Reflectors

What reflector to use and when ? A reflector can add considerable gain to the 4 bay antenna many times adding as much as 4db of gain. Reflectors can also cut unwanted signals from entering from the side or rear of the antenna. If you need reception mainly from one direction or need maximum gain a reflector is needed.
The reflector helps add gain mainly for 2 reasons
(1) The reflector reflects the TV signal back to the antenna elements which reinforces the signal already being received.
(2) The reflector generally improves the impedance of the antenna which creates a better match to the 300 ohm balun or feed line which increases energy transfer.

Without a reflector these antennas will give a bi-directional reception pattern with even reception each way and considerably less off of the sides. This is great for someone between 2 TV markets with fairly strong signals reliable UHF reception can be in the 30-50 mile range for a 4 bay depending on antenna placement, surroundings and terrain.
The curved or angled oversize reflector along with swept forward whisker elements can help narrow the beam width of the antenna by  squeezing the gain more in the forward direction and less on the sides and rear. This reflector also works well to enhance VHF-hi channel 7-13 reception. With this style reflector on a 4 bay UHF reception in the 60-80 mile range can be normal depending on antenna placement, surroundings and terrain.

Reflectors less than 34" wide don't work well for all the VHF-hi channels 7-13 but work fine for UHF. The narrower reflectors won't get as much advantage of the curve or angle and the narrowing effects of the forward beam but still give a good boost.
Reflector Materials
About anything metal will make a reflector in general larger diameter tubing or strips of flat stock can be spaced further apart and still achieve good rear rejection as compared to wire. Even good old aluminum / Tin foil strips running horizontally on a piece of cardboard will do the trick.
The key to a good reflector is the spacing between the horizontal running elements within the reflector and to make it the right width for the desired channels.

The vertical spacing of the elements has more to do with rejection of unwanted signals then gain. Good gain can be achieved on UHF with elements spaced as far as 4" apart and 2" is the point where forward gain isn't enhanced much if any. Rear rejection will still get better down to about 1" spacing but after that not much is gained. Wire fence makes an excellent reflector material 2" x 4" wire fence is a good choice for both rejection, forward gain, and wind loading. 1" x 2" fencing is even better for rear rejection on the upper UHF channels but does little for VHF-hi. Hardware cloth can make a good reflector but needs more support to keep it in place and if used outdoors the wind loading becomes an issue. I've used both tubing and wire fence with good results
Many times wire fence scraps can be found from a left over fencing job and old VHF antennas make a great source of tubing for reflectors

I now have a reflector mounting Kit available which makes mounting the reflector and the whole antenna much easier