Yes element length is very important. Here is a link to a simple chart. TV Rabbit Ear
Keep in mind the channel number referenced are for real channels, not the virtual channel numbers displayed on the TV which often times have no relevance to the frequency the signal is being transmitted on. It's not difficult to find online half wave length calculators for dipole lengths. The basic formulas are quite simple. Keep in mind bow tie type antennas are of a broad band design and are closer to one wave length wide. There are many other factors that come into play in antenna design, and computer programs like 4nec2 that can be used to design better antennas.
I reread your previous thread. http://www.dtvusaforum.com/dtv-hdtv...ssion/73299-greetings-san-antonio-puzzle.html
If the antenna you are thinking about modifying is the Winegard FV-HD30.
There is no practical way that I know of to modify a FV-30BB antenna to receive channel 2.x. KCWX is listed as having applied for channel 8 in your area if they actually have that one on the air it should not be a problem to receive. If the signal is only available on real channel 5 then you will need an antenna built to receive low VHF and possibly need to do some work to suppress house hold RFI which can be a real problem on low VHF.
I feel a bit like I'm merging three threads by commenting on the Winegard FV-HD30. While I could be wrong what the antenna looks like to me is a UHF hour glass loop with added elements to lower the SWR on high VHF, and carefully placed, and sized reflector element that give it some forward gain on UHF, and a bi-directional pattern on high VHF. Look at post #20 in this thread. http://www.dtvusaforum.com/dtv-hdtv...cussion/16920-freevision-fv-hd30-antenna.html
I can provide more information on hour glass loop antennas. Anything I've tried to improve the VHF response of an UHF Hourglass loop antenna as severely distorted the UHF reception pattern of the antenna. I admire what Winegard has done. A very compromised little high VHF/UHF antenna in a small package that will work great in good signal areas.
There are two towers with the same name, KCWX, one at 352 degree and 56 miles away. The other is 91 degree and 8 miles away. My antenna is pointed East (90 degree) so that means my antenna are not capable of receiving VHF LO.
I can't post the link to this one because it shows my address.