Don Cross built his own HDTV antenna (and you can too!)

See also: Make your own 3G or 4G antenna, by Damon Chandler.

1 June 2009

I finally caved in and purchased an HDTV, since we are days away from the demise of analog television. There is no cable TV available where I live, and I did not feel like spending $50 per month on satellite service, since I really don't want to spend that much time watching TV in the first place. Without an antenna attached, the new TV didn't pick up anything at all, of course. I tried hanging a 4-foot section of insulated wire from my window and poking it right into the coaxial receptacle on the back of the TV, and sure enough, I could receive most of the stations in my area just fine. But there were quite a few that were hopelessly garbled. I experimented with even longer pieces of wire, but this made things even worse.

I did some research and I found the following do-it-yourself HDTV antenna design:

TV Antenna Plans — schematics and instructions by Peter A. Daly.

Below is a photo of me holding the one I built for myself. It works great! Just about every TV station in a 25-mile radius is coming in crystal clear without any distortion that I can notice.

Don Cross holding his home-made HDTV antenna.
(Click for larger view.)

Here are some notes of things I figured out or read elsewhere:

12 June 2009

The other night I moved the antenna into the upstairs side attic above the TV. I drilled a hole through the attic floor to feed the cable through. I have a 16-foot cable connecting the TV and the antenna, and there is a fair amount of cable slack, so the antenna is probably about 10 feet above the TV now.

Before and after I raised the antenna higher, I went through all the channels and wrote down signal strengths, based on the TV's built-in signal strength meter. Almost all of the TV signals are stronger now. The signal strength meter has a scale that goes from 0 to 100, and on many of the channels the strength went up by 20 points. None of the signals got weaker. I can even receive 3 channels now that I couldn't before! I like the fact that the antenna is so much higher, but is still sheltered from rain and lightning.

Using the wonderful TV Fool web site, I can tell that just about every TV station I care about is to the south of my house, so I am thinking I might be able to improve reception strength and reduce multipath interference (especially during bad weather) by adding reflectors on the north side of the antenna. This weekend I intend to experiment with some simple reflectors made of cardboard and aluminum foil to see if they make any difference, for better or for worse.

And while I'm at it, I may also experiment with making an entire antenna out of cardboard and aluminum foil. I think that would be pretty darn funny, having a high-tech piece of equipment attached to some cheap junk, especially if it worked well!

14 June 2009

Yesterday I tried two different experiments, neither of which provided any detectable change in signal quality.

First, I added two extra screws at the very center of the antenna for attaching the balun, as specified in the TV Antenna Plans site. Although I could not measure any difference in signal strength, I do have to admit that this antenna would have been easier to assemble if I had made it this way in the first place. My original approach made it awkward to hold two pieces of coat hanger wire, a washer, and the balun terminal in place while torquing down these two screws. For that reason alone, I recommend using the extra two screws and washers if you are building one of these antennas for yourself. Here is what the antenna looks like now:

Antenna with centered balun, hanging in attic.
(Click for larger view.)
Antenna hanging in attic, with balun centered.

The next thing I tried was to put a reflector on the north side of the antenna, since all of the TV stations I care about are to the south of my home. I used a cardboard box measuring 23"×23"×3.5", on which I taped two sections of aluminum foil measuring 9"×15". This did not make any detectable improvement in signal strength either. I don't know whether aluminum foil isn't a good enough reflector of UHF, or 3.5" is too far away from the plane of the antenna, or something else is going on. The photograph below shows the cardboard box after I ripped the aluminum foil off.

Cardboard box I used for the aluminum foil reflector experiment.
(Click for larger view.)
Cardboard box I used for the aluminum foil reflector experiment. The black rectangles show where I had the 9"×15" sections of foil.