Dallas, TX - Fox/KDFW Reception Issues

[misterpants]

I'm having a problem getting acceptable reception for a single network (Fox/KDFW) in North Dallas and was hoping someone here might be able to help out. I'm trying to err on the side of giving too much information so please forgive me in advance if any of this is overkill.

Based on my Signal Analysis report (link here), I purchased an indoor/outdoor powered antenna from Monoprice.com (product link). I have the antenna mounted in my attic using a similar setup in the pictures here, and I'm using 100 ft. of 75Ohm Quad Shield CL2 Coaxial Cable to connect the antenna. I do not have radient barrier in my attic and there are some trees in my front lawn in the antenna's path along with some high power lines about 2 blocks away.

I only really care about the major networks and this antenna picks up ABC (WFAA 8-1), NBC (KXAS 5-1), and CBS (KTVT 11-1) flawlessly; however, the reception on Fox (KDFW 4-1) is either too blocky to watch or doesn't pick up at all.

These stations are all less than 31 miles from my house and are all within 2 degrees of each other in direction. I would think it's my equipment, but I'm receiving stations perfectly that are closer and further away and have higher and lower signal strength in my signal analysis report than the problem station.

Any ideas on what I could try to address this?

Thank you for reading!

[John Candle]

As is always , the type and kind of amplified antenna shown in the picture is a very undesirable antenna to use for Tv reception. The tv transmissions at your location are very strong and the amplifier in the antenna is likley overloading and the small size of the antenna violates the laws of physics. The antenna in the picture is pointed in to all of the roof supports - block after block after block of wood , what kind of deal is that ?? A real bad deal. I suggest a Winegard HD7694P antenna , point the HD7694P antenna at about 194 degree magnetic compass. Here is how to point tv antennas , http://www.kyes.com/antenna/pointing/pointing.html . Also read and understand this about , REAL Digital Tv Channels , Virtual Digital Tv Channels , Analog Tv Channels , http://forum.tvfool.com/showthread.php?t=695

[John Candle]

The Tv transmissions at your location are very strong , a amplifier is not needed.

[John Candle]

Here are places to buy Tv antennas and etc. . http://www.solidsignal.com , http://www.3starinc.com , http://www.starkelectronic.com

[John Candle]

How many Tv's are connected??

[ADTech]

Amazing. Four posts to NOT answer the question.

Mr Pants,

Your amplifier is not overloading. The antenna you have is a fair UHF antenna and it's design and capabilities are generally appropriate for the "problem channel" that you have. That said, it is lacking a feature that is likely contributing to your one-channel problem, that is, something to improve its directionality and focus.

Your problem is best described as a "single-frequency multi-path" fault. There is a set of factors that is causing that one channel's signal to be oddly reflected or distorted before it gets to the antenna. That might be those trees, the power lines, the house across the street, a nearby tower or other structure, or an echo produced within your attic.

As your antenna both lacks a reflector and exhibits a very wide reception beamwidth, it is not capable of rejecting interfering/reflecting signals that are the likely cause of your single channel problem. Short of buying a different antenna with different performance characteristics, you really have one option available to you: Move the antenna somewhere else and try again.

I run into this issue with callers just about every week and the solution I've suggested works very well. In your case, try several different spots in the attic. If improvement isn't made, try the antenna outdoors in several locations.

Good luck!

[misterpants]

John Candle:
Thank you for taking the time to respond! If I decide to purchase a different antenna, I’ll definitely take a look at the Winegard model you suggested. Also, the picture of the install I linked isn’t my actual installation, Mine is pointed basically directly at the roof without any support beams in the way. I just wanted to show what type of install I was using with PVC pipe used to gain additional height and those pictures used my same antenna and install method. Ideally, I would like to have the antenna support two TVs, but right now, I’m only connecting to one. The second TV is a “nice to have” and I wasn’t planning on trying to deal with that TV until I get a reliable picture on one TV.

As for the potential for overload, I tried connecting the antenna this morning without the amplifier and didn’t pick up a single station when I rescanned. While I realize that doesn’t prove I’m not overloading the amplifier, wouldn’t that rescan combined with the fact that I’m receiving a perfect signal on other channels with the amp plugged in minimize that possibility?


ADTech:
Thank you for the detailed response! I’ll definitely try moving the antenna around this afternoon and report back with results. While I’d prefer to stick with this antenna to avoid the hassle of shipping off a return, I’m still within my return window from Monoprice so I could potentially go with a different model if necessary.

Based on your diagnosis, would something like the DB4 be more appropriate since it has a reflector? If not, is there a different model you would recommend that might work better for an attic installation?

[Tower Guy]

Originally Posted by ADTech

Your amplifier is not overloading. The antenna you have is a fair UHF antenna and it's design and capabilities are generally appropriate for the "problem channel" that you have.

While this is generally true, I'm not so sure that the antenna is not overloaded.

I count 20 TV stations between -32 dbm and -44 dbm average power with a peak to average ratio of 6 db. When these stations combine before the preamp their voltages add such that the peak voltage has an equivalent power in the vicinity of -4 dbm. (assuming zero loss through the walls and zero antenna gain) The amplifier in the Monoprice is rated at 20 db gain. That implies that the amplifier has to have an output 1 db compression point of at least +16 dbm to avoid overloading. There's no spec posted on the Monoprice amplifier, but I'd be very surprised if it is capable of +16 dbm undistorted output.

[misterpants]

Originally Posted by Tower Guy

While this is generally true, I'm not so sure that the antenna is not overloaded.

Thanks for taking the time to respond. I’ve tried to educate myself on various antenna-related terminology but I’ll admit up front that I’m still struggling a bit with understanding the science behind it all. If I understood though, you’re saying that the monoprice antenna might be too weak to pick up the stations without the amp, but the station signals might be too strong for it to pick up with the amp without overloading; correct?

If amp overload is the culprit, do you have any thoughts on why this would be a problem on only one station (Fox) while other similar stations (ABC, NBC, and CBS) with almost identical signal strength, distance, and direction are all coming through flawlessly?

[Tower Guy]

Originally Posted by misterpants

Do you have any thoughts on why this would be a problem on only one station (Fox) while other similar stations (ABC, NBC, and CBS) with almost identical signal strength, distance, and direction are all coming through flawlessly?

That's the right question.

One possibility is that channels 30 and 32 form a 3rd order intermodulation product that extends from channels 34 through channel 35. In addition, channels 29 and 32 create an IM product that falls on channels 35 & 36. KDFW is on channel 35. The complete technical explanation is here: http://www.tvtechnology.com/article/73532

If that's correct, the solution would be a non-amplified antenna.

[ADTech]

TG,

My opinion is based on the report of only a single channel suffering a problem. If IMD was occurring inside the amplifier, it would be unlikely for it to affect only one channel except by extraordinary coincidence. That said, I've learned the hard way to not rule anything out...


Mr Pants,

No, the DB4 would not be a reliable choice as it would likely cost you WFAA unless you added a dipole for high-VHF. Out of the box, the 7-69 antenna (or a comparable model) suggested by JC would be be logical. The Yagi UHF section of that style antenna is quite good at reducing reflections from the side and rear and would be expected to resolve multi-path issues.

[Tower Guy]

Originally Posted by ADTech

TG,

If IMD was occurring inside the amplifier, it would be unlikely for it to affect only one channel except by extraordinary coincidence. That said, I've learned the hard way to not rule anything out...

Also read annex G on page 83 of the ATSC standard.

http://www.atsc.org/cms/standards/a_74-2010.pdf

[ADTech]

Good point. Thanks for the heads up.

[GroundUrMast]

So the theory aside,

1. Move the existing antenna in the attic, looking for a 'sweet spot'.

2. Try the existing antenna outside. (If the amplifier is on the verge of overloading in the attic, the situation will be worse outside where the signals will be stronger. FWIW, unplugging the power supply does not remove the amplifier components that are located inside the antenna housing. Few amplified antennas provide means to bypass the amplifier.)

3. Replace the existing antenna with a moderately directional, medium gain antenna designed for reception of real channels 7 through 51. (The suggested HD7694P for example.)

[misterpants]

Firstly, thank you all very much again for reading and for the several detailed replies and suggestions. I tried repositioning my antenna and wanted to report back with the results.

I previously had the antenna about 4 feet high in the attic (12’ from ground) so that I could keep it close to the entry hatch for easy adjustments. I tried raising it up to about 7 feet high in the attic (15’ from ground) and moved it more towards the center of the attic and my while my signal bars actually decreased for other networks (CBS and ABC) without visibly impacting the picture, the Fox signal improved and I’m now only getting the occasional glitch/blip. (I should mention, I’m measuring signal through my Samsung TV which only gives signal bars rather than a percentage.)

The skeptic in me is concerned however as today happens to be a particularly clear sunny day in Dallas with hardly a cloud in the sky. Based on these results and my previous issues with this antenna, would you all recommend I go ahead and pick up the Winegard HD7694P antenna referenced earlier to better safeguard against potential future bad reception and/or poor weather conditions? If so, would you expect I would need to pick up an amp as well or should the antenna alone be sufficient (assuming similar conditions in an attic installation)?

I have about a week and a half left in my return window to monoprice and I’d hate to be stuck with an antenna I don’t need. I may just go ahead and order the Winegard to tinker with and compare over the weekend, but I’d appreciate any other ideas/expectations any of you may have as well.

Thanks again to you all for your help!

[GroundUrMast]

I would not have recommended an amplified antenna to begin with. The HD7694P will not need an amplifier. If installed outdoors, in the clear, it should provide sufficient signal power to drive an 8-way split.

An attic is an unpredictable and variable environment. If you are able to get acceptable reception with your antenna protected in the attic, great, you will get nearly unlimited life from your antenna. If reception fails during wet weather, you'll need to decide if that is preferable over moving the installation outdoors.

[John Candle]

Like I said , AD Tech . The antenna violates the laws of physics and it also violates the laws of wave length reception. The plastic case is 4 3/16 inch wide and 7 9/16 high. So what is the actual metal receiving element size?? These magic Tv antennas are trouble any which way Ya look at it , connect it , adjust it. The market is flooded all manner of magic Tv antennas and people lap it up. I have stated many times here at tvfool that the market is flooded with scam antennas.

[ADTech]

"Any sufficiently advanced technology is indistinguishable from magic." Arthur C Clarke, Author.

If your knowledge of antennas is limited 1/4 wave dipoles and their derivatives, then any compact antenna will seem to be "magic". Otherwise, how do you explain the antenna in an LTE handset/USB modem (700-800 MHz) or the similar cellular band antennas that operate between 800 and 900 MHz? (Bonus points awarded for the correct answer.)

The OP's antenna IS suitably sized for UHF reception and, despite its compact size, IS working for his single high-VHF channel and it isn't magic.

[John Candle]

AD Tech . Here at tvfool I help the question askers receive the Tv channels with the least amount of problems. My self and the other helpers here at tvfool do not agree with you.

[ADTech]

Originally Posted by John Candle

AD Tech . ... My self and the other helpers here at tvfool do not agree with you.

Really....?