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.


http://i60.tinypic.com/20fbvrn.jpg

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!

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.

Yes, the picture is oriented with North at the top.

That is good to know. The area I had planned to install is at the end near one of the gables.

I don't believe there is any foil backed insulation in the attic, but I will definitely check out construction materials.

Here is the overhead with the green lines denoting the aiming directions.

http://forum.tvfool.com/attachment.p...1&d=1431111187

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?

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.

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

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.

What is really interesting is that the green signal lines clear the other buildings in both major directions.

http://forum.tvfool.com/attachment.p...6&d=1442712107

This is a 4-bay antenna:

http://forum.tvfool.com/attachment.p...7&d=1442712146

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:

http://forum.tvfool.com/attachment.p...9&d=1442715947

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.
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.

http://forum.tvfool.com/attachment.p...2&d=1442718008

Rabbit73, thanks so much for all the helpful information. I think I'm starting to understand a little better. Just a few additional questions.

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?

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?

http://i.imgur.com/ApF9X3u.jpg

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!

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.

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.
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
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.

http://forum.tvfool.com/attachment.p...2&d=1441462888

Interpreting Noise Margin in the TV Fool Report
http://www.aa6g.org/DTV/Reception/tvfool_nm.html

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.

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

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.

The junction box doesn't have any splitters currently, so I'd need a 2-way splitter.

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?

What would be the advantage of going with a distribution amp with a 4 way splitter if I only need 2 outputs?

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.

Future... If you ever decide to add a TV and it's 7.5db gain on each output.

Actually, it's ~15 dB gain with ~7-8 dB insertion loss per port. The net gain is around 7.5 dB for a typical four-port distribution amp with a 15-16 dB amp at its input.

All consumer distribution amps with multiple outputs follow the same scheme. One amp, followed by no splitter, a two-port, a four-port, eight-port, etc. Each time the signal is split in half, an insertion loss of 3.5-4 dB is incurred.

Your site specifically states 7.5db gain per port. I guess I was misinformed.

Not misinformed, just under-informed. ;)

Things on the website are often greatly simplified....

"7.5 dB Gain per port"

So when I read this it doesn't mean what it says?:confused::confused::confused:

It means what it says, but it is a simplification.

Using the Channel Master series as another example for comparison of specs:

3410
A one port distribution amp does not contain a splitter, so its gain is 15 dB.
http://www.channelmaster.com/Antenna..._p/cm-3410.htm

3412
A 2-port distribution amp contains an amp with a gain of 15 dB and a 2-way splitter with a loss of 3.5 dB per port, for a NET gain of 11.5 dB per port.
http://www.channelmaster.com/Antenna..._p/cm-3412.htm

3414
A 4-port distribution amp contains an amp with a gain of 15 dB and a 4-way splitter with a loss of 7 dB per port, for a NET gain of 8 dB per port.
http://www.channelmaster.com/Antenna..._p/cm-3414.htm

Just to male it even more confusing, PCT International not only makes the CM distribution amps with the stupid hard-to-read black labels, they also make the mini drop passive return CATV amps with white labels that are equivalent.
http://www.pctstore.com/RF_Amplifier...fiers_s/58.htm

OK, bought the CM3412 and hooked up one of the outputs to the TV upstairs and then switched it to the TV downstairs. It added a few more channels (33 total, up from 21 or so) to the upstairs TV. It also added a few more to the TV downstairs (18 total up from 8 or so). I'm wondering why there could still be such a discrepancy. Is it possible that some of the cabling being used on the downstairs route is not up to snuff? Any ideas?

Which direction did you pick for the 4221, 260 or 115?

Where is the 3412 located, near the antenna or further downstream?

Tell us how long the cable runs are starting at the antenna, then down to the splitter or 3412, then to each TV. Is it like this?

Give us a list of channels at each TV; it does sound like the 3412 made an improvement.

Yes. It is also possible that there is a hidden splitter or defect on that run. You can check that by running a temporary length of known good coax downstairs.

Do you have any way to measure the signal strength with one of your TVs?

I tried 260 first, then 115 (current direction and the setup used to pickup # of channels listed in my previous post).

3412 is right off of the antenna (maybe 6 feet of cable away at most).

Very similar, I'd say it's closer to this:

Note: Up to this point, I have not had both 3412 outputs hooked up to both paths. I have been switching between paths where the coax 50 ft enters the junction box. After I verify that I can get all the channels I want on the downstairs TV, I plan to run the extra 50 ft coax and truly split the signal to both paths.

Also, is it possible that the 25 feet of coax cable that I run through the wall on the 1st floor to the TV would degrade the signal if it weren't 75 ohm quad shielded? I read somewhere that this was important. I bought this years ago, and I'm not sure if it is 75 ohm quad shielded or not.

I will pull the list when I get home for both TVs.

I tried looking for this option on my 1st floor TV, but couldn't find anything after experimenting or googling the TV. My TVs are listed below. Maybe someone can help me locate a way to check it.

• Vizio M552I-B2 (1st floor TV)
• LG 42LD550 (2nd floor TV)

Here's the channels I get on each of the TVs. Each TV has it's own tab. On the 2nd floor TV, the channels highlighted in green are ones that the 1st floor TV doesn't pick up.

50 + 20 + 6 = 76 ft
50 + 60 + 25 = 135 ft
difference of 59 ft; about 3 dB for UHF,
approx. the same as a 2-way splitter loss

So if you inserted a 2-way splitter in the 2nd floor line after the 3412, the 2 TVs should be getting about the same signal strength. If not, there is another loss that exists in the 1st Floor line.
The attenuation loss is about the same for regular coax as it is for quad. The quad has an extra layer of shield to reduce pickup of interference; you don't need it for most applications.

Do you have AC power for the 3412 in the attic?

LG 42LD550
http://www.lg.com/us/support-product/lg-42LD550
When selecting DTV or Cable DTV input signal in Manual Tuning, you can view the on-screen signal strength monitor to see the quality of the signal being received.

http://forum.tvfool.com/attachment.p...4&d=1453348228

I'm having trouble downloading your Google doc of channels. I think I would need to log on before it would allow my me to download it; I have had this trouble before.

OK, got your 1st Floor list using View Only at Google Docs. A lot of signals coming in the back of the antenna.

http://forum.tvfool.com/attachment.p...5&d=1453422015

And the 2nd Floor
http://www.rabbitears.info/search.ph...pe=dBm&height=
click on callsign to see networks

http://forum.tvfool.com/attachment.p...6&d=1453426856

Sorry, it's taken me so long to respond.

Yes, I have the 3412 plugged into an outlet in the attic using the AC adapter that came with the 3412. The AC adapter is connected to the unit via a coax cable.

I went ahead and used the instructions you posted to get the signal strength/signal quality readings for each channel on the LG 42LD550 (2nd Story TV). Here they are:

http://forum.tvfool.com/attachment.p...3&d=1453771288

Reminder: Green is channels I get on the 2nd Floor TV but not on the 1st Floor TV. Bolded Channels are the ones that I actually WANT to get on both TVs.

I am not sure what the difference is between "Signal Strength" and "Signal Qualtiy" as called out on my LG 42LD550 TV.

Also, the weird thing to me is that is that the main channels that I want to get on the 1st Floor TV, but only get on the 2nd Floor TV (WSOC-TV, WTVI-HD, WTVI-MV, WTVI-Ct) all have "Signal Strengths" on the 2nd Floor TV of 89% or higher. In fact, there are stations that I got on both TVs, for which the signal strength on the 2nd Floor TV is lower than 89%. Doesn't really make any sense to me.

Also, can you confirm that "front" and "back" of antenna is as I think in the picture below?

http://forum.tvfool.com/attachment.p...1&d=1453771974

No problem; it takes time to do it right. And it's going to take time for us to digest your results and think of an intelligent helpful comment.:)
Every manufacturer does it a little differently. The percent scale is only relative, not absolute, but it is very useful for comparisons. The signal strength is similar to the NM dB or Signal pwr dBm scales on your tvfool report. The Signal Quality is probably SNR (Signal to Noise Ratio).
Your labels are correct.
It doesn't make sense yet to me either.

There are three possibilities. The loss in the coax line to the first floor is more than estimated. As a test, run a temporary coax line to the 1st floor to bypass the in-wall coax run.

The 1st floor tuner is more sensitive to overload than the tuner in the 2nd floor TV. Try inserting various values of attenuation between the antenna and the input of the 3412. A 2-way splitter has a loss of 3.5 dB, a 4-way 7 dB.
https://www.antennasdirect.com/store...ttenuator.html
http://www.3starinc.com/drop_in-line_attenuator.html
http://mjsales.net/collections/atten...ant=1083705673
•Attenuation values 1, 3, 6, 8, 10, 12, 16, 20dB (FAM)
click on 1 dB for other values; the up and down arrows are faint

The tuner in the 1st floor TV is less sensitive than the tuner in the 2nd floor TV. To test this theory you would need to move the 2nd floor TV down to the 1st floor.

Is it safe for me to assume that you do a tuner rescan of the 1st floor TV after a change?

For "Signal Quality", I assume 100% is the ideal? Almost every station was at that value, so it looks like I don't have any signal quality issues.

My observation below would seem to cast some doubt on the first possibility, wouldn't it?


I will have to look into the other 2 possibilities. Finding a cable long enough, or a short enough path for my existing coax could be an issue. I could possibly run from the antenna straight to the wall the 1st Floor TV is mounted to, but I'm guessing I'd run into some 2X4s going down 2 stories. If only I could get signal strength readings from the 1st Floor TV.

Yes.