The Curve of the Earth, Deep Fringe

My TV reception problems are not caused by hills but by the shear distance from the transmitter 77.6 miles away. My Antenna is adjustable and I was wondering if I should be pointing it into the sky to get a better chance at recieving refraction signals or pointing it down towards the curve of the Earth ? right now I have it set at 90 degree's.

Mike

Basically the answer is no.

The normal range of a television signal is usually 65 miles max.

Once you go beyond the digital cliff and if you can not get a lock on a signal, then you are pretty much screwed most of the time.

Yes the signal does come from above the horizon, but that signal is also dependent upon a reflection in the Ionosphere and if you do not have the right weather conditions - you will have no signal.

You did not furnish a address so we could look at your reception issues, so there is no way for sure for us to tell you what you need to do.

We would need to have a street address of your location and zip code.

Basically the answer is no.

The normal range of a television signal is usually 65 miles max.



While what you say is usually true, it is not necessarily so for the OP. It depends on where Small Engine lives and from where he wants to receive the signals. You are going a "rule of thumb" and there are a few geographic areas where what you say is definitely not true. I live in one such area now and have lived in another area that was similarly blessed reception-wise. However, without the location information we cannot say for sure, one way or the other.

I was wondering if I should be pointing it into the sky to get a better chance at recieving refraction signals or pointing it down towards the curve of the Earth ? right now I have it set at 90 degree's.


If you are behind a terrain obstruction (and the curvature of the Earth counts too), then it's generally best to point the antenna slightly above the point of diffraction. Most of the signal energy will be emanating from the diffraction edge, so you'll want the center of your antenna's radiation pattern to be focused at that area.

Most antennas have a pretty generous antenna pattern in the vertical plane (like a 30º beam height), so it's not that sensitive to exact aim. The situations where vertical tilt really matters is if the point of diffraction is significantly above or below the normal antenna height (your house is on top of a hill, in a valley, or behind a large local obstruction). I wouldn't worry about vertical tilt unless I knew that the optimum signal source was at least 10º above or below the current antenna's orientation.



The normal range of a television signal is usually 65 miles max.

This is an over-simplification of TV reception. The true range of a TV station is dominated by the height of the transmitter. This determines the distance to the horizon which the transmitter can reach with a straight line-of-sight shot.

For example, Mt. Wilson in Los Angeles puts most of the transmitters in the area at a height of about 6000 feet above sea level. From that vantage point, you can get line-of-sight coverage out to about 110 miles. Try looking up La Jolla, CA on TV Fool (strong signals, LOS path, at around 106 miles away)

There are a few man-made towers that reach about 2000 feet above ground, giving them a line-of-sight coverage of about 66 miles.

For transmitters that are only about 1000 feet up, their LOS coverage only goes out to about 48 miles.

Actual coverage will stretch a little bit past this line-of-sight limit due to diffraction, but it is fair to say that coverage is mostly determined by the horizon distance of each transmitter. And, as you can see, the horizon distance can vary by quite a lot depending how high the transmitter is placed.

There is nothing magic about the number 65. Some situations will do better and some will do worse. It all depends on where the transmitters are installed and what the terrain will let you get away with.

Cheers,

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d03fb51ab18eb51
With the Aug 2009 update channel 6.1/NBC is 80.9 miles from my house and I receive it 98% of the time with a good signal. When the atmosphere is in my favor I can receive the following channels in this order 3.1, 33.1, 45.1 and sometimes 12.1. I'm using a xg91 with a radio shack 60 db (thats what is says on the box) amplifier. I know I should just feel lucky to receive any channels but I am hoping if I can tweak it somehow I could receive a few more in the 98% reception range.

Mike

Ok, let me clarify my answer further.

When ever a transmitter site is within the Canadian Border Zone, the transmitter has to be strong enough to try to service the original territory that was covered by the analog transmitter, but not transmit so far as to cross the boundary into Canada and interfere with their signals.

The way they do that is to limit the height of the transmitter antenna and the power of the transmitter, ok - so when you limit or budget a certain part of your transmitters effective range by reducing the height of the antenna to gain power - Effective Radiated Power, you there by serve as many people in your viewing area as efficiently as possible.

Height equals Gain. The higher you place the stick, the less power you need to use to transmit the same amount of distance.

Back in the days of AM radio, Mexican stations would transmit with as much power as they wanted to - because they did not have anyone to tell them that they could not. A very good example of that would be XERB - Ciudad Acuña Mexico. Probably nobody on this forum has ever heard of a radio station called XERB - but everybody on this forum has heard of a DJ who called himself Wolfman Jack!

Their border blaster signal could be heard over a large span of the United States due to the fact the electricity was cheap and they had no restrictions as to how much power they transmitted with. The transmitter was so powerful that birds died when they flew too close to their tower and they once claimed that a person could drive from Los Angles to New York and never loose the signal. It was the most powerful signal in the Northern Hemisphere.

As I have said before, so I will say again, with a normal transmitter at about 2,000 - 3,000 feet above sea level with say 900 feet above average terrain, your normal signal range is somewhere in the neighborhood of about 65 miles in a free space area when you are in the Canadian Zone - Period.

The earth is round and sooner or later the signal does not have anything to reflect off and travels out into space. Even if you stood on top of a 1000' tower and looked out across lake Huron and could see a tower 1000' tall - you could not see that other tower beyond about 48 miles due to the curvature of the earth and due to the fact that what you see is not the actual image - but is a diffracted image. That the light has bent around the side of the earth far enough to let you see that image and is not the actual image - if you flew or if you were on a boat you would have to make corrections to adjust your coordinates to your heading to keep traveling in a straight line to your destination. If you used the coordinates - compass heading you got the first time you had a visual sighting of the target - you would not find the target when you got there - because it will have moved several miles because the line of sight - visual did not match the actual location of the target = other tower.

When trying to explain a double refraction - the easiest way for me to explain this to you is if you ever saw a double rainbow.

When a ray of sunlight strikes a raindrop, the ray refracts, or bends, at the point where it passes out of the air and into the water of the drop. The angle of the bend is determined by (a) the intrinsic light-transmitting properties of air and water (every transparent substance has its own individual index of refraction) and (b) the angle at which the ray strikes the surface of the spherical droplet – whether, e.g., it hits the drop squarely or strikes a glancing blow off to one side.

Meanwhile, the drop is acting as a prism, splitting the white light of the ray into its component colors by refracting the different wavelengths at different angles: red wavelengths bend a certain amount, orange wavelengths a slightly different amount, and so on, this is called - Dispersion.

Most of the light striking the raindrop passes straight through it and out the far side, but some of it reflects off the rear interior surface of the drop and is sent in some new direction. The ratio of light transmitted to light reflected is, once again, a function of the angle at which the ray hits the surface, this is called - Internal reflection.

When the reflected light exits the drop and re-enters the air, it's refracted and dispersed a second time.

Light rays emitted by the sun are effectively parallel when they reach the earth, and raindrops are effectively all the same shape. So when sunlight shines into a sky full of raindrops, it's encountering millions of tiny, very similar spherical prisms and interacting with each in pretty much the same way: each produces a basically identical pattern of refracted, dispersed, reflected, and re-refracted light in a spectrum of colors. The reflected red light is at its greatest intensity at an angle of 42 degrees from the direction of the sun's rays, while the violet light has maximum intensity at 40 degrees. When you face a rainy sky with the sun at your back you see a ring of red light, forming the outer edge of the rainbow, at 42 degrees from the direction of the sunlight, a violet ring at 40 degrees forming its inner edge, and all the other colors of the spectrum in between. The rainbow is entirely an optical illusion; it changes its apparent position in the sky as you change your vantage point, meaning that no two people are ever seeing a rainbow the same way (and explaining why that pot of gold is so elusive). Also, because the light forming the rainbow is reflected at angles of 40 to 42 degrees, for the most part rainbows are seen only during the hours around sunrise and sunset: if the sun is higher than 42 degrees in the sky the rainbow reflected by the raindrops will be below the horizon for an observer at ground level. You get better viewing at greater altitude, and it's possible to see complete circular rainbows from an airplane.

To make a double rainbows, the ray of sunlight bounces twice off the back interior surface of the raindrop before re-emerging into the air. The second reflection inverts the order of the colors – the secondary violet band forms at 54 degrees, the red band at 50.5 degrees – so the secondary rainbow appears above the primary one, with red on the inner edge and violet on the outer. Because the twice-reflected light has had two chances to be transmitted out the back of the raindrop rather than reflected back toward the observer, the secondary bow is much fainter than the primary and frequently cannot be seen at all; it's typical for a secondary rainbow to be visible only at certain points along the arc.

If the light is strong enough to remain visible after being reflected three times inside the raindrop, an even fainter tertiary rainbow can sometimes be seen (at least in part) above the secondary one, with the red back on the outside and the violet on the inside. And rumor has it that it's occasionally possible to see a quadruple rainbow.

Diffraction is a quantum phenomenon where light waves cancel each other out or amplify one another – sometimes figures in rainbow formation, if the raindrops are small enough, in which case you might get smaller rainbows inside the main bow, you might get rainbows with the red in the middle, it is all dependent on the the atmospheric conditions.

I tried to teach all of you about how signals are transmitted and how the transmission process works and how height equals gain and still you get into pissing contests to show people - you are wrong and I am right.

The only reason why the transmitters are up on top of Mt. Wilson and the only reason why the transmitters are so high and the only reason why the transmitters travels to far is due to the fact that for the most part Los Angeles is landlocked.

There is no room anywhere to construct and operate a television antenna site - nor is there people willing to live below a high power transmitter - just as there is very few people willing to live below high power transmission lines - due to the fact that the prolonged exposure to the electromagnetic radiation causes cancer.

Mt. Wilson - is WAY WAY WAY beyond the limits of the Canadian Border Zone and they are allowed more power.

Since the transmitter is higher then the ground below it, it does not cost them as much money - power wise to transmit the same amount of distance.

The height of the transmitter still factors into the distance of line of sight, but as I have said before, once you get so high, it doesn't matter how high you are, your signal will still not travel any further then the digital cliff.

In telecommunication, radio horizon is the locus of points at which direct rays from an antenna are tangential to the surface of the Earth. If the Earth were a perfect sphere and there were no atmospheric anomalies, the radio horizon would be a circle.

The radio horizon of the transmitting and receiving antennas can be added together to increase the effective communication range.

Antenna heights above 1 million feet (1966 miles, or 3157 kilometres) will cover the entire hemisphere and not increase the radio horizon.

Someone here on this forum doesn't understand Line of sight, because physical line of sight is just how far you can see or how far a radar beam can see and that is it.

In my area of the country, when you have a storm and the weathercaster wants to show you how he determined how he made his estimation as to how he predicted what will happen, they show a map of this part of the state and they show a radar beam coming from Cleveland Ohio - Hopkins Airport, a second radar beam coming out of Greater Pitt airport, A third beam coming out of Accuweather - State College / Clearfield PA. Maybe a 4th beam coming out of Morgantown WV and that is it. Each beam over laps the other by a little bit, but no beam has a real effective range of more than 120 miles.

Since Radar is a radio signal, it works the same way as a television signal. If the radar can reach that distance, so can the television signal with the right amount of height and the right amount of power.

But television is broadcast to a certain market and when you get beyond that market, you have to limit the amount of power your can transmit with, or your signal will interfere with a signal 120 miles away. Since you cannot sell groceries or furniture or used cars to a person 100 miles away, that person is said to be in a different market area.

If there is another large town that can support a television station, it is free to open up a television station and can apply for a license to broadcast in that market. The FCC will give it the exclusive rights to that market and they cannot transmit beyond their market, nor can another station in a different market transmit with more power to steal revenue away from the other station.

That is why I said 65 miles. That is usually how far a station will transmit digitally with no issues in a mountainous geographical terrain.

As people in Texas has already taught us, there is people living in Texas who has a antenna, several hundred feet above ground, with nothing between them and the transmitter but cactus and cannot get a signal digitally from 90 miles away that they could with no issues when it was analog. That is because the signal was stronger and was usually on VHF - not UHF and because with analog, even if it wasn't a good signal, there was usually enough signal that you could watch it with some snow and some static.

With UHF digital, it is all or nothing. Either you have a crystal clear picture and sound, or you have nothing.

Good grief!

And nobody in Texas has line of sight at 90 miles.

You are not listening to me.

It doesn't matter what you have, what matters is that the earth is round and the signal only goes so far. Once you get to the edge of the digital cliff, the signal stops bouncing back to earth and travels out into space. Once the signal travels out into space, it is lost forever.

You have a better chance of catching a signal on the moon at the right time of day and month then you do if you are beyond the digital signal cliff.

Instead of acting like you know it all Jim, maybe you ought to reread some of the posts made by forum members from Teaxs and other parts of the country that will tell you that they came here for help. Could not get a solution and had to move on to cable or a dish for their reception needs.

If a person does not have a problem they don't come on the forum looking for help. Period!

It isn't until what they had didn't work and they didn't want to spend any money and even after they spent money could not get the results they were looking for - that they came on this forum looking for help.

Florida, California, Colorado, Washington state, Pennsylvania, New York, Maine, Texas, Illinois, pick a state and we can sit here and talk about it till the cows comes home.

So just to sum it up...

The distance at which you can receive a signal LOS is determined by a conglomeration of:
* The transmitting power,
* The height of the transmitting antenna,
* The height of the receiving antenna, and
* The obstructions that lie between.

To say that height doesn't matter, and there's a limit imposed by the curvature of the earth would be a silly statement. The higher up the transmitting antenna is, the further the signals travels in a straight line. Obviously a transmitting antenna that is at 2,000 ft height above the average terrain will have a significantly larger coverage area than the same power antenna set at 1,000 ft HAAT.

And obviously this distance is effected dramatically by the type of terrain that lies between the two antennas. otaota already said it best, why am I wasting my time...

But I will say I'm not comfortable with JB's use of the term "Digital Cliff" in the previous context. I was of the understanding that the term referred to the power level at which your tuner is receiving a signal, and not to describe how far a signal will travel - Or that once a signal has traveled "X" amount of distance it has reached the "Digital Cliff"... Where one location may be receiving the signal at the digital cliff another further location may be able to receive the signal well within the limit, depending of course on the environmental differences between the two locations.

In the post above I have posted my Tvfool results aka location. Dose anyone have a reccommendation on another TV Antenna system I could try to get better reception in my area so I can receive channels 3.1, 12.1, 33.1, 45.1 and their sub channels on a regular bases.

Mike

Small Engine,
From what you have said earlier, and looking at that tvfool I would say you were already doing incredibly well. But I also see that tvfool report is to the "city" level, and conditions may be considerably different at your exact location.

Do an exact address report, at the actual height of your antenna and repost. If you would like to be even more precise use the TV Maps feature and get the exact coordinates of the antenna on your house and run a report and post a link. (Just move the cursor to where the antenna actually is mounted.)

BTW, to avoid confusion it is usually customary to refer to channels in the "Real" RF ch#, as opposed to the virtual ch# - which means nothing.

P.S. That amp must have a decimal point in there: 6.0dB not 60dB.
What's the model# on the box?

When ever a transmitter site is within the Canadian Border Zone, the transmitter has to be strong enough to try to service the original territory that was covered by the analog transmitter, but not transmit so far as to cross the boundary into Canada and interfere with their signals.

More misleading info. I live in Canada and the stations that I receive with ease from 79.6 miles are all in the USA. What's more, I can receive a strong signal from all but one of those stations with a small unamplified UHF antenna in my ground-floor living room. (The other station is VHF-Hi). The fact is that all of the "full power" Plattsburgh-Burlington stations have all targeted the Montreal area since the first stations in that area went on the air in 1954 and they continue to do so in the digital age. The digital channel assignments made by the FCC took the canadian stations (and their plans for digital broadcasting) into consideration in such a way as to allow the US stations to retain all of their canadian viewers.

A similar situation can be found in the area around Kingston, Ontario (where I used to live) vis-a-vis the stations in Syracuse NY and Watertown NY.

Dang, the Canadians are stealing our ota tv! ;) Just joking...

My TV reception problems are not caused by hills but by the shear distance from the transmitter 77.6 miles away. My Antenna is adjustable and I was wondering if I should be pointing it into the sky to get a better chance at recieving refraction signals or pointing it down towards the curve of the Earth ? right now I have it set at 90 degree's. Mike

Mike, my suggestion would be: if you can do it easily, give it a try! If it doesn't improve your reception, or makes it worse, you can always put it back the way it was. Sometimes, small changes can make a big difference in fringe area reception. I installed a DAT-75 antenna for a co-worker last year, and I tilted his antenna up about 10 degrees, which helped a lot. BTW, he is over 70 miles from the towers.

And, for the benefit of anyone searching this forum for info on long distance digital reception, don't be discouraged by the preceding gloom and doom "digital cliff at 48 or 65 miles" posts. I am 65 miles out from 1000' towers, and I get very reliable reception on both VHF and UHF stations. Not 100 percent, but way better than the expectations I had five years ago when I got my first HDTV and began experimenting with fringe digital reception. At that time, everything I read (including this forum) said that the absolute max distance for digital reception would be about 50 miles. So, I thought buying a new HDTV with a digital tuner could be a big mistake. Fortunately, as is often the case, the pundits were wrong. Even with the old antennas I had then, I was getting better reception on a couple of the digital channels, than their analog counterparts. With improvements I've made, it has only gotten better. So long, analog.

Dang, the Canadians are stealing our ota tv! ;) Just joking...

Hey Rick!
Are they allowed to do that?:D

Dunno, hmm, time to call in the FBI, CIA, HLS, EPA.... LOL! We need to get some shekels from the Canadians to pay off our deficit! :D

Very funny Rick!
And this gets us onto a fresh page - WHEW!:D

The Radio Shack Amp is a catalog # 15-2507 and of course I cant find the box now ! I tried looking the info up on the RS web site and they dont offer/show it anymore, I'm sure I made a typo by saying it was a 60 db amp, its probably more like a 10 db. As far as my Tvfool results I am not sure why they say city level because I live in the country and the closest house to me is aleast a 1/4 mile away. My antenna is at 27 ft. I will try your suggestion in tilting the antenna up or maybe down alittle and see if it makes a difference. There is only one odd thing about my set-up, it points to 166 degrees and that puts the aim of the antenna straight through two high voltage wires coming into my house from across a open field. Canadians that feel quilty about receiving Free OTA from the US can send your checks to 1516 hwy 24 W De Queen, Ark 71832 ;)

I did a google for your 15-2507 amp and came up with your thread from 4/16/09:
http://www.highdefforum.com/local-hdtv-info-reception/93181-radio-shack-15-2507-high-gain-signal-amplifier-review.html

It would appear that is a 30dB amp with (as TigerBangs puts it) between 6-7dB noise factor, which is pretty high. Changing up to a Winegard amp with less than half the noise level (2.8-3dB) might well give you better results.

Do you have very long cable runs or multiple splitters involved?

I really am curious to see an exact location tvfool from you though.

aka.Hooper
Thanks for taking interest in my antenna delima. Here is the radar plot from TV Fool. I have one TV and no spliters, the coax comes straight from the antenna pre-amp and into the amp.. roughly 60ft long. There is not a cloud in the sky and i am watch #15 clear as a bell, other channels are pixilating tho. My xg91 is working as exspected but I was wondering/hoping if I went to a 8 bay antenna if I could get a solid signal on the other channels broadcasting from that same area.
any help from anybody would be appreciated

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d507cc980fec788

Mike

Honestly if it were me I'd change out that amp for something with a much lower noise level first and see how you do. You don't have much cable to make up for, so it's really all about the noise floor.

Bay antennas generally have a wider beamwidth than a 91XG and thus are subject to greater multipath interference - especially important when going long.

I'm certainly not the most knowledgeable source on here, but I would guess with a good amp & aim you'd have a shot down to KTBS 28 and maybe even KMSS 34 on good days.;)
I know, I know, they're just too far...
And the Bumblebee isn't supposed to be able to fly either.:D

If the amp didn't get you there another option may be to get a second 91XG and stack 'em.

It seems to me, that small engine has asked an honest question, namely will tilting the antenna upward bring better reception in a deep fringe situation? Which is something tigerbangs has advocated in the past.

And its all well and fine to apply theory to the question, but at the end of the day, actually trying the experiment in the real world is the final word.

at the end of the day, actually trying the experiment in the real world is the final word.

NonMcTubber is right. Tilting the antenna is a no-cost option to try. It might help, it might not. Either way, you have one more data point to work with. It doesn't hurt to be cautiously optimistic.



I was wondering/hoping if I went to a 8 bay antenna if I could get a solid signal on the other channels broadcasting from that same area.

The XG91 has its highest gain at upper UHF and then gradually less gain at lower frequencies. Some of the 8 bay antennas will do better than the XG91 on lower UHF channels. However, I don't think the difference is big enough to justify replacing the XG91. The 8 bay antennas are bigger, heavier, and more of a wind/snow/ice load than the XG91.

You can probably get more gain overall by doubling your XG91 antenna. This would get you about 2.5 to 3 dB of gain across the board. There's no way to tell how much of a difference 2.5 dB will make, but it might help stabilize some of your marginal channels or get you an additional channel or two.

Cheers,

My TV reception problems are not caused by hills but by the shear distance from the transmitter 77.6 miles away.

The "digital cliff" statement cannot be universally true. We get one at times that is 160 miles, and two consistently that are 104 and 125 miles away.

I put up a new antenna on the roof at a house I own in northern Michigan this summer (just below the big Mac Bridge). No big hills around, so bascially earth-curve and lots of woods are the only issues. House is single-story and antenna is about 20' from the ground.
Antenna is a Winegard 8200 and preamp is a CM7777.

When installed it, the leaves were still on the trees. I'm sure now, reception, if anything, is better .

We get three channels that are 65-75 miles distant and two much further.

One is VHF digital channel 9 with WWTV & WFQX at 104 miles away.
The other is UHF digital 22 with WNEM at 125 miles.

Note that WNEM at 125 miles is one of our stronger channels. TV Fool shows it with a noise-margin of minus 32.4, but in comes in better than a few others that are only 40-60 miles away.

Also, besides the ones I've mentioned that work cosistently, we sometimes get WDCQ on channel 15 that is 160 miles away. Oddly, we only get it on our Sansui digitalTV and can never get it only out other older TVs that use digital converter boxes.

Totally Clear Sky Today.
4:30 CST
Used compass to point antenna to 161 degress, Channel 15 signal strength 64%, 4:45 CST lowered antenna to roof level to make adjustments, channel 15 went up to 74%. Tilted XG91 two notches towards the sky, still 74%, Raised antenna back up to 27 ft, signal strength stayed at 74%. It seems I have lost a few weak channels but gained KMSS 34. I'm going to leave the antenna as it is till cloudy skies come back and make another report.


Mike

For you to get that signal quality at the distance that you are from the transmitters is pretty remarkable. it's a testament to the quality of the antenna that you are using and your own ingenuity.

Using a low-noise preamplifier like a Channel Master might allow you to gain a few more percentage points of signal quality, it it sounds as if a rotator might also help you.

For you to get that signal quality at the distance that you are from the transmitters is pretty remarkable. it's a testament to the quality of the antenna that you are using and your own ingenuity.

Using a low-noise preamplifier like a Channel Master might allow you to gain a few more percentage points of signal quality, it it sounds as if a rotator might also help you.

I originally had a Radio Shack branded 30 dB amp and it seemed to have worked just as well. Technically, it was an AntennaCraft amp
10G212 rated at 30 dB gain and 3.5 dB noise with UHF. I swapped in the CM7777 and gave the "cheaper" amp to my in-laws that live in Alpena, Michigan. I did not do a close study, channel to channel, though.
I put "cheaper" in quotes, because I paid $69 for that Radioshack amp at a local Michigan store. I later bought several for $27 each under the AntennaCraft brand-name. I bought the CM777 for $52, but wanted it for myself, assuming it's better quality.

The long distances might have something to do with all the Great-Lakes water nearby. Our house in Michigan is only 15 miles from Lake Huron.
We also get many Canadian TV channels from Saute Ste. Marie - maybe 75 miles away.

Here at my house in New York, where I am surrounded by hilltops and trees, with the horizon no further then 5 miles in any direction, I don't get anything beyond 60 miles distant. All my antennas are basically pointed into mountain tops - except for one that does better pointing downhill, to the Interstate highway.

I have one channel (UHF 50) that comes in at 59 degrees (by the compass) in the morning, but at night comes in at 210 degrees. That one is kind of hard to figure, but it must be snaking around hills and trees, and changes course during the day. Also, I have no way of telling how much my antenna is actually receiving from the back-end. Presently using a DB8.

After my last post in this thread the other night the signal strength just got worse and worse.. it was so bad by morning I found myself back on top of my roof putting the antenna back to its original postion so my SO could watch her Soap in the daytime while I was away working (insert man being whipped by woman smlie here) OK OK.

I remembered posting this..
Channel 15 signal strength 64%, 4:45 CST lowered antenna to roof level to make adjustments, channel 15 went up to 74%.

So in the next few days I will lower the XG91 and reverse the bracket so I can point it down towards the curve of the earth and see what happens.

I do have a question for tonight tho,, stacking XG91s would you come off one 91 with a 75 ohm converter into a short coax back into a 75 ohm converter to the other 91, then come off the last 91 with another 75 ohm converter then to the coax to the house, or would you just strip the ends off a short peice of coax and just connect the two antennas ?

Mike

I do have a question for tonight tho,, stacking XG91s would you come off one 91 with a 75 ohm converter into a short coax back into a 75 ohm converter to the other 91, then come off the last 91 with another 75 ohm converter then to the coax to the house, or would you just strip the ends off a short peice of coax and just connect the two antennas

No, on both counts.
In order to get two antennas to combine you need have them on the same aim, and position - receiving the signals at the same amplitude. Use identical baluns, and two short pieces of cable into a [decent quality, i.e. 0.5dB max insertion loss] 2-way splitter as a combiner, and then into the amp, etc. The cables MUST be EXACTLY the same length: It's all about phasing - if the antennas aren't in-phase they cancel each other instead of combine. Keep this in mind also... if the signal doesn't seem stronger at first, flip one of the baluns on ONE antenna to correct a 180* phase imbalance. You may also have to play a bit with the mounting distance between the antennas and the height to get them receiving at the same levels, (and in-phase) but once you find the sweet spot I would think at your signal levels getting 2.5dB more gain should be significant.

After my last post in this thread the other night the signal strength just got worse and worse..

. . . stacking XG91s would you come off one 91 with a 75 ohm converter into a short coax back into a 75 ohm converter to the other 91, then come off the last 91 with another 75 ohm converter then to the coax to the house . . .

No, that would be hooking the pair in series. You want to mount them pointing in the same direction and around the same plane and have a joiner equidistant between them - i.e. mid-way. Each piece of coax that runs from each antena to that joiner should be of identical make and length.
Than, from the output of the joiner - you run coax to the preamp.
Use a low-loss combiner/diplexer. There are, or were, some specialty combiners that supposedly eliminated phasing problems. No longer available in the USA, but Triax still sells one in England. The USA version was the Lindsay Stripline Combiner. You can use a common $3 diplexer and probably be fine. Winegard makes a fancier one that has a plastic case and mast -mount for $12. Sold as Antenna Coupler CC-7870.

Note that you can stack vertically, or horizontally. Depends on your area what will work best. If stacked vertically, some have reported tilting one antenna slightly instead of having both parallel.

If you're in a fringe area and gettting signals from way over the horizon, signal direction likely varies, all day long. You could go up on the roof and adust for best signal, and half an hour later it could change. That's especially true is you're in a hilly area.

Also intalling now, with the leaves gone (assuming you've got trees), makes it more likely that what you do now, might not be so good once summer comes.

It's been my experience that, in your situation, no amount of reading specs is going to guarantee your sucess. Read, make an educated guess, and then experiment. I've been doing it all summer in my fringe area in the hills of New York. Also in northern Michigan. I've used every preaamp on the US market, along with almost every well-known antenna - including the 91XG, 9032, HD8200, VIP-307, and DB8. For me, on our worst UHF channels that are blocked by mountain-tops, the DB8 has worked the best. Considerably better than the 91XG. But, that doesn't mean it would work better for you.

I'll add that some people have posted problems with fringe channels using Channel Master 7777 amps. They changed to the ultra low-noise British amp and reported a substantial improvement. I haven't done it myself yet, so can't report about my own experience. I have one on order. But, even if it works better, it's still an anecdotal event.
I also did two hookups in Michigan with one pixelating channel using CM 7777 amps - and improved by using an Atennacraft, higher gain and noise amp. I have no idea why it works better that way, but in those situations - it does. That again in a fringe area, in locations sitting in a hole surrounded by hills. I swapped amps many times over a course of a month, and kept getting the same results. Like I said, results in specific areas, and over time, can vary a lot.

The answer to the succcess that you found using the AntennaCraft amp prpobably lies in signal overload: chances are good that you have a local TV or FM station that could be operating nearby that is causing the 7777 to overload. With digital TV, it's very hard to tell exactly WHAT is causing a station to pixellate, but overload is a much more likely scenario than the difference in gain between the two preamplifiers.

The answer to the succcess that you found using the AntennaCraft amp prpobably lies in signal overload: chances are good that you have a local TV or FM station that could be operating nearby that is causing the 7777 to overload. With digital TV, it's very hard to tell exactly WHAT is causing a station to pixellate, but overload is a much more likely scenario than the difference in gain between the two preamplifiers.

Normally, I would of thought the same thing. but I don't believe that is the situation here.

The signal is very weak, i.e. no TV reception without an amp. With the CM7777, the picture pixelates off and on, and freezes once in awhile. With the Antennacraft- it works perfectly. And . . . the Atennacraft amp has gain-control. If I turn it down just a little, pixelization begins. If the signal was overloading, the opposite should happen. Both amps also have FM traps. The signal-strength meter is always in the lower "third." It's at my wife's parents house, and their signal meter has three sections. Weak, good, and strong. Signal is always in the weak-to-just-barely-good range. Note, this is only happening on one channel - RF 24 in Alpena, Michigan. The Antennacraft amp has 29 dB gain on UHF, whereas the CM 777 has 26 dB. That extra 3 dB of gain seems to make the difference, even though there is more noise.

The more I read.. the more I learn..

"noise" in lay-mans terms.
2 to 3 db of noise is like having 2 to 3 goal keepers stopping the signal from being received, 7 or 8 db is like having 7 or 8 goal keepers stopping the signal from being received..
So the less goal keepers you have trying to stop your signals the better odds you will have of receiving better reception. Right ?

The only way I can justify buying another pre-amp is to hook up my lil Mighty Radio Shack R-75 Cat#15-2160 antenna and dial in channel 15. Then get a new low noise pre-amp and a seperate pole with rotor and try my XG91 from another close location from my house. I have saved a bundle of money by not switching over to a satelite company, that I can afford to experiment some more :yippee:



Mike

"noise" in lay-mans terms.
2 to 3 db of noise is like having 2 to 3 goal keepers stopping the signal from being received, 7 or 8 db is like having 7 or 8 goal keepers stopping the signal from being received..
So the less goal keepers you have trying to stop your signals the better odds you will have of receiving better reception. Right ?


Seems that may not be entirely true all the time. What is more effective? 30 players trying to break through 3 goal keepers, or 22 players trying to break though 2 goal keepers?

There are high gain amps with 3.5 dB noise figures, and lower gain amps with .5 to 2 dB noise figures. Sometimes those ultra-low noise amps make a big difference, and sometimes cheap high-gain and higher noise amps make a big difference with some channels. TV tuners work with a signal-to-noise ratio, and not all tuners reject or accept the same.

I do have a question for tonight tho,, stacking XG91s . . .

We had a nice day here yesterday, for a change. Had maybe 12 hours of "Indian Summer" and temps went from the 30s to 50s F.

So, was able to take my big backhoe, 40 foot ladder, and gear up on the hill top to work on my new antenna site. I mention this because I'm in an extreme-fringe area, and am surrounded by mountain-tops all the way around. So, all my signals have to come over those tops before they get here.

I spent a day, installing a new 30 foot mast and pole. I then installed dual XG91s, stacked and combined. I tried just about every different angle and tilt imaginable, along with three different preamps and two different combiners. Also tried a 24", 36" and 48" boom spacing. I did channel scans throughout the process and also checked signal strength along the way. Tilting up and down, below and over the horizon changed nothing.

Results in brief? Seemed to gain nothing overall, as compared to a single XG91. Single antenna worked consistently, but when duals were installed - it took fine adjustments to get back to what the single antenna did. I find that disappointing.

I also tested several amps on channels 24 and 50 - that were pixelating, now and then. Changing between the CM7777, Winegard 8275 and Antennacraft 10G212 made no difference - except signal strength was strongest with the Antenacraft. Switching FM traps on and off also made no difference. Also, off and on -and only with the Antennacraf amp - I was getting Channel 6 VHF with the XG91s. Since signals change every minute, all day long - I can't be sure what really happened until such results get repeated many times - and I'm not worried about VHF testing with UHF antennas.

At the time the signal was pixelating with the XG91s, it was coming in clear and steady with the DB8 nearby. I had a two-way radio and had my wife watching TV on the same channel back home. So, every time it was breaking up with the XG91s - she'd report the status of the DB8 setup.

I DID encounter one thing though - and I'm usure if it's a gain of some sort, or not. After installing the dual XG91s - I gained a channel I've never gotten before. Channel 43. When I got back home and turned on my TV that is hooked to a different antenna (DB8) - and scanned - it TOO now got channel 43. So, it seems at the moment that installing the new dual XG91s - somehow resulted in a non-intentional repeater system? The dual XG91s are 150 feet further up the hill from the other antenna site, and closer to the signal source. Then can "see" each other though.
If the weather ever gets better again, I am going to take those antennas down, and see if I then lose channel 43 at home via the DB8.

Next experiment is - I'm going to try mounting the dual XG91s side-by-side, instead of vertically stacked. I doubt it will change anything, but I'd like to find out for sure. So far, I am sold on the DB8 for my particular, fringe and non-line-of-sight signal problems on UHF.

The answer to the succcess that you found using the AntennaCraft amp probably lies in signal overload: chances are good that you have a local TV or FM station that could be operating nearby that is causing the 7777 to overload. With digital TV, it's very hard to tell exactly WHAT is causing a station to pixellate, but overload is a much more likely scenario than the difference in gain between the two preamplifiers.

Preamp overload is very common, but not in Worcester, NY. I suspect that the actual noise figure of the Antennacraft amp is lower than the spec sheet. Yet they may vary from one amp to another.

Horizonal stacking of the 91-XGs will get you a much narrower beam so your aim will have to be more precise than with the vertical stack. The vertical stack narrows the beam width in the vertical dimension, horizonal stack narrows the beam in the horizonal dimension.

Preamp overload is very common, but not in Worcester, NY. I suspect that the actual noise figure of the Antennacraft amp is lower than the spec sheet. Yet they may vary from one amp to another.

I did more fooling around today. For the first time ever (here) I actually did get an signal overload on Channel 6 WRGB. That, after I got done fixing up my Wade VIP-30, and testing it on site with the Antennacraft amp. By testing on-site, I eliminate over 350 feet of coax and a splitter. With the amp set at "full gain", it started to pixelate a bit, and as soon as I dialed back the gain-control, it cleared right up. Tried it several times during the day with the same results. Funny thing is - it showed about a 3/4 signal on the meter which usually is not an issue. I've had other channels the pegged it and picture was fine. At the same time, when I turned down that gain control, I'd lose channels 8 and 12.

By the way, the comments Tigerbang made about my VIP-307 wound up being 100% correct. When I installed the other half of the antenna (passive -front), it made a big difference with channel 12.
At this point, I am amazed at this antenna for VHF reception. Especially considering it's been laying in my dump for over 20 years.

Funny thing is - it showed about a 3/4 signal on the meter which usually is not an issue.

That's because the meter is a signal quality meter, not a signal strength meter. The slightly lower quality on 6 may be multipath or interference.

I was able to finish my testing of the XG91 by tilting it upward and downward from the 90% angle setting over the last week to adjust for the curve of the earth. Just as jdemaris did, I measured my signal thru the feature on the converter box and a visiual of the channel itself, the XG91 seemed to preform best at 90%. I have seen several mounting styles of the XG91 to the pole, the manufacture shows the pole going all the way up past the XG91, but there is no mounting brackets for the top boom to the pole provided in the box ?. I mounted mine on the very top of the pole and it seems to be sturdy enough. My final test was to connect the U-75-R Radio Shack 17 element Yagi Style antenna up and see what it could do. The 75 blew the 91 out of the water when it came to getting and holding UHF channels with no pixilating or dropped signals. I still beleive that the 91 is a better antenna than the 75 but I need to do more experiments with the 91, maybe relocating it and using a lower noise receiver and a rotor :busy:

Mike

. My final test was to connect the U-75-R Radio Shack 17 element Yagi Style antenna up and see what it could do. The 75 blew the 91 out of the water when it came to getting and holding UHF channels with no pixilating or dropped signals. I still beleive that the 91 is a better antenna than the 75 but I need to do more experiments with the 91, maybe relocating it and using a lower noise receiver and a rotor :busy:

Mike

I've got a Radio Shack 31 element, 81" boom VHF/UHF antenna that I've very impressed with. For a smaller antenna, I wasn't expecting much - but it works very well and also has great build quality. Radio Shack 15-264 - I bought it my wife's parents in Michigan. I installed it their attic and it worked just as well as several other antennas that were much larger (including a 9032 and XG91). They only have two channels available though, and only one is UHF on RF 24 - so it was not a fair test of the large UHF antennas. The Radio Shack antenna looks like it might be an Antenna Craft HD850, but I'm not sure.

I'm not at all impressed with the XG91 antennas; at least not yet. I only bought them (a pair) because of the many good posts I've read, and also several computer-modeled gain tests posted all over the Net.

I realize that conditions and results can vary greatly, and I'm keeping that in mind. I'm in an extreme fringe area, surrounded by mountain tops. Signals are not coming line-of-sight from the transmitters.

So far, with every test I've done, on average, the Winegard 9032 and the DB8 have beat the XG91s. The 9032 and DB8 even beats the XG91 on channel 55, where the XG91 is supposed to excel.

I'm being stubborn, and trying to believe that . . . if so many like the XG91, then it must be capable of doing better in my situation - if done right. I've already tried a single XG91 at all possible angles and tilts. Also tried a pair stacked vertically, gain with every possible angle, tilt, and boom spacing. The stacked XG91s don't do as well as a single 9032 or DB8.

What I haven't tried is stacking side-by-side. I just read some tests done by two people in fringe areas. Both did what I did and gained nothing with the XG91s until put side-by-side. Then the pair worked better than just one.

I also found one person that tried a single, then duals stacked both ways - and gained nothing. He then stacked vertically, but with one a foot forward from the other - and he then claims to have gotten a 10% better signal.

Who the heck knows? One thing I DO know for sure is . . . the computer models and company posted gain charts don't always reflect real-world installations.

I'll also add that I was surprised how cheaply and light the XG91s are built. The Winegard 9032s are built like tractors, when compared to the XG91s. Obviously, it doesn't matter as long as both can take the wind, but again, I was still surprised. If fact,with just the single mount the XG91s barely sit straight on the boom. The box they came in says an extra optional mount is available, and I think they need it.

If the weather clears up today, I will be stacking my XG91s side-by-side. I'll repost with results if I don't kill myself.

Here are some photos of some of my "experiments." Photos of installaing #1 with a Winegard HD8200 mounted on my solar-panel barn facing the valley. Installation two half way up the hill with a Wade VIP-307 mounted under a DB8 facing the mountain tops, and installation three is even further up the hill - where I'm stacking XG91s. When all done, if things work, there will be six antennas on that mast. Two pairs of stacked UHF antennas and two separae VHF antennas (low band and high). Two XG91s, two 9032s, a Antennacraft Y10-7-13 and a Winegard YA-1026. All about 550 feet from my house, run via some RG11 waterproof coax, put into PVC conduit and buried.

I'm not at all impressed with the XG91 antennas; at least not yet. I only bought them (a pair) because of the many good posts I've read, and also several computer-modeled gain tests posted all over the Net.

Some thoughts about your observations:

Don't trust what you've read on the Internet, you're trying for a bounce shot while most others are using a knife edge.

The pictures indicate that the vertical stacking distance may be a bit to close.

You may discover that it's not the signal strength that matters, but the reduction of multipath. An pair of antennas stacked horizontally will have a narrow horizontal pattern and less multipath than a pair stacked vertically. There has been little work done on the best stacking configuration for bounced signals.

To me, your work is groundbreaking. Keep it up!

Don't trust what you've read on the Internet, you're trying for a bounce shot while most others are using a knife edge.

The pictures indicate that the vertical stacking distance may be a bit to close.


I don't trust anything I see on the Net unless it's a primary document of some sort. But, with trial-and-error, and verification, there are good ideas to be found.

I tried just about every stacking-distance between booms possible from the two antennas touching to 48".

I made some special brackets today so I could mount those XG91s horizontally. Now I've got something ! Works very well, but I want to wait a few days and see if this sucess is consistent. I tried spacing the booms 24", 32", 36", and 48" and, for the most, it didn't seem to matter much, except the lower channels 26 and 29 got a bit stronger when spaced at 32" - so there I left it. I have them aimed just a bit over the mountain-top. When I had only one antenna hooked, two channels were pixelating a bit. When I hooked both, they came in steady.

I then starting working on the next stack, since I'm trying to beat the ice and snow and extreme wind. Got dark just when I got the dual 9032s in place - but I did one test, and for now - they're not working very well.

What you said about the multipath must be correct, since stacking horizontally worked out much better then vertically.

Got dark just when I got the dual 9032s in place - but I did one test, and for now - they're not working very well.


The horizontal boom on the 9032 is directly mounted on the boom while the 91XG is offset. The direct mount may interfere a bit more with the directors.

It is best for the horizonal boom to be fiberglass or PVC or some other non-metallic material, as your is the horizonal boom is part of the antenna, you do not want that.

Mike, my suggestion would be: if you can do it easily, give it a try! If it doesn't improve your reception, or makes it worse, you can always put it back the way it was. Sometimes, small changes can make a big difference in fringe area reception.
Exactly!
Today I reversed the antenna's , putting the U-75-R on the top at 27ft and I put the XG91 at roughly 23ft. Currently I have the XG91 hooked up and I am receiving the strongest signal ever from KTAL/NBC out of Shreveport La. I am also getting fairly strong signals from other stations !. I have been watching KTAL(only) for 20 years except when I was on a Dish ( I miss the Man vs Wild series tho :crying: ) I like NBC for my local news and weather..plus Law and Order, Jay Leno and even the Biggest Losers but the rest of the fall line-up I dont really like and thats why I am here to ask advise and post results. Its very possible that I have hit a Sweet Spot in my antenna location, and now I think I have picked-up a few more channels to get a varity of choices in available channels.

Mike