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Old 14-Oct-2013, 3:13 AM   #1
niteowl
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Low signal strength, and recommendations for an antenna?

Greetings!
Before we get started, please take a look at my signal analysis.
http://www.tvfool.com/?option=com_wr...46ae2c11abd1f4

Iíve been working to improve my OTA signal with an antenna I found in my attic.
http://forum.tvfool.com/showthread.php?t=13686

My first attempts were an attic mount, but we all know this is a less than ideal location, so it was relocated to my rooftop atop an old Directv mount on a 5ft mast, and pointed using a regular magnetic compass. This clears the peak rooftop, and more importantly leaves plenty of breathing room for the antenna in the direction that the signals are coming from:


The arrow shows the direction of 300* magnetic azimuth and the placement on my rooftop. I chose to set it to 300* to ďsplit the differenceĒ between channels (13 & 21) and (38 & 44). The antenna seems to pick up channel 19 off the back just fine.

Now hereís my problem. When the antenna was in the attic, I had issues with a weak signal (30-50) and fluctuating SNR #ís for channels 38 and 44. I figured it was multi-path effects from being in an attic.

After mounting it outside, much to my surprise, Iím experiencing the exact same effects. Except now I donít see the fluctuating SNR #ís as much. Bottom lineÖ Iím having issues with channel 38 and 44. Iím starting the think that maybe this antenna wasnít designed to see much past 600Mhz? As this is where those two channels are. Or perhaps my antenna doesnít have the gain that I require?

The other channels show a fairly decent signal, with good error free SNR #ís
Channel 13 = Signal Strength of 60-70
Channel 21 = Signal Strength of 90
Channel 19 = Signal Strength of 50-60

I have brand new RG6 cable running from the antenna, down about 25ft to my basement. Here a PCT-MA2-4P splits the signal to 2 TVís. One follows a 50ft run of RG6, and the other follows a 50ft run of RG59u. The signal meters on both TVís show consistent #ís of one another.

Any advice for my current setup?

Any advice for another antenna with more gain that will pick up UHF from both directions, and the VHF channel 13? I have a 2ft section of 1.5Ē outside diameter mast for mounting.

Thanks for your time.
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Old 14-Oct-2013, 8:29 PM   #2
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The UHF antenna shown in your first thread may be a 'cut-channel' design, meaning it was optimized for a single channel. If that was the case, it would still make a pretty good UHF antenna but could have poor performance at particular frequencies.

Have you experimented with alternate locations that avoid trees?

Failing that, consider trying a Winegard HD7694P pointed at about 300į. It has more gain than your TVFR suggests is needed, but I see trees.
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Old 14-Oct-2013, 10:18 PM   #3
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Oh yes, the trees. I forgot to mention them, but they can clearly be seen in the photo. In the current configuration as stated above, my antenna is pointed smack dab into the middle of a tree which is about 50 yards away.

Any placement of the antenna on my house is going to unfortunately point at trees on the boulevard either on my side of the street or the other.

I have entertained the idea of aiming the antenna through a gap in the trees which would roughly sit at about 330* This of course takes me further away from channels 13 and 19, but those do have the strongest signals. It would also throw off the angle for channel 19 on the back end. I'll give that a try when the rain stops here.

If that doesn't work, then I think i'll need to change antennas to something more accommodating to the frequencies that I need, with perhaps a bit more gain like the Winegard HD7694P you suggested.

When I look at the specs for the HD7694, it only shows a UHF range of 25 miles. I'm assuming this is just a guideline? Channels 19, 38 & 44 are all over 30 miles away. When I read some of the reviews, people seem to be pulling in channels further away than what it's rated for.
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Old 15-Oct-2013, 12:07 AM   #4
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Pratical and Useful Information.

I agree with the Winegard HD7694P antenna.

I see trees to the , North West.

As always , trees and tree leaves , plants and plant leaves , have a Negative Effect on Broadcast Tv reception and so do buildings and other obstructions including your own roof and house.

Multi-path reflections.

Absorbing , Blocking , Broadcast Tv reception.

The Best Pratice is to install the antenna at a location and height that has the least amount to no amount of obstructions of any type or kind in the directions of reception including your own roof and house.

Digital Broadcast Tv tuners can develop -Digital Glitches- that are not cleared out with simple channel scans.

Do Double Rescan , http://www.wchstv.com/DoubleReScanAlert.pdf.
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Old 15-Oct-2013, 1:39 AM   #5
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Quote:
When I look at the specs for the HD7694, it only shows a UHF range of 25 miles. I'm assuming this is just a guideline? Channels 19, 38 & 44 are all over 30 miles away. When I read some of the reviews, people seem to be pulling in channels further away than what it's rated for.
If not for the trees, I was thinking of an even smaller antenna... Your TVFR indicates LOS paths for each of the top six digital listings. The noise margins are all better than 30 dB above the theoretical minimum needed for reception. The gain of the 7694 adds to that margin.

Finally, 'mileage' values are the product of the marketing department, not the engineering department. Winegard is being conservative, not trying to hype the capability of their product. (This is one of the ways they've earned my respect.) (But when you see claims of 150 mile range, you're in the company of very dubious characters, willing to say anything to get your money.)
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Last edited by GroundUrMast; 15-Oct-2013 at 1:42 AM.
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Old 15-Oct-2013, 2:09 AM   #6
teleview
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Antenna height is important for good reliable reception.
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Old 15-Oct-2013, 2:16 PM   #7
niteowl
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I ordered the Winegard HD7694P this morning. I figured I can keep moving my existing antenna around, but I suspect that I've reached the design limit of what it's capable of regardless of where it's placed. GUM's suggestion that it could be a 'cut-channel' design makes sense, as I believe it was originally used in conjunction with another antenna I found in the attic.

I'll report back my findings once it's installed.
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Old 15-Oct-2013, 4:14 PM   #8
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Another question.

Do I need to be concerned about the Front to Back ratio of the HD-7694P?

Even though most of my stations are NW of me, I would still like to receive channel 19 which is SE of me. Would this antenna be capable of that, or would it work against me?
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Old 15-Oct-2013, 5:12 PM   #9
teleview
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Directional Tv antennas receive the best at the front of the antenna and then to lesser degree at front angles to the antenna and then to a lesser degree to the back angles to the antenna and to a lesser degree at the back of the antenna.

Directional antennas receive the Least amount of signal directly on the sides of the directional antenna.

The smaller the directional antenna is the less directional the antenna is and receives better at angles and back of the antenna.

The bigger the directional antenna is the more directional the antenna is and less signal will be received at angles and back of the antenna.

Small directional antennas receive less at the front of the antenna.

Big directional antennas receive more signal through/at the front of the antenna.

Small antennas have less metal receiving elements to receive signal.

Big antennas have more metal receiving elements to receive signal.

Antennas of any size , DO NOT Pull In Signal.

Antennas receive the electromagnetic energy that comes in to contact with the metal receiving elements.

-------------

At your location it is important to have the antenna Up High so the antenna can receive more signal that is not blocked and multipath effected by the trees.

Even if can not clear the tops of the trees with antenna mounting height , signal strength gets stronger and mulit-path will likely improve as the antenna goes higher.

The clearer the reception path to the transmitters the better the reception will be.

Last edited by teleview; 16-Oct-2013 at 3:02 AM. Reason: Clarify information and typos.
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Old 15-Oct-2013, 5:13 PM   #10
ADTech
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The FBR is not sufficient to preclude some reception off the back. It not not be reliable, though, depending on what might be in front of the antenna that might reflect signal back to the front of the antenna.

You'll have to try it to see what happens.


Quote:
Even if can not clear the tops of the trees with antenna mounting height , signal strength gets stronger as the antenna goes higher.
Except where the additional height puts the signal path through thicker foliage which will have a greater attenuation and scattering effect on the signals. OTOH, if you happen to be in one of those areas where the signal path is clearer "down low", then that's where the antenna is most likely going to be able to catch signals the best.
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Last edited by ADTech; 15-Oct-2013 at 5:17 PM.
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Old 15-Oct-2013, 7:52 PM   #11
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Quote:
Originally Posted by niteowl View Post
Another question.

Do I need to be concerned about the Front to Back ratio of the HD-7694P?

Even though most of my stations are NW of me, I would still like to receive channel 19 which is SE of me. Would this antenna be capable of that, or would it work against me?
I'm not too concerned about the F/B ratio of the 7694, CH-19 is one of the stronger signals. I'm more concerned with the trees. You're in a situation similar to many others, needing to compromise between several competing factors. The added gain of the 7694 will help with the fixed component of foliage induced attenuation, and off axis multipath. It can't deal with fluctuating component of foliage induced attenuation that can give the tuner equalizer grief.

In a perfect world, you would have a nice tower that cleared all the trees. Then we would be talking about a more compact antenna.
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Old 19-Oct-2013, 4:53 PM   #12
niteowl
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Just thought I'd update this thread. I received the 7694, and got it mounted up this morning and pointed it @ 300*. I played around between 300-320*, but CH19 got worse the further it fell off it's axis.

Some signal stats:
Channel 13: Signal Strength = 90 SNR = 28-29
Channel 19: Signal Strength = 40-50 SNR = 21-25
Channel 21: Signal Strength = 90 SNR = 27-28
Channel 38: Signal Strength = 75 SNR = 27
Channel 44: Signal Strength = 65 SNR = 25-26

Just as expected. Channels 13, 38 & 44 improved, and Channel 19 took a slight hit.

Of course these numbers will fluctuate between day/night, and weather conditions. Just after I mounted the antenna, the wind started to pick up. I was seeing some fluctuating SNR #'s for CH19.

I've humored the idea of mounting that old Yagi below the 7694, and pointing it 120* SE for CH19. Not sure if that would work, or how to do it without the two interfering with one another? Any input on this?

You can see what I'm working against here. This is looking NW at 300*


And the finished product.


I think GUM summed it up best when he said:
Quote:
In a perfect world, you would have a nice tower that cleared all the trees. Then we would be talking about a more compact antenna.
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Old 19-Oct-2013, 5:29 PM   #13
niteowl
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double post

Last edited by niteowl; 19-Oct-2013 at 5:48 PM. Reason: double post
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Old 19-Oct-2013, 5:51 PM   #14
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Quote:
Just after I mounted the antenna, the wind started to pick up. I was seeing some fluctuating SNR #'s for CH19.
Which is exactly as would be expected since the antenna is aimed point-blank at a tree.

Sometimes you just have to take what you can get.
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Old 19-Oct-2013, 6:31 PM   #15
teleview
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When the tree leafs out , reception will degrade , recommend go Higher with the antenna or cut the tree.

Thank you for the pictures.

Makes the point of importance of avoiding trees.
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Old 19-Oct-2013, 11:04 PM   #16
niteowl
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I’m going to have to make the best of what I have now, and maybe try a chimney mount next summer to get things raised up a bit.
Also did some playing around today.
I put the old Yagi back in the attic, and spun it around to 120*SE. Then I used a 3 way splitter to tie in the Yagi and the main line to our primary TV.
Channel 19 Before:
SS = 45-50 SNR = 21-25
Channel 19 After:
SS = 65 SNR = 24-25
All other channels remained the same. I was not expecting that.
Then I tried running the old Yagi through another PCT-MA2-4P, and then to the splitter.
Results:
SS = 70-75 SNR = 25-26
All other channels remained the same for signal strength, but the SNR’s dropped just a hair. The amplifier obviously induced some noise into the system.
I removed the PCT-MA2-4P, and am now just running the splitter. I will try this for a while and see what happens. I suspect once the roof accumulates some snow, things will change drastically again. Not a big deal, as the attic is accessible, and things are easy to change back.
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