Build a Large DB8 HDTV Antenna: Big Bertha

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Introduction: Build a Large DB8 HDTV Antenna: Big Bertha

About: Retired Jr. High science teacher of 30 years. Always into lots of things. Now I seem to be into them more. Love woodworking, guitar, portrait painting, and a lifelong obsession building things. I have rotated…

Update June 2018: Nine years old now and it's still up there. I've checked it out a couple of times and all looks like the day I built it. Some washers weren't galvanized so some rust but not enough to make a difference. A large snowstorm on a steel roof took out the coax as the thick snow slid off the roof. Reconnected now and this summer i'll make a larger offset on the roof edge to eliminate this issue. Same Sony Bravia from the last update and still getting the same stations.

Also, I'm currently completely off any pay per view service like Netflix or Hulu. We still have Amazon Prime for it's other services so it's video is available. I've been using Kodi for awhile now with a VPN to mask my IP address. It's been very good for us. We watch any TV show the next day after it plays and have a choice of all movies made. So, our entertainment bill is essentially down to a high speed cable bill with a Mac mini connected to the TV and an Amazon Echo Dot. These changes along with the antenna for network tv and we're good.

Update May 2015: this antenna was built in 2009. It is now 2015. We still have it and it's still doing it's job. I've since put an amplifier on the mast and we now can get that fringe channel lightly to the left of the others without any longer having to use the rotor to turn it. Actually, I leave it set facing the fringe channel and the stronger ones are the ones that compensate. I go up on the roof to check things every couple of years and so far all is well. I would recommend stainless hardware throughout if doing this. My plated stuff is doing well but stainless would have given many, many years of carefree use. Oh, I also now have a 60" Sony Bravia LED instead of the old Sony analog TV we had at the time of the original construction.

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Original Post

We've had Cable TV and Cable Internet. It seems that there is less and less on cable than there ever was. Cable in my area is $49. I eventually cut down to basic for $20 and supplemented with Netflix. Netflix is excellent by the way but that's another story. We also have my macintosh connected to the TV so we can Hulu any program that played recently.

I'm finding that even basic cable has little 'value'. By value I mean I get the basic local channels and a bunch of junk otherwise. The channels I look at I could get for free if I used an antenna. Hence, I've decided to minimize.

Here in Southern Maine the TV stations are mostly in Portland about 30 miles away. Some are further, about 50-60 miles away. Most HDTV antennas work for 30 miles and a few claim to get up to 60 miles. I decided that I need more antenna than that. Something where 60 miles might be the limit but a doable and good limit. I've decided to produce a DB8. A DB8 antenna has 8 receiving elements, or 4 pairs of elements. It's basically two DB4 antenna's combined. The last picture in the segment is a commercial one.

What follows is my foray into the world of HDTV antenna construction and trying to squeak the most out of it for a moderately fringe TV area I live in.

BTW, the last segment contains all kinds of HDTV signal information and links to places to assist you in learning more. I was a teacher for 30 years (no I don't want any help with my grammar, I said I used to be a teacher) My job was simplification and clarity. I hope this instrucatble is up to that.

Step 1: Plans and Measurements

I want to give credit to this website for the dimensions for the antenna. And the diagrams uploaded as part of this instructable. At the site you can find a bit more information.

http://www.frontiernet.net/%7Emclapp/Antennas/diagrams.html

The measurements should be exact or as exactly as you can get them. I will describe the materials as the steps to building this occur. Most of the actual antenna construction part can be purchased at Home Depot which is where I got the raw construction materials.

The first diagram gives the overall dimensions of one array.
The second diagram shows the wiring and dimensions of the wiskers
The third diagram shows the measurements of the wiring

I suggest you print these three pages.

Step 2: Building the Reflector

The reflector can be made of any metal. You could use a solid sheet but in a big wind it would be a problem. And all that is really needed is horizontal bars or wire that are separated by no more than 2 inches vertically. Anything larger than that and it would exceed the wavelength and would not reflect the signal to the wiskers. I found some 36" wide rolls of something called galvenized wire netting at Home Depot. It's got 1/2 inch squares of stiff galvenized wire that is welded at each crosslink. The 36" is perfect for the width of the array. Wider could be used but it would go wasted as the reflected signal wouldn't hit anything useful.

Unroll 40 inches (for the hight) and cut it with snips. To reinforce the sides (40" side) I used thin 1/4" wide angled aluminum trim. I placed one side of it under the mesh and pounded it over with a hammer.

Picture 2 shows this more clearly. I then turned it over and pounded the other side to flatten the mesh as the aluminum tended to curl in the direction of pounding. Do the same thing to the other side.

4th picture
Next, use two, thick, 1inch wide X 36 inches long aluminum bar to reinforce the top and bottom. As the measurements show the two sides of the array are wings that will be slightly folded in. Place the bar in a vise and bend 10 inches of the bar 2 1/2 inches forward. Do the same to the other end. To assist, make a wedge 10 inches long and 2 1/2 inches wide out of hardboard to act as a guide. Or just measure it. Make another angled brace for the bottom of the array.

5th picture
To prepare to install the two bent top and bottom braces, measure 10 inches of the side of the mesh and bend it slightly on the edge of the workbench. Do the same to the other side.

6th picture
The bar is on the bench with a final angle check. Drill small holes. 2 on each end of the angled bend and one in the center of entire bar. I used 3/4" size 8 machine screws and nuts with washers on each side to bolt the bar to the FRONT of the mesh. Bolt one to the top and one to the bottom.

Step 3: Spline

For all the solid bracing you could use a number of materials. Wood would work but it might rot over time. I chose to use plastic board. It's the stuff they often use to do the eves of houses now. It's white, tough and work much like wood. It's also pretty expensive. It's up to you.

Cut the spline the hight of the reflector (40") and drill and bolt to the top and bottom of the BACK of the reflector. Be sure to use a washer on the spline side. I also used a small lock washer. I expect wind will rock the reflector back and forth and don't want the nuts coming loose.

The pictures below just show three views of this step.

Step 4: Preparing Forward Whisker Brace

The V shaped wiskers will need to be mounted ahead of the reflector. A brace 29" long (the distance from the top to bottom wisker is 27") is made from the same material as the back brace.

Picture 1
Use a large drill (forstner bit works nicely) to drill a recess for each of the eight wiskers. use the diagrams from step two to determine the distance apart they should be. About a 1/4" deep should be enough. Notice that the recess is of the side of the brace. This is to accomodate the wiskers sticking out.

picture 2
Drill the center of the recesses to accept a machine screw.

Step 5: Preparing Phase Line and Whiskers

Phase line: the wires that connect the wiskers together. See the diagram. I used #12 copper house wire.

Whiskers: The wires that produce the V shaped elements. I splurged and purchased some bare solid copper #6 wire off the roll at home depot. I bought 30 feet of it and have about 2 feet left. I bought enough because we're building two of these things here and hooking them together. If you're only building one then 16 feet should be sufficient with a bit left over. I built two so I could connect them together and maximize my signal collection. One of these is good for 30 mile reception.

You can use smaller wire for the whiskers but it might no stay in the correct configuration over time as movement of the antenna might alter their shape.

Use the phase line diagram in step 2 to determine measurements.
I stripped the plastic of the house wire to obtain a length of plastic coated white and black copper wire. I wanted the plastic coating to stay on the wire everywhere except the place where it connected to the whiskers with a screw.

shape the two wires as shown in the diagram. Make loops where it will go under a screw. make sure the loops coincide with the depressions you drilled in the front brace. Be sure to make a loop for the center. This is where the antenna wire will connect when it is mounted on the roof.

Picture 1 and 2
I wanted the plastic insulation off the loops but cutting it off was getting tedious. So, I fired up the propane torch and melted it off. With a little sandpaper the loop came clean.

Pictures 3 and 4
Cut 8 pieces of the #6 copper wire for the wiskers. In the end each whisker should be 9 1/2" long. So cut it the wire 18". I found that an extra inch helped out. You can always cut any excess length off after.
Bend the wire in half around a bolt in a vise. and pound it together, then use pliers to spread the whiskers apart in a V shape.

Picture 5
Seat the V of the whisker in the recess, Place the phase line wire loop over it, add a screw, with washers on both sides and squeeze it in place by tightening the nut. Do the same for all 8 whiskers.

Step 6: Mounting the Whisker Spline to the Reflector

The following pictures are just various views of the same thing. The whisker spline mounted to the reflector. this mounting can be accomplished many ways. You could cut pieces of plastic pipe and use it as spacers for example. I decided to use some more of the plastic board to create a fin between the splines. I thinned it out a bit on my planer (if it looks thinner to you).

It is attached to the rear and front spline with 2 inch galvanized sheetrock screws. 5 or 6 on each side. It seems solid. Be sure to notice the measurement parameters on the diagrams for how high it needs to be raised.

Also notice the whiskers have been bent forwards 2 1/2 inches to coincide with the wings of the reflector. In actuality, this thing could have been made flat. But only the reflector directly behind the whiskers would have deflected a signal to them. The bent configuration creates slightly more reflection and therefore slightly more signal to the whiskers. But not much. Remember, I'm looking for fringe signals. You may not be in that position. Stations might be closer for you.

Step 7: Ganging Two Arrays (optional)

As you can see in the following pictures I created two reflectors to put them together to make an array. One reflector will work perfectly well for up to about 30 miles from a station. Two arrays won't give you double the distance but almost. And I'm counting on the design of these antennas to actually be over 30 miles for one and at least 60 miles for two.

I ganged them together using think 1" aluminum angle bar. I simply drilled and bolted them across the top and bottom of the flat bar braces. I used two screws on each side, so four screws for the top and four for the bottom.

The center of this whole thing is where my U bolts will be placed to mount to the mast pipe. If you use only one reflector then it would go in the center of that reflector.

These reflectors can also be mounted one above the other on the mast but you'd need a longer mast pipe and doing so might facilitate having to use guy wires to steady it in a wind. Alignment is fairly specific for HDTV signals. A bobbing, waving antenna might be an issue.

If you decide to just have one antenna then skip to the section on connecting them. It will be simpler.

Step 8: Connecting Your Antenna Array

Please remember that all connection instructions are your responsibility. If you feel uncomfortable on a roof doing this or with grounding properly for lightning then have it done professionally. Basically this means that I absolve myself all responsibility in this area.

Antenna mast
How you mount your antenna is your business. There are several mounting masts available. I'm mounting mine to my chimney. Using a set of stainless straps that wrap around the chimney for just this purpose. My chimney isn't being used. If yours is, especially for wood or coal I suggest another spot. Your antenna will be soon covered with soot if you use the chimney. Two things are important.

One is that if you can get higher, the higher the better. Mine will be 10 feet above the roof. Remember though that anything much over that should have guy wires to steady it.

Secondly, if the stations are not all in one location, like a city, then you'll need an antenna rotor to turn the antenna the desired direction to the station. See the last chapter of this instructable to find out where your stations are located.

Connecting the antenna
If you just made one antenna then you'll only need the balun, lightning arrestor and coaxial cables. Connect the two leads of the balun to the too center loops of the antenna phase line. Connect with screw, nut and washers keep it loose or drill and bolt it to the standout board if you want. connect the other end to a short coaxial cable. Screw a lightning arrestor to the pipe and connect the other end of the coax to it. The other terminal on the arrestor goes to the TV or DTV converter box.

If you've got two antenna's like I do then you'll have to use to balun's and a splitter (or in this case a splitter acting as a combiner) mounted between the antennas. the diagram should explain this.

I recommend that all connections either be wrapped nicely with electrical tape, or coated with silicon II that hardens (outdoor silicon caulking is fine) or use coax with weatherproof boots on the connections.

Grounding your mast
It is very important that you ground the antenna and mast. You'll need to get a ground rod and connector made for this and a length of aluminum grounding wire. Attach the ground wire to the antenna mast with a screw or clamp and run it to the ground rod that has been driven into the ground. Securely attach it to the ground rod with a screw clamp made for this.

Step 9: Up on the Roof!

This series of pictures just shows the assembled antenna up on the roof.

The first picture shows one of many ways it can be done. I have an unused chimney that is large and strong. I chose a chimney strap system. It consists of two corner brackets and stainless straps that go around the chimney. Turnbuckle type bolts let you tighten it. The mount is strong. You can also get roof mounts in various configurations. One of the best and least invasive are the brackets that mount on the side of a house at the peak. No holes in the roof and you can screw into solid wood.

The second picture shows one half of the array and how the matching transformer is connected. I attached the leads with stainless steel machine screws with washers on both sides and a nut. Then ran the bolt through the white plastic to brace and bolted the connection to it.

The third picture is of the splitter being used as a combiner. A coax from each elements matching transformer is connected here so they antennas can be 'combined' into one cable. This splitter actually degrades a bit of the signal but the second element will bring in enough extra signal to make it worthwhile.

The fourth picture: Bolted to the mast pipe is the coax grounding lug. The short length of coax from the splitter is on one side and the other side is the  coax to the TV.  The ground wire is connected to the lower pipe and goes to a ground rod. There is a grounding screw on the grounding lug that the ground wire can be attached to. My wire is attached to the mast below the rotor.

Here you also see my channel master rotor. Where I am the signals are within a 20 degree arc with some of them being 180 degrees to the rear.

The fifth picture shows the entire antenna from the front.

Step 10: The Visual Results

Note: it's now 2018 and we all should have digital TV's. This converter box part of this is no longer necessary and you should be able to connect directly to your TV.

The digital tv converter box I chose is the Digital Stream DSP7700P Digital Set-Top Box. There are many to choose from. Some have much better reviews than others. But, there are enough horror stories for each box to make you think that all of them will be a lemon. And at this time not many are available since the government coupon deadline is over. This one seems to be working well.

The second picture shows the back of the converter box. Simple really. Coax antenna in and coax out to TV or you can connect your TV via the analog RCA jacks. Your choice. The box has an on button and channel up/down buttons. It comes with a infrared remote that has more bells and whistles. The instructions are sequential and fairly clear. You can see a signal strength and scan for channels that lock in when done. There are full menu items for a variety of functions.

Where I live in Southern Maine there are three locl channels NBC, ABC, and CBS that are 25-35 miles away. I live on a lake and therefore a valley that is low and surrounded by hills. Trees are also all around my house and the leaves are still on them. My antenna is about 20 feet above ground.

There are three public television stations 7-35 miles away and Fox movie station where american idol exists. So, the wife would like to get that. The only problem is that Fox is 62 miles away. Definitely a fringe station.

The closest station NBC has a signal strength of 88-90 and very strong. ABC and CBS have lower but still strong signals. ABC is further away but the antenna is atop Mt. Washington so, a good signal. Picture three shows the signal strength for NBC.

The fourth picture shows the signal strength for Fox at 62 miles away. The signal strength is 30% which is more than enough for viewing. A strength of 5-10 should be enough but with this station at least 18 is needed. With digital signals the picture is usually always good if you can see it. Snow on the screen is only for analog signals. At 18 though some blocky artifacts can sometimes be seen. This signal was supposed to be the litmus test for my antenna. My neighbor with a db4 an amplifier can't get this station.

The last picture is of the trees in the direction most of my stations need to deal with. Trees aren't good but the antenna seems to not be bothered by them. The leaves will soon be down.

Overall the construction experience has been pretty good. I had a lot of fun and learned a lot in the process. I hope the info here is correct. I'm no expert for sure. I ended up getting the three networks and Fox, three public television stations, and a couple of smaller local stations. BTW one of the good ones ABC is a VHF not UHF station. This often requires a VHF antenna. The strong signal along with the strong antenna seems to make this unnecessary. After the weekend I will be giving Cable TV back their signal.

Thanks for reading,
Dan

Step 11: Digital Signal Strength 101

There are tools on the internet to help you determine the stations in your area, their power, distance, and your chances of getting them to show on your TV.

http://www.tvfool.com/?option=com_wrapper&Itemid=90

I suggest you try 'TV Maps' link. Type in your address, height of your antenna and you can determine your chances of reception.

You'll also see a list of stations in your area. If you choose one you'll see a color coded map of signal strength from the station to your location. The list shows the distance in miles and and important number NM or noise margin. The antenna we're making should have a gain of at least 15, hopefully more. Think of the NM as the loss of the signal to your house. It could be hills, leaves, walls or weather. It's also distance and location of you and the signal tower. The goal is to get a net gain of at least 0. At zero you'll get a signal. For a reliable signal a higher number is beneficial. 5-10 means you'll probably get a signal over 0 consistantly.

So, take your antenna gain. Let's use 15 and add the NM For the positive numbers it's no problem. The negative numbers might be another issue. An antenna of 15 db hoping to get a stations that's -11 db leaves a net gain of 4. Marginal but a reliable steady signal is possible at this level. The thing is every splitter, length of cable, branch in front of the antenna, Snow in the air, and many other factors can lower the db of gain bringing that gain of 4 down to 0 or lower meaning loss of signal.

2 People Made This Project!

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221 Comments

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8-12
8-12

Question 8 months ago

do you know how much your 8 bay antenna weighs ??

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8-12
8-12

Answer 7 months ago

I weighed the reflectors that were going to be on the antenna... the combined weight was 8 lbs.. and I estimated the weight of the rest of the components to be around 7 lbs.. now considering the weight and the wind resistance and being on a 60 foot tower, I got a little worried ..I have antenna parts and pieces, and I was thinking of putting a series of 3 ft aluminum elements, spaced 4 1/4 inches apart and 40 inches high for each set of elements as the reflector.. I seen other manufacturers using them as a reflector ( what do you think) thanks for all of your advise G J N g

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deceiver
deceiver

Reply 7 months ago

If I read this right the reflectors are going to be solid and not mess??? If that's so my thinking is that you don't need to do that. It won't reflect the signal any more than a mesh. The wavelength requires no larger than 1" holes in the reflector. Anything smaller than that won't do any more redirecting of signal. So, if you have a 1/4" mesh or a 1/2" mesh there will be no difference. So, I'd go with an open structure to let the wind through. Maybe that's not what your question was?

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8-12
8-12

Reply 7 months ago

no there is no mesh.. what I am thinking about is a series of 3/8 aluminum elements as a reflector it will take about 11 of them that are 36 inches long and 3/8 inch diameter. .like a ladder.. I have an 8 bay winegard 8800 with that type of reflector and I see a lot of them on different antennas this should reduce the wind resistance

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deceiver
deceiver

Answer 8 months ago

No I don't. I brought it up onto the roof myself without much of an issue and lifted the whole pipe with the antenna on it to put in the chimney mount. So, It's not very heavy. Maybe 40 lbs at the most????

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8-12
8-12

Question 10 months ago

I am thinking of making an 8 bay antenna back to back to receive stations in both directions should I put wings in both directions??? thanks G J N

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deceiver
deceiver

Answer 10 months ago

Actually, you can build it back to back using the same reflector. One side won't interfere with the other. Just remember that adding the extra combiners and impedance matching devices will cause you to loose some of the signal strength but not that much really. And if you're stations are not super remote they'll be strong enough to begin with anyway.
On another note, if you put an antenna rotator on the thing you can avoid having to do it this way. They're not super expensive and not that difficult to install. Doing so can also allow you to fine tune the directionality for fringe stations that will only come in if you're pointed right at them too.

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8-12

Reply 9 months ago

I just now did a rescan on TV FOOL and it gives the channel I want as in the red 37.3 miles distant w/NM (db)5.0 and pwr -85.9 and 2 edge I am starting to wonder if my preamp is part of the problem.. my main problem is the raising and lowering the 68 ft tower.. some of my tv fool scans are making me question the results

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deceiver
deceiver

Reply 9 months ago

Well something is up. I'm not sure from the information what it could be. The preamp shouldn't cause any issues if it's working with everything else. With that height and signal strength I'm wondering if there is something that is right between you and the station. Usually it's a hill but sometimes there is a water tower or stand of large trees that can affect things especially if they are wet. I do know that a set of large power lines with towers and such can cause issues too. This stuff has to be directly in line of site between the station tower and the antenna.

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8-12
8-12

Reply 10 months ago

The reason that I wanted to build one this way ,was because I have to scan for new channels when I rotate the antenna. I can't add new channels without rescanning.. also I was going to combine both sides and add an antenna preamp

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deceiver
deceiver

Reply 10 months ago

No, it doesn't work that way. If you were going to make it double sided like the one I have you'd need four in all. They are pretty inexpensive. But like I said earlier if you have fairly decent signal strength you could just make half of the antenna I did but put them back to back. Also, you could leave the reflector flat. It would simplify the build and not affect reception much at all. Flat is just fine.

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8-12
8-12

Reply 10 months ago

right you are I guess that I will have to go back to school and learn how to count up to 4 THANKS ( I feel pretty dumb)

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8-12
8-12

Reply 9 months ago

do you know approx what the gain of your 8 bay antenna might be I am trying to get a station that is only 37,3 miles away with an nm of -15 I have tried an 8 bay winegard hd8800 with a preamp a XG 91 w91 elements and a stellar labs #30-2415 w71 elements and I even bought 2 TA-451C and added about 60 more elements to the #30-2415 all using the rca -1e preamp..I seem to be fishing in the kitchen sink I have a tower that is almost 70 ft and I do get stations that are 86 and 140 miles away the 140 is nice and clear the 86 mile one is in and out but viewable 90%of the time what might I do to lower my NM.. I cant find any info on the antennas as to what their gains might be I feel that your 8 bay will get me closer to that channel ..OH YEA according to tv fool the channel that I am trying to get is in the red and the distant ones are in the grey thanks for your time and input G J N

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deceiver
deceiver

Reply 10 months ago

You should be able to scan for channels in the direction where most of them are then you should be able to manually add the channels afterwards. The scan feature is just so you don't have to go through all the channels by hand to see if they work. That's the way it works on my Sony anyway.

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8-12
8-12

Reply 10 months ago

would I need an impedance matching device? couldn't I just wire both antennas together?

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deceiver
deceiver

Reply 1 year ago

Well, I'd have to upgrade the TV and my 60" Sony is still going strong after a long time. And, I'm satisfied with the 1080 dp. As long as the football score is clear in the top right of the screen, it's all okay with me.
As I understand it, existing digital antennas will work with the new standard. I don't see myself jumping to change though. My entertainment is, locally the antenna, and everything else, the internet. I actually do some dubious things so that I no longer need services like netflix and amazon prime. I have a mac mini dedicated to the tv and we are able to see everything we want to. Actually we can watch anything that exists or has existed. Sometimes we get to see things before they exist. For example of one item we use check your USTVGO.TV You'll see what I mean. All the cable channels online, including HBO, Starz, etc. It's good to have a VPN though. I also frequent torrents. So, whatever we want to watch we can. We just pay for our internet connection and that's it. Unscrupulous I know but....hey.

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travisking1260
travisking1260

Reply 10 months ago

Can I just pay you to build me a good antenna

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deceiver
deceiver

Reply 10 months ago

Ha... afraid not. Thanks for the confidence though. There are some good HD antennas out there on the market of similar configuration.