Sunday, July 22, 2012

The simplest HDTV Antenna

There are free OTA (Over-The-Air) digital HDTV signals broadcast from the CN Tower. What you need is a HD TV with an ATSC tuner and a simple indoor antenna to pick up the OTA broadcasting HD channels for free. 

You can goto to see the location map for pointing direction between your home and CN Tower. 

The available ATSC Digital TV broadcasts from CN Tower:

The UHF dipole antenna for OTA broadcasts reception:

Since the HDTV OTA signal reception result depends on many issues, such as the direction and distance of your local OTA broadcast station, your window facing direction, the HD TV set or digital ATSC tuner receiver you are using etc., this is not a good idea to invest money for an indoor antenna without knowing the result beforehand.  
The following antenna construction is very easy to implement, it will be very useful for doing evaluation of the local OTA signal reception at your location.

The simplest HDTV Antenna
We are going to use a piece of coaxial cable to make a simple and cost effective UHF dipole antenna to receive the free local OTA (over-the-air) digital HDTV signals.  No soldering is needed. 

Find a coaxial cable of more than two feet long with a RF connector in one end.
Carefully using a razor knife, cut off about 6 inches of the black outer sheathing, but be careful not to damage the inner cable shielding i.e. the copper braid underneath. And completely removed the outer sheathing.
The exposed cable core wire with the separated braid.
Put the cable through a bag clip.
Use the clip to hold the antenna.  Trim the antenna span dimension to about 8.4 inches.
Mount the antenna to a camera tripod.
Time to test the antenna performance.
Turn on the HDTV set and start the auto program function to search for digital channels. All nine channels were successfully found.
See the reception result of the CBLT-DT 5.1 - CBC channel.
The reception result of the CFTO 9.1 - CTV channel.
The reception result of the TVO 19.1 - TVO channel.
The reception result of the CBLFT-D 25.1 - CBC French channel.
The reception result of the CIII-HD 41.1 - Global HD channel.
Note: The CIII-SD 41.2 - Global SD also use the same physical channel for signal transmission.
The reception result of the CFMT 47.1 - OMNI 1 channel.
The reception result of the CITYTV 57.1 - City TV channel.
The reception result of the CJMT 69.1 - OMNI 2 channel.
The reception result of all nine channels are unbelievably good in both Signal Strength and quality (Errors and SNR).  

The Finished Version
After month of reliable performance of the testing antenna, it is now time to wrap things up to produce an antenna with it's own stand as a finished product.

The first thing to do is to make the antenna module.
Find a plastic tube of about 9" long, and cut a slot opening in the middle.  
Insert the antenna (the separated braid and core wires) into the plastic tube through the slot opening.  Use hot-melt glue to fill the slot and firmly fix the cable end with it.  
Use the antenna rod and a PVC reducing bushing  to form a antenna module.  
Make a notch in the PVC bushing for the antenna rod to fit in.
Put the antenna cable through the bushing.
Use hot melt glue to glue the bushing to the antenna rod.

Make a stand for the antenna  
The body of the stand is an aluminum angle (1/16" x 3/4" x 3') with a PVC tube on the top and a small particle board as base plate.  A 3/4" PVC tube of 3 1/2" long is installed on top of the aluminum angle using 2 screws.
A 4" x 4" base board. A short piece of aluminum angle is used as corner brace to mount the vertical aluminum angle to the base board.

Install the Antenna module to the stand

Put the antenna cable through the PVC tube.
The antenna rod can rotate freely on the PVC tube.  

The antenna's reception direction is changed about 90 degree.  
A balun is used to prevent feedline pickup. With it, signal reception will not be interfered even when people is moving around the antenna.  Our balun is a choke made by winding the coax through three ferrite toroidal core three times. 
The antenna design is simple and small in foot print.  
Front view of the antenna with stand.  
The final version is to add the amplify to the antenna in order to enhance the signal strength and reliability. A RCA 10dB 50-900MHz amplifier is used.
The finished antenna with choke balun and amplifier.  

It is time to go completely cable-free, adopting over-the-air HD broardcasts and online streaming services.  In fact, the OTA broadcasts programming is the best 1080i HD video quality you can get, which is much better than through the scrambled cable transmission.