DIY HDTV Antenna

[erwin1978]

I just got bit by the antenna bug. There's got to be some knowledgeable people here so I thought I would start a discussion about antenna design.

I've been looking to improve my reception for OTA HDTV. My amplified bunny ears just isn't good enough. I'm about 35 miles away from the big antennas with line of sight but my reception is weak on a lot of channels. I did some research and came upon the Antennas Direct DB4 antenna and the horde of hobbyists that have copied the design using coat hangers. It looks cool and a lot of people seem happy with the performance. Have any of you built this antenna with success? I'm looking to make one myself.

 

[Deathhorse]

http://www.antennaweb.org/

take a look here maybe it will help i get a couple channels with a super crap free design off the web

 

[Paperdoc]

First issue you'll have to check out is this: most of the newer HDTV OTA channels are on the UHF band, but some are not - they just re-used frequencies in the VHF band. That makes antenna design a bit tricky, because the two old VHF bands covered roughly 55 to 215 MHz, whereas the UHF band goes from 470 to about 800 MHz. So you need to know the actual frequency, or at least the broadcast band, of the HDTV channels you are trying to tune into. The TV stations certainly will tell you that info.

Now to the antenna design - there are MANY. One that has garnered a lot of attention from DIY people is called the Gray-Hoverman antenna. There are several variations on it since it was first proposed about 60 years ago by its creator. Current design variants include near-fringe and deep-fringe signal areas, wide-band and narrow-band versions, etc. Search on the web for Hoverman or Gray-Hoverman antennas, and you'll find lots to sort through. Most have extensive details of design, construction tips, performance measurements, and how to use the design principles to customize it to your specific needs.

You are right to look at better antenna designs. Retailers often try to suggest that a bigger more powerful amplifier on your old set of rabbit ears is all you need, and that's rubbish! First you need to grab the best possible signal from the air with the best antenna design. That gets you the highest signal-to-noise ratio, and then you can amplify from there.

 

[coolmeadow]

I built one from these plans a little over a year ago. http://www.mikestechblog.com/joomla/misc/hdtv-antenna/127-build-high-gain-hdtv-antenna-plans.html Great reception!!! I used aluminum square, angle and flat pieces for the structure, and mounted some modified cinch plates to hold the 'feelers' and insulate them from the aluminum. Feelers are made out of 8 guage copper wire. Soldered all connections. In the Dallas/Fort worth area, I'm on the far west side past Fort Worth, I get about 35 or so channels, all crystal clear 780 and 1080. Use this site to find where to aim the antenna. http://www.tvfool.com/index.php?option=com_wrapper&Itemid=29 If you can rotate the antenna, you can change for best reception if transmitters are located in different areas. I'm a good 40 miles away from transmitter hill that serves the DFW area.

Guess we can't store pictures here like my wood forums to show pictures, and I don't have these online to link to. Hope this helps! Jim.

 

[lakedude]

1) http://tvfool.com/ +1

2) Notice how channels are virtualized. The very first time you look for a signal (either manually or with auto scan) you find the station by the actual broadcast channel number. Subsequently the channel is located by the virtual channel which might be the station's old channel number before digital came on line.

For example in our area channel 51 is actually broadcast on channel 50. On a new TV you must type in "50" to find this channel the first time (or do an auto scan). Once the TV station "lies" to your TV set the station is remembered as channel 51.

The reason this is important is if you have your antenna pointed in such a way that a station is not picked up by auto scan you will never find it even after repositioning your antenna unless you either run auto scan again or use the actual broadcast channel number. Once a channel is learned you use the virtual channel number...Confused yet?

3) The size, directional heading, height and location of an antenna are the most important factors, amplifiers not so much. Garbage in, garbage out and all that rot.

 

[silverpig]

I made a coat hanger antenna out of some coat hangers (of course), a piece of 1x4, a few screws, and some wire. It worked pretty well, but I wasn't in a great location for reception so I didn't get much.

 

[erwin1978]

One instruction I read recommend using 14 awg or thicker wires for the phase line and yet the balun have 23 awg wires. Wouldn't it be beneficial for the baluns to use the same thick wires? I was thinking I can make the balun as or is the benefit miniscule?

 

[lakedude]

The size of the wire has very little to do with electrical properties in this application. The reason for thicker wire is for physical strength. The elements are just single wires so they must be thicker so they hold their shape. The reflector is a web or mesh which is stronger so it can be made from thinner wire, same goes for the connecting wires. The current is tiny so the size of the conductors could be tiny as well.

BTW the dimensions and crossovers must be such that the elements add together constructively. It is possible to make a 4 element antenna in which each element adds together in a way to cancel each other out and actually be worse than just a single element antenna.

 

[samuraizero]

You can buy an antenna for ~30 dollars anymore. May not be worth it to do it yourself

 

[erwin1978]

Yah, not much to save money. I'm doing mine for the sake of doing it and perhaps learn something. I'm almost done.

 

[billbillw]

I've been an OTA user since about 2005. I will tell you, just about any antenna mounted outside will perform better than even the best design mounted indoors.

My area has mostly all UHF, plus two high VHF channels since the ATSC transistion.

I've been using the original Channel Master 8-Bay for years. It has been superb. Back when I bought it, it was only ~$45?
I've been getting 95% or better signal strength on all the station at 35 miles.

That 8-bay design is probably the best all around for modern ATSC reception if you have mostly UHF and only high VHF. To me, that original design would be pretty easy to replicate for a DIY. The tight mesh reflector behind is what helps with the VHF reception.

This is what the original CM-4228 looked like:

http://www.hdtvprimer.com/antennas/cm4228.html

 

[AD5MB]

bigger antenna element diameter = wider bandwidth. in simple terms, it works better for more adjacent channels.

if you are making an antenna with wire elements, thicker wire = thicker elements. so thicker wire is better. Copper pipe or aluminum tube is way better. which is why commercial TV antennas are made with aluminum tube.

 

[Dannar26]

So what would you reccomend to somebody in an apartment situation?

Are there any decent indoor solutions?

 

[Red Squirrel]

I was curious to see if they turned up any HD OTA signals here so I shoved a random piece of telco frame wire I had laying around the house into the antenna plug and BOOM I got Global in HD and it was crystal clear.

You don't really need anything too fancy for an antenna if you're in town. I guess it helps that I can see the tower from my front window. In fact when it rains I can see the reflection of the beacon on my driveway lol.

I'd say start with a simple wire, and if the signal is not good enough then experiment from there.

 

[piasabird]

I purchased a HD Antenna and I can get in about 5-10 channels of varying quality. Sometimes we use it to watch the weather and a couple local channels if there is a weather event. I don't have cable TV because I dropped the service. I do have Internet and watch a shows on various websites.

I think you need a diff antenna to puck up UHF or whatever.

Mine is an indoor/outdoor antenna.

 

[NoCreativity]

Yah, not much to save money. I'm doing mine for the sake of doing it and perhaps learn something. I'm almost done.

What design did you end up going with? How well does it work?

I went with a channel master 2018 mounted in my attic. Gets great reception from 15-30 miles SW of my house and even catches a channel located about 30 miles SE (about 90 degrees away from primary antenna direction). Seems to work well during inclement weather too. It's a big beast though and you need a good amount of space for mounting. Would like to have built my own but I just didn't have the time.

 

[erwin1978]

I copied the design of the Antennas Direct DB4. It's a very well documented design so it was an easy choice. I was originally just going to use coat hangers for the elements but I found 9 gauge utility wire at Home Depot and I went with that. Fifty feet of it for $11. I used PVC pipes for the frame and some acrylic blocks to attach the elements to. The phase lines are 14 gauge copper wires. The design employed 9.5" elements.

I put the antenna in the roof space of the garage. Despite a ton of electric wires running in from the outside and metal truss braces I had strong reception on three televisions connected to the antenna. I'm not even using an amplifier. I receive all channels I'm supposed to get and the towers are 30 miles from me with line of sight. I intend to add a reflector but I may not need to given what I see. I haven't tested how it does when it's raining since I live in the desert.

 

[Paperdoc]

Very nicely done! And thanks for showing us.

I, too, mounted my antenna in my attic. It was a lot easier than attaching to the roof. It was also easy to run an electrical cable up there and install an outlet so I could plug in the broadband signal amp I put right at the antenna before sending it down the coax to the basement and my distribution system. Didn't built the antenna, just bought a good poor-signal VHF / UHF antenna because, at the time, local stations were still on VHF but planning the change to Digital broadcasting on UHF. That showed me something really interesting. The VHF signals were not too bad (one noticeably weaker than others), but the digital signals are always crystal clear. With digital, you get near perfection or nothing - no in-between junk!

 

[erwin1978]

Does anyone know what the purpose of the twist in the phase line?

 

[erwin1978]

I found this impedance calculator for proper phase line separation: Z= 276 Log (D/r). D is the distance between the centerline of each wire and r is the radius of the wire. The antenna I made called for a 1.25" phase line spacing but based on the equation that equates to around 400 Ohms impedance with a 14 awg wire. I thought the antenna is supposed to be 300 Ohms?