Chicago inconsistent reception
 

http://www.tvfool.com/?option=com_wr...e6a42030dccec3

I have a Winegard HD7084P antenna, mounted since 2012 in the attic of a single-story house. I'm getting excellent reception on all channels, with the following exceptions: WTTW (ch 11) is all but unwatchable (only started earlier this year-- before then was fine), and WFLD/Fox (ch 32) sometimes is fine, sometimes has annoying momentary freeze-ups (especially distracting during football games).

I have the signal split to 2 TV's.

I'd really like to fix these reception problems. But I'm not sure what I should be looking to do. Amplifier? Move antenna to roof (might be a cosmetic issue)? New/different antenna?

You have one of the strongest radar plots I've ever seen on here. You could try adjusting your aim a bit, or perhaps using a powered splitter?

Do not use any amplifier. Signals are already calculated (and assumed) to be moderately strong. Inappropriate amplification often opens up the system to new problems.

Changes in reception over time are always due to changes in either the system or it's local environment over time.

Corrosion or water ingress can cause degraded reception. Not likely for an attic install, though.

Most common problem, though, is the growth of trees in or near the signal path over time. Due to the "cliff effect" inherent to digital TV, reception will appear normal right up to the point where it isn't normal anymore. Usually, degraded reception starts with only one or two channels whose frequencies just happen to be the ones most drastically affected first. You'll need to look at your signal path with a critical eye for those kinds of details. Moving the antenna usually changes the results.

Other changes in the immediately local environment (construction, local noise sources, etc) can alter the signal path or environment and also cause degraded reception.

Welcome back, dongna

I was wondering why you ended up with a big all-channel antenna in your attic. Your previous thread tells the story of why:

Directionality of antennas
http://forum.tvfool.com/showthread.php?t=7131

The answer by ADTech seems to explain why your reception has changed.

The strength of the signals in the attic is most likely less than indicated on your report, but we don't know how much less because of differences in construction.

Before we could give any further advice, we would need to have some idea of the actual strength of the signals in your attic, and see some photos of your property and maybe even a satellite view of your house.

To protect your identity, you would need to give us your location or coordinates in a PM, but you might be willing to show us some photos in this thread.

I have attached a google maps photo of my house. The yellow arrow attempts to depict the approximate direction of the signal from the source to my antenna, which is located in the attic at the head of the arrow.

As for growth of trees, I live in a mature neighborhood and I can't imagine there has been any significant tree growth that could be suddenly causing these issues. In general the tree density is what I would consider moderate-- there are trees around but I'm not in the middle of a forest or anything. Likewise, my 'burb is a fairly sleepy one with no buildings over two stories for miles around. Terrain is generally very flat all the way to the source of the signal.

House construction is 2 x 4 exterior walls, cedar siding. Built in the 60's. Roof is typical asphalt shingles (one layer).

If there are any other photos that might help diagnose the problem, just let me know and I will happily accommodate.

Thank you for the photo; it helps.

http://forum.tvfool.com/attachment.p...1&d=1505587889

If you use the TVFool Interactive map, you can add the green signal lines.
http://www.tvfool.com/index.php?opti...pper&Itemid=90

http://forum.tvfool.com/attachment.p...1&d=1505588166

The satellite image was taken when the leaves were off the trees.

I have looked at some ground photos of your location by Google and Bing showing trees that might interfere with TV reception. Please see the PM I sent to you.

http://www.hdtvprimer.com/antennas/siting.html
scroll down to Trees and UHF

Trees keep growing every year. I suggest you wait to see what happens when the leaves are off the trees.
A photo looking from the rear of the house toward 125 true/129 degrees magnetic might be helpful.

If the antenna were moved a little down south in the attic, it might aim between the two largest trees in the SE. That might be difficult with your big all-channel antenna.

A UHF-only antenna would be easier to move around in the attic, but you would still need a VHF-High antenna for WBBM CBS on real channel 12.

Another possibility would be an antenna outside that aims below the lower branches, or an outside antenna aimed between the trees.

Wow, I can't thank you enough for the attention you've given to my little problem. (Your PM's have the correct house). I've attached a picture from the roof standing right over the antenna position pointing towards the signal source.

I went up in the attic this morning and double checked the aim on the antenna-- it might have been a few degrees off optimal, so I tweaked that a little. Didn't seem to make any significant difference-- WTTW was still heavily pixelated.

I'm still bothered by the fact that WTTW used to come in just fine. In fact, just last night I watched a Frontline that I had DVR'd about a year ago, and I watched 2 hours with not one glitch. So while I certainly don't want to discount that this is a tree issue, given the maturity of the trees in question I'm suspicious that there's not something else at issue here.

You're right, it would be difficult to relocate the antenna in the attic because of it's size. Especially moving it south would be impossible because there's a chimney that runs through the attic in that area. The only option would be to move it south and west, but I rejected that location originally because it would then be behind the chimney (at least partially).

What about trying to raise the antenna up or down 5-6 inches? I read somewhere else that this might help, and that would seem to be supported by the link you provided earlier that describes the "layering problem".

Any opinion on whether moving the antenna up to the roof would help? I would still be well below the trees you pointed out. I guess I don't know how much signal there is to be gained by it not having to pass through the roof of the house and being just a little bit higher.

I would also be open to a different antenna if it would allow more flexible positioning, whether in the attic or on the roof. Especially a smaller one might not be objectionable to my wife if mounted on the roof. But I would have to start that whole research cycle again.

Thank you for the confirmation of your location. I knew your approximate location from your report, but it took me an hour staring at the satellite image to find your roof. Your image gave me a clue.

Thanks for the photo from your roof. It shows trees thick enough to interfere with TV signals, especially when wet. I wonder how the reception will be when the leaves fall.
WTTW is on real channel 47, virtual channel 11.1, so it requires a UHF antenna. If you must use the virtual channel number, please use the decimal form to avoid confusion.

It is the real channel number that determines what antenna is needed.

VHF-Low, real channels 2-6
VHF-High, real channels 7-13
UHF, real channels 14-51

The virtual channel number (like 11.1) is a holdover from the analog TV days to maintain the identity of the station, and is what the TV displays.

The reason why WTTW is affected, but not other UHF channels, is because the signal is scattered as it moves through the trees. The scattering pattern is not the same for different frequencies.
It might help; no guarantee. The trees and the roof have already done damage to the signal.
That would be another try it and see experiment. It would avoid the roof loss, but not the tree interference. There is no magic antenna that can "see" through trees.
If you are willing to experiment, I suggest the Antennas Direct DB4e. WTTW will be moving to channel 25 because of UHF repack. The DB4e and the DB8e were rescaled to give more gain at the lower end of UHF when it was reduced to 14 to 51.
http://www.rabbitears.info/market.ph...&callsign=wttw

The DB4e is primarily a UHF antenna. If it doesn't pick up WBBM on real VHF-High channel 12, combine the DB4e with your present antenna using a UHF-VHF combiner (UVSJ).
https://www.antennasdirect.com/store...Combiners.html