More on DIY UHF Antenna

July 29th, 2009

I’m surprised that my antenna project drew that much attentions. Okay my friends, the following contents are some more info/FAQ that I’ve been asked these days.

Is this an “HDTV antenna”? Yes, if you mean picking up HD signal via this antenna. I have no problem receiving all OTA (over-the-air) HD signals.

You sure this works? Yes of course. The “four diamonds” antenna is actually a Doppler rectangular ring antenna, and there were commercial products based on similar designs. I use “were” because I can’t find it in the US but I saw pictures of old RadioShack antenna designs based on Doppler ring.

How do I hide the antenna? Well, there are many ways, and I’ve purchased a wood poster frame (12″x40″) from Joann’s which perfectly covered the cardboard hosting the antenna. You can use tricks similar to this and camouflage the antenna. Use frames of wood, glass or plexiglass only, no metal frames please.

How good this antenna is? The reference design should get you peak gain of 12 db (without reflector) to 15 dB (with reflector). Please note this is not a verified number, and I’d appreciate if someone can help with the exact NEC-2 plot. FYI, the bow-tie antenna typically has a peak gain of 11dB (DB-2 with reflector) or 13.5 dB (DB-4 with reflector, the coat-hanger bow-tie on YouTube is this type). Gray-Hoverman original design promise peak gain of 15dB (single-bay) and 17dB (double-bay). Peak gain is not accurate but should give you some idea about how good this little thing is.

Why this antenna? There’s already one on YouTube (coat-hanger bow-tie) and super-antenna (Gray-Hoverman). Well, I’m very certain that this is the easiest DIY antenna: you need only wire, cardboard, pen, ruler, pliers, and tapes, and you’ll get a high gain antenna (better than many antennas in store). No drills, no saws, no screws, no PVC pipes, no dust and can be worked on a dining table (that’s where I did mine).

Can I use coat hanger wires? Yes of course, if the coat hanger wire is longer than 7 ft, go for it.

Can I use it with pre-amps? Yes, you can use pre-amplifier with this antenna, but there’s a trick. The cable connecting the antenna to the pre-amp must be very short. I use the Winegard AP-8275 with my antenna and get marginal improvement of signal provided that the cable is shorter than 3 ft. So, it depends, you might not need a pre-amp at all. The good thing of digital TV is that you don’t need to worry about over-amplification most of the time. Modern digital TV receiver is not very sensitive to over-amplification. However, this is not the case for my Toshiba REGZA. Therefore, just tune down the signal gain if your TV behaves weird.

What about connecting this along with my cable? Well, this is a good question, and unfortunately the answer is that it depends. Some cable companies’ set-top box has outputs like DVI or HDMI, and it’s not an issue at all. Others might still use the antenna input, and you’d better checkout BestBuy or RadioShack to get things like a switcher or splitter. Again, this depends on the TV model you have, so make sure you write down the TV model and ask your technicians about what you shall get.

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