting the antenna in the attic, so it's try and see. I'd try without first.
rickbb is offline   Reply With Quote
Old 23-Sep-2015, 2:58 PM   #13
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,719
Quote:
When switching from a directional/multidirectional antenna to an omnidirectional antenna, you sacrifice signal strength for the ability to receive signal in all directions.
First let me say that the terms "multidirectional" and "omnidirectional" are creations of marketing departments that raise the hopes of a buyer and make him think that their antenna will be able to receive signals from many directions. It also makes it more difficult to help people that have been misled.

There are really only two: directional and bi-directional.

For best results, the antenna should be aimed directly at the transmitter for maximum gain and to reject multipath reflections. It will be possible to receive other signals at a slightly different azimuth within the beamwidth of the antenna at reduced gain.

What I said was to try the 4-bay antenna with the reflector first at 260 to see what you can get. Then rotate the antenna to 115 and see what you can get. At that point you might be able to pick just one direction that will make you happy without needing to remove the reflector. If you aren't happy, then it is time to remove the reflector to make the antenna bi-directional for more tests. I picked 260 because I thought it gave the best selection of the major networks.
Quote:
Just want to make sure I understand this correctly. A 4-bay antenna with reflector not removed is directional, but may still receive channels in both major directions shown on my map because the antenna pattern has lobes that allow it to receive signal 180 degrees from the aimed direction, just at a lower strength (see image below). Thus, if it worked, I would not need to sacrifice gain in the aimed direction. If, however, it doesn't work, I can try removing the reflector and sacrifice the gain to allow me to get a more symmetric reception pattern. Is all that more or less correct?
That is more or less correct, but when the reflector is in place the antenna should be aimed at the weak signals direction so that the rear faces the strong signals direction. If you have strong and weak signals in both directions, you have a problem which requires one of these solutions:

1. Two antennas with an A/B switch to select which antenna you want to use
2. An antenna rotator to aim in different directions; an option with many disadvantages
3. Just be happy with what you can get in one direction
Quote:
I have one more question. Reading about the antenna you have suggested, I don't see any mention of a pre-amp/amplification. In my case, I do plan
to split the signal in 2 and run it a significant distance (50-100 feet). My first question is if I will need active signal splitting or not. Second, am I OK trying the setup without a pre-amp/amplification or is there a pretty good chance I will need it no matter what. If I will need it, what would be the best way to determine how much amplification I need and the best option for my particular setup.
Your tvfool report shows very strong signals, but that is with an antenna outside and in the clear without any trees or other buildings in the way. Because there are so many unknown factors involved, there is no way I can predict your results. As rickbb said, you just have to try it.

I suggest you try the antenna with just one TV that hopefully has a signal strength indicator to help you. If that is OK then add a passive splitter for more than one TV. If the signals are too weak for more than one TV, substitute a distribution amp (active splitter) like the Channel Master 3412 or 3414 for the passive splitter. In rare cases when the attic loss is severe, a preamp at the antenna is needed.

WBTV has a Noise Margin of 67.7 dB. If you add the antenna gain of about 12 dB, that brings you up to 79.7 dB which is Overload territory.



Interpreting Noise Margin in the TV Fool Report
http://www.aa6g.org/DTV/Reception/tvfool_nm.html
__________________
If you can not measure it, you can not improve it.
Lord Kelvin, 1883
http://www.megalithia.com/elect/aeri...ttpoorman.html

Last edited by rabbit73; 23-Sep-2015 at 3:35 PM.
rabbit73 is offline   Reply With Quote
Old 23-Sep-2015, 3:14 PM   #14
bebo189
Junior Member
 
Join Date: May 2015
Posts: 16
Awesome. Thanks so much for the help! Going to purchase a 4-bay and see how things turn out. You may see me back here for more help down the road, but hopefully not.
bebo189 is offline   Reply With Quote
Old 13-Jan-2016, 4:36 PM   #15
bebo189
Junior Member
 
Join Date: May 2015
Posts: 16
OK. Just a follow-up post. I ended up buying a Channel Master CM-4221 antenna. I went ahead and mounted it in my attic and aimed in the directions suggested by rabbit73. The antenna runs approximately 50 feet to a junction box on the 2nd floor which can then route to a TV on the 2nd floor (maybe adds 10 - 20 more feet from the junction box), or a TV on the 1st floor (guessing it adds another 50-60 or so feet from the junction box). Which TV it routes to depends on the connection at the junction box. When I have it connected to the 2nd story TV, I get a TON of channels (20+). When I have it connected to the 1st story TV, I get maybe 8 channels.

My assumption is that the long length to get to the 1st story TV causes the signal strength to attenuate so much that it loses channels. Ultimately, I would like to split the signal from the antenna to go to both TVs. Between the long length to the 1st story TV and wanting to split the signal, I'm guessing I will need to get an amplifier. Wondering if that is accurate, and if so, how to determine the specific amplifier needed for me specific application. Any help would be greatly appreciated.

Thanks,
Jeremy Hansen

Last edited by bebo189; 13-Jan-2016 at 4:41 PM.
bebo189 is offline   Reply With Quote
Old 13-Jan-2016, 7:40 PM   #16
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,719
Quote:
My assumption is that the long length to get to the 1st story TV causes the signal strength to attenuate so much that it loses channels.
That sounds correct. Try a Channel Master 3410 just before the splitter in the junction box. How many splits in the existing splitter? The 3410 has only one output, so an alternative would be a 3412 which is a distribution amp and a 2-way splitter combined.

If you need a 3-way split, you can use a 3412 and a 2-way splitter which would allow more signal to the longest run, and less to nearby TVs. If one of your TVs has a signal strength indicator, you can determine how strong a signal must be for reliable reception.
Attached Images
File Type: jpg Efficient3waysplit2_1.jpg (100.0 KB, 407 views)
__________________
If you can not measure it, you can not improve it.
Lord Kelvin, 1883
http://www.megalithia.com/elect/aeri...ttpoorman.html

Last edited by rabbit73; 13-Jan-2016 at 7:54 PM.
rabbit73 is offline   Reply With Quote
Old 13-Jan-2016, 8:05 PM   #17
shoman94
Senior Member
 
Join Date: Jan 2016
Posts: 138
Quote:
Originally Posted by rabbit73 View Post
That sounds correct. Try a Channel Master 3410 just before the splitter in the junction box. How many splits in the existing splitter? The 3410 has only one output, so an alternative would be a 3412 which is a distribution amp and a 2-way splitter combined.

If you need a 3-way split, you can use a 3412 and a 2-way splitter which would allow more signal to the longest run, and less to nearby TVs. If one of your TVs has a signal strength indicator, you can determine how strong a signal must be for reliable reception.
Or use an Antennas Direct CDA4 which has a 7.5db gain for each output. I've also use the RCA vh140R with great results and available right at Lowe's.
shoman94 is offline   Reply With Quote
Old 13-Jan-2016, 8:32 PM   #18
bebo189
Junior Member
 
Join Date: May 2015
Posts: 16
Quote:
Originally Posted by rabbit73 View Post
That sounds correct. Try a Channel Master 3410 just before the splitter in the junction box. How many splits in the existing splitter? The 3410 has only one output, so an alternative would be a 3412 which is a distribution amp and a 2-way splitter combined.
The junction box doesn't have any splitters currently, so I'd need a 2-way splitter.

Quote:
Originally Posted by rabbit73 View Post
If you need a 3-way split, you can use a 3412 and a 2-way splitter which would allow more signal to the longest run, and less to nearby TVs. If one of your TVs has a signal strength indicator, you can determine how strong a signal must be for reliable reception.
Is the signal coming out of a 2-way splitter coming out of 1 output of the CM3412 weaker than the signal coming directly out of the other output of the CM3412? Is that how you are saying you could balance signal strength between TV with longer run vs TV with shorter run?
bebo189 is offline   Reply With Quote
Old 13-Jan-2016, 8:33 PM   #19
bebo189
Junior Member
 
Join Date: May 2015
Posts: 16
Quote:
Originally Posted by shoman94 View Post
Or use an Antennas Direct CDA4 which has a 7.5db gain for each output. I've also use the RCA vh140R with great results and available right at Lowe's.
What would be the advantage of going with a distribution amp with a 4 way splitter if I only need 2 outputs?
bebo189 is offline   Reply With Quote
Old 13-Jan-2016, 8:40 PM   #20
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,719
Quote:
Is the signal coming out of a 2-way splitter coming out of 1 output of the CM3412 weaker than the signal coming directly out of the other output of the CM3412? Is that how you are saying you could balance signal strength between TV with longer run vs TV with shorter run?
Sorry, I have confused you with too much information. That would only be for a 3-way split. For the 2-way split, both outputs of the 3412 are equal.
__________________
If you can not measure it, you can not improve it.
Lord Kelvin, 1883
http://www.megalithia.com/elect/aeri...ttpoorman.html
rabbit73 is offline   Reply With Quote
Reply

Bookmarks

Go Back   TV Fool > Over The Air Services > Help With Reception


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off




All times are GMT. The time now is 2:17 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Copyright © TV Fool, LLC