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Seeking advice on a weekend DIY antenna project

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Old 08-03-2012, 11:18 AM   #1  
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Default Seeking advice on a weekend DIY antenna project

So thanks to aka.Hooper's handy guide to posting help requests I'm going to try to provide as much info as possible so that you guys/gals can give me some advice with regards to the optimum design/specs/materials to use for my situation.

I'm looking at trying to finalize cutting my ties with Comcast by installing some sort of antenna in the attic of our townhouse (which we own if you care). I'd rather not do a mast/outside mount as I hate being on the roof and have no real attachment points. The attic is above the 2nd floor and our roof is composed of normal asphalt shingles. Plenty of room in the roof and I may actually be able to hijack an existing comcast coax line that was previously used for an upstairs bedroom as a line to the downstairs mancave which is the primary TV watching location.

Cost is an issue but I'd rather pay an extra 10-20 bucks to be assured of a good reception pattern for those network stations (I love me some college football and the olympics right now are driving the missus crazy). I'm a moderately handy person and have tools if not a great workspace. I'd also consider making this a fairly permanent install because I can't see it being worth the trouble to pull it down and remove it if/when we move away from here in a few years when the missus is done with her schooling.

Please see attached for the tvfools report for my exact address.

From aka.Hooper's guide to posting, here's some responses

* The approximate length of your cable run(s)
40 feet or so, that's a guess but from attic to ground level. The house is a two story with an attic.
* How many sets you are/intend on serving.
One primary set downstairs, possibly another one upstairs later, no HDTV video cards/capture planned.
* The model #'s of any existing antenna(s)
None, I purchased RCA ANT1450B Flat Antenna With Amplifier from Newegg and could only get PBS without running a coax into our backyard. With that antenna resting on a fencepost 20 feet from our rear house wall I could get a grainy/poor reception of NBC (channel 40 here), I will be returning it to them soon so I'm building the replacement ASAP.
* The model #'s of any amplifiers you are using.
The amplifier that was included with the above antenna
* Your specific geographic/environmental conditions. For instance:
Does your antenna aim point into a stand of Sequoia's, high voltage power lines, or a hill?
None besides normal foliage like pine trees and other houses normal of what one would expect in this region of Florida.
Or are you on top of a hill?
Tallahassee is, in general, higher than the surrounding area but I'm only slightly higher than the surrounding area, not on a distinct hill per se.
Do you have close buildings taller than your antenna height between you and the transmitters?
Quite possibly, but not skyscrapers, just other houses.
Or does your aim point you across a large body of water?
It does not.

Thanks all and let me know if I've missed anything.
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Old 08-03-2012, 11:25 AM   #2  
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Oh, and I have done some basic research into what options I do have regarding array's/relfectors/what a balun is/etc, I didn't want y'all to think I just jumped in here to ask without having done some due dilligence.

I didn't mention any of my thoughts/plans because I didn't want to taint the source with any faux pas on my part. I'd just really appreciate hearing from y'all what you'd do in my shoes.

Oh and I forgot to mention that I'm not scared of a larger array either just as long as I'm not way, way overkilling things for no reason at all.
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Old 08-03-2012, 01:19 PM   #3  
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Welcome to the forum tbone937! Excellent first post!

Given your tvfool report, you have a decent shot at a successful attic install. Of we won't know for sure until you try it, but projected signal strengths are sufficiently high that I would consider an attic install. I personally use a DIY M-4 antenna in my attic and I suggest you use the same. The M-4 has been extensively modeled and field tested in the US and Canada. It is available as a kit or can be built from scratch (what I did), see: http://m4antenna.eastmasonvilleweather.com/

I suggest you build or buy the kit with 9-1/2 inch long whiskers and 9 inch bay spacing. Drawings are shown here: http://m4antenna.eastmasonvilleweath...0Drawings.html

Mclapp includes all the needed hardware for assembling the kit (his portion). I've attached a picture of my traveling M-4 which has been in and out of my truck and several attics. It looked much more professional when brand new... :-) The M-2 has about 3 to 4 dB lower gain than the M-4. You can see the balun attachment in the two bay picture (m-2).

In your case, the important nearby stations are UHF and thus, you only need a 24 inch wide by 36 inch tall reflector. You will need to build a frame for the reflector and antenna. The attached picture shows one way of building this frame out of electrical conduit and PVC couplings. Electrical conduit is cheap (a 10 ft piece of 1/2" diameter electrical conduit sells for $1.50). You'll need two pieces of conduit. The 1/2 inch PVC couplings are 33 cents each. You'll need six 90 degree elbows, four t's and one crossover. I used spare fencing for my reflector. You can use a less expensive approach. Line one side of a 24" by 36" piece of cardboard with aluminum foil using two sided tape or simply taping the surplus on the back side. If you have a seam in the foil, the seam should run horizontal, not vertical. Attach the cardboard to the frame by using zip ties or screwing the cardboard to the corner elbows.

The elements of the antenna are mounted 4 to 5 inches in front of the reflector. So will need a 34 inch long piece of conduit to mount the M4 elements (M4 kit). Attach 90 degree elbows to this piece of PVC and then attach to the reflector frame. You'll need a t centered along the top and bottom rail for attaching the antenna elements and a small piece of pvc pipe to connect the two couplings (ie elbow and t on each end). The elements are mounted to carlon pvc straps for 1/2 inch conduit (5 straps for $1.44 at Home Depot, in electrical department)

I made a pvc frame to support the antenna in the attic. It is easier to just use a three foot long piece of 1 inch diameter pvc pipe. Attach it to the rafters using metal straps for 1 inch pvc pipe, making sure it is perpendicular to the ground. I attach my antenna to the pipe with appropriate sized u bolts.

Let me know if you have any questions or need further clarification.
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Old 08-03-2012, 02:17 PM   #4  
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Hey IDRick, thanks for the helpful and well reasoned reply.

It's good to hear I was close to the mark with what I was considering for the build. I was figuring something similar to what you're recommending but didn't know what to look for with regards to exact measurements and materials and the site you linked seemed to answer quite a few of those questions rather well.

Regarding the reflector, the instructions (and yourself) mention that foil would work just as well as wire. Since this is going to be an indoor install (and hence not exposed to the elements) would a suitably braced/backed reflector made of one layer of aluminum foil serve as well, better, or worse than the fence material I saw mentioned here and in other places? I can't help but wonder if someone has empirical evidence on this exact thing somewhere and if it's a matter of buying Al foil or buying a scrap of fencing, that's honestly a wash for me since i don't have a bit of either at the moment so I might as well make the intelligent purchase.

Also, the copper wire for the elements and phase line were listed as #10 and # 12 respectively. Is there anything noticeable to gain/lose from substituting materials or material sizes?

Maybe I missed it but what are the specs for the balun this design will need and is there? I didn't see a materials list right off the top but I figure I could throw one together and hopefully not need to make too many trips to the hardware store and back. Moveover, is a Balun a Balun a Balun or are there any gotchas I should watch out for regarding buying this part?

Seems like a rough version of the punchlist for materials would be:

Reflector Material/Structure
Copper for Phase wire and Element Whiskers (various sizes)
1x Balun
Coax (not sure where/how much needed or if tools required to put connectors on are mandatory)
Mounting hardware/PVC as needed
Solder?

That sound about right? Thanks again.
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Old 08-03-2012, 02:49 PM   #5  
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Great questions!

The computer modelers tell me the best forward gain is obtained with a solid reflector. The loss in forward gain is very slight when one moves from solid to a wire reflector with 1 inch of horizontal separation. Aluminium is the cheapest and I would use that if I was merely building and installing. I bought my larger reflector at a local farm store for $8 (1x2 wire fencing, 3ft by 3ft in size). My traveling M4 needed a stronger build to sustain the abuse of moving it around so frequently... The wire reflectors really add rigidity and strength to the frame when properly installed.

I use number 12 gauge wire. With Yagi antennas, the element lengths change with varying guage wire but the changes are very small between 10 and 12 gauge wire. No need to adjust dimensions with the 4 bay antenna.

There are no specific requirements for the balun. I like the Channel Master ones that I bought from Solid Signal (internet distributor) but you can probably do well with most any indoor baluns that you can find at a local big box store. Indoor baluns can be bought for about a dollar at "dollar stores" while hardware stores sell outdoor versions for 3 to 5 dollars each.

Good RG-6 coax is sold in set lengths with connector ends or in bulk rolls (100 ft, 500 ft, and higher). I used Carroll brand coax with tri-shield (~$20/100 ft at Home Depot). It is well worth the price to buy your own tools for adding compression connectors to coax. The process to install the connectors is very simple. I purchased a coax cable kit from Home Depot that included the cable cutter, compression tool, 10 compression connectors, and simple plastic case for about $30. You could buy the component separately off the rack for the same money. If you do, buy the 25 pack of compression connectors. Amazing how cheap it is to make your coax cables versus buying that length at the store! :-)

I soldered all the whiskers to the phase line. The antenna will work just as well if you don't solder, especially with an undisturbed attic install.

Your list of materials looks about right. I have a price list at home, I'll post it later today. Good luck!
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Old 08-04-2012, 11:18 AM   #6  
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I have attached the Bill of Materials for a DIY M4 antenna. Costs could be lowered in an attic install by using aluminum foil + cardboard for the reflector. Many probably have an indoor balun laying around for free so no need to buy a new one. May also have leftover copper wire from other projects. A well built M4 for and outdoors mount is going to cost about the same as a commercial 4 bay but the M4 have higher UHF gain and modest high VHF gain.
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Old 08-04-2012, 03:29 PM   #7  
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Red Green sez - if women don't find you handsome -
They should at least find you HANDY!

Probably not the best place to start - making your own television antenna.
But to each his own.

Hope it works out for you.
Next time ask for advice before you purchase and you will come out ahead.
Most antenna's that dont look like antenna's or cost much - usually don't do much - unless you can see the light blinking on the tower.

Putting the antenna in the attic is like putting a lamp under a bushel basket...
JMHO
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Old 08-04-2012, 05:58 PM   #8  
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Quote:
Originally Posted by JB Antennaman View Post
Probably not the best place to start - making your own television antenna. But to each his own.
Individual opinions will clearly differ. In my case, there were divergent views on which antenna to purchase and the need for a rotor. I was not interested at all if a rotor was required and was willing to consider an attic versus a roof install. Using well designed/proven DIY antenna enabled me to test whether I needed a rotor and where to mount the antenna. My first DIY cost less than $20, much cheaper than a commercial antenna. For me, it was a good idea and proved that I could successfully use an attic install and no rotor for a very small sum a money. IMO, it is a great idea for people to test at their preferred location. If it works, great! If not, then move on to Plan B.
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Old 08-04-2012, 07:14 PM   #9  
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I built a M4 using coat hangers and a 2x4 with no reflectors. My only cost was the balun. The UHF stations were at 100% with the antenna in my closet five feet above ground going through a brick wall! The towers are 18 miles away. The problem I had was there are a few VHF hi stations here, so I put up a Radio Shack antenna I already had for them. But I think the M4 is a good start.
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