Reception problems with certain channels in Ames, IA

TheLoo · 31-Dec-2011, 2:29 AM

Hey everybody,

We finally decided to get rid of our dish and go to OTA TV. I live in Ames, IA and ran through the TVFool Signal Analysis ( http://www.tvfool.com/?option=com_wr...403359b8f49a3e ).

Almost all of the transmitters are located in the same area (outside a small town named Alleman which is only 15 miles from my house). According to the signal analysis results I should be able to get decent reception even with an indoor antenna.

I have installed an outdoor RCA antenna that I got at Lowe's with a 110" boom and a range of 65 miles (according to the box). I mounted it on the mast that was already set up on the roof of my house for the dish. I have a single story house, and in the interest of full disclosure, I should point out that with the location of the dish mast, the new antenna doesn't quite clear the roof line. I figured if an indoor antenna was supposed to work, I'd probably be OK, and for the most part everything is really great. According to my TV I get about 97 signal strength on NBC, CBS, and IPTV.

However, on ABC and Fox I get significantly lower signal strength, sometimes dipping low enough to cause some pixelation even on clear days. I'm confused as to why those channels aren't as strong as the others since the emitters are supposed to be in almost exactly the same place and since the antenna should be overkill for the job. The only thing I've come up with so far is that Fox is UHF, and for some reason in the chart WOI (ABC) is listed twice, once as VHF and once as UHF. I'm wondering if there is some reason that my UHF reception would be lacking.

I'm pretty new to the whole antenna thing, so I don't really know what the next step is. I could add a preamplifier, but right now I only have the signal split to run to 2 TVs with a total cable length of maybe 150' max, which doesn't seem to warrant much amplification. Are some antennas bad at UHF reception? I had read that it was more common for people to have better UHF reception and poor VHF reception but I seem to have the opposite problem, assuming that is is related to UHF vs VHF at all.

By the way, removing the splitter and running straight from the antenna into the TV doesn't seem to affect the signal very much.

Any help anybody can give me would be greatly appreciated.

Thanks,
Forrest

GroundUrMast · 31-Dec-2011, 4:21 AM

Do you have the model number of your RCA antenna?

Is it aimed toward the south? (The longest elements perpendicular to the boom are at the back, the shortest elements are at the front of the antenna.) I ask because many folks mistake the front and rear of their antenna. As I drive around, I'm amazed by the number of antennas I see aimed 180° or 90° off.

Is there any chance that water has entered the matching transformer or coax?

Most satellite J-pole mounts are located on the south side of the building so the dish will have a clear view of the southern sky. I not able to picture your situation.

Electron · 31-Dec-2011, 4:33 AM

Here is how to aim antennas , http://www.kyes.com/antenna/pointing/pointing.html , Aim the antenna at 168 degree magnetic compass. Also the antenna needs to be level with the ground , Not pointed up at the sky , Not pointed down at the ground , Not tilted to the left or right. What is the model number of the antenna?? In any event the antenna will need to be higher then the roof.

ADTech · 31-Dec-2011, 11:40 AM

Most likely, you have the RCA ANT3036 which should be appropriate to your area.

WOI is listed in the chart twice because they operate two transmitters in the Des Moines market. They operate their so-called "full power" signal on VHF 5. Because of problems they discovered post-transition with indoors reception and low-VHF, WOI applied for and received permission to operate a low-power fill-in translator in downtown Des Moines so their signal could be better received in the urban portion of the city with indoor antennas.

Many sets and converter boxes have, as part of the signal meter or diagnostic screen, information about the RF frequency or channel that is being received. Check yours for WOI's signal. RF 5 will be in the 80 MHz range while channel 50 will be up around 690 MHz. Each of these signals would be received by different sections of your all-channel antenna. RF 5 would be received by longer elements in the back of the antenna while RF 50 will be received by the narrower Yagi front end of the antenna.

Reception of channel 5 would be most likely affected by interference from electrical devices or from having the antenna too close to metal objects such as guttering, soffit, fascia, drip edge, metal plumbing pipes, electrical wiring, and other such objects that are either too close to the antenna or are causing an adverse reflection of the signal resulting in multi-path distortion of the signal.

Problems with reception of the UHF signals are usually due due to either trees or other objects in or near the line of sight or from the metal-related items above.

Your best bet would be two-fold:

1) Look at your line of sight towards the broadcast towers and observe whether there are obstructions that might be avoided by mounting the antenna elsewhere.

2) Move the antenna to that point ensuring you get some elevation (5' min) above the roof line. Don't drill any holes until you've tested reception in a given location.

Keep in mind that the most convenient or available location for an antenna sometimes doesn't necessarily correspond to the required signal strength and quality at any given spot. There's a very good reason that the old-time antenna professionals developed the skill called "walking the roof" with a test antenna and a signal meter.

TheLoo · 5-Jan-2012, 8:25 PM

Thanks to everybody for the responses, and specifically to ADTech for enlightening me on the reasons for the multiple WOI stations. The antenna is definitely pointed in the right direction, and in the proper orientation. It is very close to the edge of the roof which could mean that the guttering and/or fascia could be affecting it. There are trees close to the antenna but behind the antenna (i.e. not in the line of sight). Could those be affecting reception at all?

I am going to try to increase the height and see if that works, and if not I may have to try finding another place on the roof for the antenna. If I had to pick a winter to be standing around on my roof a bunch of times, I guess I could have done worse than this year.

Thanks again,
Forrest

Electron · 7-Jan-2012, 4:28 AM

If the antenna matching transformer that connects the antenna to the coax is not new and the outside coax is not new , then replace with new. All out side connections are suspect of being bad.

TheLoo · 21-Jan-2012, 1:53 AM

OK, after giving up for awhile, I went back to the issue while setting up a Windows Media Center PC as a DVR (which is pretty great, BTW). It seems to me like I have found out my problem, but I'm wondering if anyone can confirm my suspicions, and suggest a solution.

After scanning for all the channels in Windows Media Center I realized that I had 2 different signals for WOIDT (the station with both a lovhf and uhf signal). The low VHF signal is very good, but the UHF signal is pretty bad (which makes sense given where the antenna is pointing and where the UHF signal is coming from). If I disable the UHF channel, then I can watch ABC with good signal on my PC.

However, on my TV it seems like it finds enough signal to map the UHF channel (50.1) to 5.1, and my 5.1 from the VHF (I'm guessing) gets overwritten. Does this sound possible? Is there any way to keep that from happening?

Thanks in advance for any help!

Forrest

ghz24 · 22-Jan-2012, 2:28 AM

Most all band antennas have higher gain and narrower beam in the UHF and lower gain and wider beam on VHF.
So miss aiming the antenna a little (while you're doing your channel scan) may hurt the UHF signal more than the VHF signal. That may make the TV pick the VHF and not see the UHF.
After you scan you should be able to re-aim for best all around reception.

Another ides is most TVs scan up and 50 is near the top so when the scan is almost complete pull the antenna connection so when presumably it is looking for a station at channel 50 it wont see anything.

Try the second one first (you can stay in the warm if that works and saves two trips too the roof)
Have to wait for 48 though.