TV Antenna Designs         back to S. Cain web page

        channel number confusion         Channel 10 design

UHF TV Log Periodic Antenna
    Materials 
Qty  Size  Length
  -   rosin core 60/40 solder
 5 ft  12AWG solid copper uninsulated wire (ROMEX house wire)
  4   terminal lugs
  1   75 ohm to 300 ohm UHF balun
  4   small wood screws #8 x .5" length
 1x6 or 1x8 wood plank about 16 inches long


This is a UHF only TV antenna (470-806 MHz) and not an all channel antenna. A separate VHF antenna is needed to receive VHF channels(174-216 MHz). In the Atlanta area I use 2 antennas connected together to receive all channels. My 2 antenna system is more complex than a single all channel but I do get an extra station. Some of my channels are weak and come from different directions. I hauled a small TV temporarily in my attic and hooked it up to my UHF antenna. I set the TV to a marginal UHF station, channel 14. Because of the UHF antenna's relatively small size, I was able search many locations in my attic and found a "good spot" that could receive this weak station. The VHF antenna would be very difficult to place in this location. Next I combined my UHF and VHF antennas with an inexpensive VHF/UHF combiner. The VHF antenna was already located in a "good spot" for the VHF channels 8 & 11. With two antennas I was able to set up for 2 "good spots" instead of one.

You build this antenna by constructing 2 quantity "Element Feed Arrays" and then screw them on a piece of wood. The illustrations show the two EFAs as red and green. They are made with 12AWG solid copper wire. The angle on the plank is not critical. It is important to have the 2 EFAs oriented in opposite directions as illustrated (the red E6 has to point the opposite way than the green E6). The antenna is based on design theory for log periodic arrays.

Construction Details



470-806 MHz, 12 in.
element
length in.
E
spacing in.
S
11.950
22.461.39
33.113.14
43.935.35
54.978.14
66.2811.7
470-806 MHz, 15 in.
element
length in.
E
spacing in.
S
12.020
22.441.45
32.953.21
43.565.33
54.307.89
65.2010.98
76.2814.71


 
Channel number confusion         top of page         back to S. Cain web page
There is some confusion about channel numbers. In Atlanta channel 11 (WXIA) is only a "virtual" channel 11. It is actually being broadcast on channel 10 (192-198 MHz). This puzzled me for awhile but I came up with the following theory.

Way back before digital broadcasting started there was no confusion - Channel 11 was broadcasting on channel 11 (198-204 MHz) with an analog signal. A few months before the June 2009 end of analog broadcasts, channel 11 started simultaneously broadcasting analog and digital. They kept broadcasting their analog signal on channel 11 but started transmitting their digital signal on a different channel. I guess they used channel 10 for their digital broadcast.

 
Channel 10 Yagi Antenna         top of page         back to S. Cain web page
Yagi type antennas feature high gain over a narrow frequency range. The design formulas only use the center frequency and there is no allowance for bandwidth with the equations I use. Yagi antennas do have some bandwidth - I just don't know how much. I have built a few Yagi antennas for UHF TV channels and they seemed to work well. Below is my design for the weakest VHF channel in the Atlanta area, channel 11. Atlanta has two VHF channels, 8 & 11. I am hoping that the channel 11 antenna will also pick up the stronger signal on channel 8.


Figure 3 Yagi antenna 3D view

You build this antenna by mounting elements to a boom. Refer to Figure 4 for element definitions. All elements except one are simply straight metal rods or metal tubes that are center mounted to a boom support. The one exception is the folded dipole. This element is bent at the ends and routed back to the center where the balun is connected.


Figure 4 Yagi antenna construction details

Yagi Antenna Ch 10
196 MHZ   64 inch   0.2 in dia rod
element length in. spacing in.
reflector 29.2 0
dipole 27.5 11.7
director 1 26.0 16.4
director 2 26.0 21.6
director 3 26.0 26.9
director 4 26.0 38.6
director 5 26.0 61.3