Help selecting antenna

Chasseur · 21-Oct-2010, 2:25 AM

Here is my location:
http://www.tvfool.com/?option=com_wr...a362035933ca85

I currently have an antenna installed in the attic. However, I get some pixellisation often during a tv show. Maybe I don't have the right type of antenna.

I only care about digital channels 19, 20, 27 and 42.

Here is my current 4bay antenna:
http://www.vi-tesse.com/shop/view.as...&idCategory=53

Thanks a lot

GroundUrMast · 21-Oct-2010, 3:00 AM

Your antenna looks like a good choice. It has some gain and is not as critical about aiming as larger antennas often are.

However, you should still try adjusting the aim in small steps to be sure you have the best signal available. In this case I expect the antenna to do best when it is facing just a bit south of due east.

Also, are there wires or metal ducts near the antenna, if so, try moving the antenna away from those metal objects.

Be sure to examine connections for looseness and check that the coax is not bent sharply or otherwise damaged.

Tigerbangs · 21-Oct-2010, 1:12 PM

Most people in the Montreal area are used to seeing the Burlington= Pittsburgh TV stations, and I suspect that you are having some difficulty with your US stations. WVNY and WFFF, ABC and FOX respectively, are the hardest stations to get in the Montreal area, and WVNY is on VHF channel 13, and is usually not well-received on a UHF only antenna. You may want to reconsider your attic installation, even thought the weather in your area can be harsh, and add a VHF yagi like a Winegard YA-1713 aimed at Mt. Mansfield. The Mt. Royal stations in Montreal should be no problem, but, remember that they will go all-digital by August 31, 2011, and you may then need a rotator to see the Mt. Royal stations AND the Mt. Mansfield stations.

Chasseur · 21-Oct-2010, 3:21 PM

I'm able to receive a few US stations, but the reception is borderline. However, my priority is on receiving Montreal stations without glitches.

My RG6 cable goes from the antenna in the attic to the basement. The cable is about 40 feet long.

Signal strength: 50%
Signal quality: 75%
Symbol Quality: 100%, but sometimes drops to around 60% for 1 sec.

I guess I'm seeing corruption when having small symbol quality drops...

Chasseur · 21-Oct-2010, 9:02 PM

I'm also wondering:

Wouldn't a directional antenna work better for my situation? Maybe it would pick less interferences than my current antenna?

GroundUrMast · 21-Oct-2010, 9:14 PM

If you are having interference problems, a more directional antenna might help.

I would experiment with moving the existing antenna (outside if possible) before I spent the money on another antenna. Moving an antenna up/down or sideways can sometimes have surprising results.

You said, "I only care about digital channels 19, 20, 27 and 42." Per the radar plot, those stations are close together so if you choose to try a more directional antenna, you should not have a problem aiming at the group.

Tigerbangs · 21-Oct-2010, 10:31 PM

[/QUOTE]You said, "I only care about digital channels 19, 20, 27 and 42." Per the radar plot, those stations are close together so if you choose to try a more directional antenna, you should not have a problem aiming at the group.[/QUOTE]

And, if you add a VHF-high-band plus UHF antenna and a rotator on the roof, you'll not only see the the Mt. Royal stations, but also the Mt. Mansfield, VT stations, as well. I recommend a Winegard HD-7696P mounted on top of a good rotator like a Channel Master 9521a or an AntennaCraft TDP-2. Rooftop mounting will help you with ALL of your stations, as roofing material, insulation, and such severely cuts down on the signal available to your antenna, and will can cause the multipath distortion that you are currently see as pixellization and picture dropouts.

Chasseur · 22-Oct-2010, 2:07 AM

What I don't understand is why I only get 50% of signal strength. I guess it should be stronger for the specified channels...

Tigerbangs · 22-Oct-2010, 2:55 AM

You have mistaken the signal quality meter on your tuner for a signal STRENGTH meter: the two are quite different.

Signal strength is a measurement of raw signal, and a digital tuner can see quite a strong signal and still show low signal quality if the signal-to-noise ratio of the data stream is compromised by interference. The symptoms that you have described, where signals come and go is a classic sign of multipath interference, which occurs when direct signal and reflected signal arrive at the antenna at slightly different times.

In the analog days, multipath was easy to spot: it showed up as ghosting on your TV screen: the phenomenon of seeing multiple images on a TV screen. Multipath is usually an urban issue, where TV signals are very strong: strong enough to bounce off objects like buildings, trees and hills, however, it can occur where indoor or-attic-mounted antennas are used in suburban and even rural settings, where the signals can be refracted by airplanes flying overhead.

Attic installations are usually trouble in areas of strong signals because the TV signal can often be refracted by some of the building materials used in the house. Modern digital TV tuners have increased resistance to multipath interference, but they are not completely immune to it.

The best solution to the issue of digital signal dropout, and low signal quality is to use a highly directional antenna that is mounted as high as is possible, aimed precisely at the transmitting tower, and free of close-by obstructions such as trees, hills and taller buildings. Please remember that preamplifiers can restore signal loss incurred by splitting a TV signal to multiple TV sets, or can help overcome line losses incurred by very long cable lengths, but are often mistakenly prescribed in strong signal areas for issues that are more properly addressed by using a better, more directional antenna, and precisely aiming the antenna. Preamplifiers can be a liability in areas where signals are very strong, however, because they often overload and cause a worsening of the signal-to-noise ratio.

A rotator is a very useful device when it is necessary to point an antenna at different transmitters. In your situation, a rotator and the right antenna system can easily double the number of TV stations available to you, and can minimize the issues of low signal quality and multipath.

Chasseur · 22-Oct-2010, 3:21 PM

Thanks for your support, I really appreciate.

From what I understand, my signal level should not be a problem, but it would if I try to split the signal. In that case, I would need an amplifier?

I've made a few more tests. I tried moving the antenna again, but the signal remains the same.

I also discovered that I have some Interference issues. When playing with the house light switches, I get pixelisation. Same thing when the motor of my ice machine starts.

Maybe all my problems are only related to interferences.

GroundUrMast · 22-Oct-2010, 7:32 PM

Tigerbangs has summarized two or three complex topics concisely and as accurately as I could hope to. His general advice of elevating the antenna would provided the benefit of getting further from interference sources such as certain types of lighting fixtures and motors.

Regarding an amplifier, I would add it only if it proves necessary. The benefit of an amplifier comes at the cost it's imperfections. All amplifiers will add some noise to the signal and will distort the desired signals to some degree. They have their place.

John Candle · 22-Oct-2010, 8:09 PM

Move the antenna to the roof and away from the wiring in the attic

Chasseur · 22-Oct-2010, 10:09 PM

Thank you all.

I guess I will get a directional antenna for the roof. If I get satisfied with this setup, maybe i'll upgrade with a rotator later to grab other channels.

One more question regarding the coax wiring: is it possible that some interferences are being grabbed by the RG6 cable and not the antenna?

GroundUrMast · 22-Oct-2010, 11:14 PM

Quote:

Originally Posted by Chasseur

Thank you all.

I guess I will get a directional antenna for the roof. If I get satisfied with this setup, maybe i'll upgrade with a rotator later to grab other channels.

One more question regarding the coax wiring: is it possible that some interferences are being grabbed by the RG6 cable and not the antenna?

Coax can fail, but the most common problem I can think of would be a bad connection between the coax shield and connector body. That will allow signal to 'leak' into and out of the coax.

Tigerbangs · 23-Oct-2010, 2:06 AM

If you are using multiple TV sets, it may behoove you to use a distribution amplifier/splitter to recover the signal losses associated with cable and splitting losses. You are close enough to the Mt. Royal stations that I believe that you may have issues with signal overload if you use a mast mounted preamplifier, but an indoor distribution amplifier, possibly with an Fm trap installed, should solve low signal issues.