# OTA for 921



## jackson3 (Jan 8, 2005)

Question for the Gurus:

My first OTA antenna for the 921 was a Radio Shack model that didn't work well at all. My second choice was a Channel Master 4221. Before I connected it to the mast on the roof, I gave it a try in my living room, which is situated behind my roof covered front porch. To my amazement, all the digital channels locked on. But, after moving the Channel Master onto the roof, I wasn't able to lock on to ABC. All of the digital channels in the Pittsburgh area are from 6-14 miles away from my home. Most of the channels are in the 15 to 20 degree range, except for ABC, which is 128 degrees away. My question, why did the antenna pick up the signal from ABC in the living room but couldn't pick it up on the roof with a clear line of sight of ABC's tower? Was the signal, maybe, being reflected enabling me to pick up ABC in the living room? Any suggestions on an antenna that can pick up signals from 15 to 128 degrees away? Any help would be appreciated. Just wanted to let you all know that my 921 has worked pretty well since, February, without missing any scheduled programs. I had to reboot many times to unfreeze a frozen unit but other than that it has performed nicely. The picture quality on HD OTA is outstanding on my 64" Pioneer Elite rear projection TV. Thanks everyone, Ed


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## boylehome (Jul 16, 2004)

jackson3 said:


> Question for the Gurus:
> 
> My question, why did the antenna pick up the signal from ABC in the living room but couldn't pick it up on the roof with a clear line of sight of ABC's tower? Was the signal, maybe, being reflected enabling me to pick up ABC in the living room? Any suggestions on an antenna that can pick up signals from 15 to 128 degrees away? Thanks everyone, Ed


Most likely your antenna is in a dead spot for ABC or needs to be aimed at ABC. You got a very good antenna but it is very directional. If you can, rotate it to the direction of the ABC station (if it isn't already), if that doesn't help, try changing its height. If aiming it at ABC helps, you may lose your other channels. If this happens then try to lower it if you can then check to see how it works. If that doesn't help, changing the physical location may. Otherwise, you may need to put a rotator on it so to aim it or you may need to make an antenna array (if all your channels are relatively close to you) so to receive all of them. When you tried the antenna in you living room signals were bouncing off of different surfaces thus allowing the reception of all your channels from the living room. The new antenna does a better job at rejecting side and back signal which other wise would be a cause of multipath for digital OTA.


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## bbomar (Oct 18, 2004)

jackson3 said:


> Question for the Gurus:
> 
> My second choice was a Channel Master 4221. All of the digital channels in the Pittsburgh area are from 6-14 miles away from my home. Most of the channels are in the 15 to 20 degree range, except for ABC, which is 128 degrees away. My question, why did the antenna pick up the signal from ABC in the living room but couldn't pick it up on the roof with a clear line of sight of ABC's tower? Was the signal, maybe, being reflected enabling me to pick up ABC in the living room?


You may have too much antenna considering how close you are to the
transmitters. Multipath can prevent locking on to a signal and you may
have strong reflection signals with the antenna outside, plus the ABC 
direct signal may be in a null of the antenna since it is very directional.

I have not tried the Zenith silver sensor but I have read on a local HD
forum that some folks near transmitters in the Huntsville, AL DMA have
had good luck with it.

http://www.solidsignal.com/prod_display.asp?main_cat=03&CAT=&PROD=ZHDTV1


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## Michael P (Oct 27, 2004)

The Pittsburgh area is very hilly, so the chance for dead spots are great. Besides "dead spots", the chance for multipath is even greater. Multipath, while an annoyance in analog, is the kiss-o-death to digital OTA reception. You must aim the antenna dead-on to 128 degrees to get WTAE. You can thank the fact that for years WTAE was the only ABC affilliate for 3 different markets (besides Pittsburgh, add Johnstown/Altoona & Wheeling/Steubenville), which is why they are not co-located with the rest of the pack of P'burgh transmitters. While Altoona finally got their own ABC about 13 years ago, WTAE is still the source for ABC to Wheeling/Steubie. IIRC one of the Wheelilng/Steubie stations (the NBC) moved their transmmitter into PA (physically outside the DMA they serve). 

Why did you have better luck indoors? You stumbled upon a "sweet spot" that you may want to return to.


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## Michael P (Oct 27, 2004)

> I have not tried the Zenith silver sensor but I have read on a local HD
> forum that some folks near transmitters in the Huntsville, AL DMA have
> had good luck with it.


I own a Silver Sensor, it's great! I use an A/B switch between the Silver Sensor and a rooftop omnidirectional "saucer" antenna which is 20' above my roof. The indoor "SS" gets staions farther away than the outdoor omni . I watched Youngstown stations (55 miles away) last night for the first time (aided by "skip"). I use the SS to get the Akron/Canton "rim-shots" that the Omni misses (skip not a factor here - these stations are in my DMA but there are terrain obstructions that have to be compensated for by moving the SS to a "sweet spot" - a different spot for each station). I use the Omni to get the closest (and most watched stations) and only flip to the SS when I want to watch or record one of the rim-shots.


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## jackson3 (Jan 8, 2005)

Thanks for all the good information. There sure are a lot of knowledgeable people on this thread. I even got an education on why WTAE (ABC) is located away from the other channels in Pittsburgh. I did try and move my Channel Master up and down and back and forth on the antenna mast but that didn't help with ABC. I'll give the Zenith antenna a try, with an A/B switch wired into the 921. if it works. I ordered it from Buy.com, today, and I should have it in a week or so. Thank you all for your expertise. Ed


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## socceteer (Apr 22, 2005)

There is always the option of installing an antenna rotor

http://www.buy.com/retail/product.a...9520&Type=PI&Category=Electronics&dcaid=17194


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## JD Robinson (Nov 13, 2004)

jackson3 said:


> Thanks for all the good information. There sure are a lot of knowledgeable people on this thread. I even got an education on why WTAE (ABC) is located away from the other channels in Pittsburgh. I did try and move my Channel Master up and down and back and forth on the antenna mast but that didn't help with ABC. I'll give the Zenith antenna a try, with an A/B switch wired into the 921. if it works. I ordered it from Buy.com, today, and I should have it in a week or so. Thank you all for your expertise. Ed


Ugh. Rotors. Switches. Can't put THOSE on a timer!

We have a very similar situation here: ABC is 140 deg. off the other stations from my house. Because I don't know any better, I did something silly that turned out to be a great solution: two directional UHF antennas on the same mast, two 300-75 ohm baluns and a cheap 75 ohm coax splitter wired backwards so it's actually combining (I guess) the two signals.

I'm sure someone with more knowledge about the science behind RF will explain why this is a really bad idea, but it works great for me!


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## GravelChan (Jan 30, 2005)

JD Robinson said:


> Ugh. Rotors. Switches. Can't put THOSE on a timer!
> 
> We have a very similar situation here: ABC is 140 deg. off the other stations from my house. Because I don't know any better, I did something silly that turned out to be a great solution: two directional UHF antennas on the same mast, two 300-75 ohm baluns and a cheap 75 ohm coax splitter wired backwards so it's actually combining (I guess) the two signals.
> 
> I'm sure someone with more knowledge about the science behind RF will explain why this is a really bad idea, but it works great for me!


It it works I'd say it's a good idea. I don't think it's generally a recommended pratice due to multipath etc. However, getting usable signals from stations in different directions is sometimes a try and see what happens deal. I have stations about 170 degrees apart and tried that same setup.
Didn't work for me because 2 of the stations are low power, 60 miles away and combining the antennas lowered the signals just enough that they break up. I'm hoping when they all get to full power that it will work...... Meanwhile, as my stations are nearly 180 degrees apart I might try a good bay antenna with the reflector removed.


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## Michael P (Oct 27, 2004)

If the 2 antennas are just far enough apart from each other you may avoid multipath issues when they are combined. It takes a mathematical genius to figure out the correct spacing, however. There are formulas on the web, but you have to know what "lambda" means (I believe it's the wavelength of the desired channel in meters - not MHz).

As for the "bay" antenna, don't remove the reflector! Those antennas are essentially bi-directional. The reflector side should be aimed at the strongest signal (presuming there are weaker ones ~180 degrees). I was able to help out my uncle up in Detroit with a VHF/UHF combo antenna, I aimed the back side directly at Windsor, Ontario for ch 9, the rest of the Detroit stations were close enough to each other on the "front side" so that he never had to rotate his antenna again.


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## jackson3 (Jan 8, 2005)

Michael P said:


> I own a Silver Sensor, it's great! I use an A/B switch between the Silver Sensor and a rooftop omnidirectional "saucer" antenna which is 20' above my roof. The indoor "SS" gets staions farther away than the outdoor omni . I watched Youngstown stations (55 miles away) last night for the first time (aided by "skip"). I use the SS to get the Akron/Canton "rim-shots" that the Omni misses (skip not a factor here - these stations are in my DMA but there are terrain obstructions that have to be compensated for by moving the SS to a "sweet spot" - a different spot for each station). I use the Omni to get the closest (and most watched stations) and only flip to the SS when I want to watch or record one of the rim-shots.


I received the Silver Sensor, yesterday, and after connecting it, I was able to receive ABC. To my surprise, with just a little movement, I was able to receive NBC, CBS and FOX but not all of them at the same time. I am going to do what you have suggested and connect an A/B switch for ABC off of the Silver Sensor. I'm really surprised that they don't make an antenna that can receive stations in an arc pattern rather than in a, mostly, directional pattern. I guess it has something to do with reflection and bounce. Something that I noticed is that the picture clarity from the Silver Sensor was sharper and more detailed than from my roof mounted Channel Master. Could it have anything to do with the length of the cable from the roof to the 921, about 80 feet? Thanks for your input.


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## bbomar (Oct 18, 2004)

jackson3 said:


> Something that I noticed is that the picture clarity from the Silver Sensor was sharper and more detailed than from my roof mounted Channel Master. Could it have anything to do with the length of the cable from the roof to the 921, about 80 feet? Thanks for your input.


If you are looking at digital channels there should be no difference in picture
sharpness. Either the receiver locks on or it does not, but if it does then
the picture quality should be the same regardless of signal level. A weak
signal or a signal with lots of multipath reflection can cause loss of lock resulting in pixelization or total loss of picture, but not a change in sharpness of the picture. My guess is that the difference you saw was a difference in
the source material at the time you looked.


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