Modern broadband TV antenna designs use computers to vary the element
lengths and spacings in order to search through a large number of "de-tuned"
antenna designs until they stumble across a "good enough" design that
more or less optimizes gain across the entire design bandwidth:http://ic.arc.nasa.gov/people/jlohn/Papers/ices2001.pdf
Hence, it would be difficult for you to build a multi-channel Yagi antenna.
The above recommendations are very good for $20-50....
But, if you just must DIY, Single Channel Yagi info is found here:http://www.skyscan.ca/Antennas.htmhttp://www.ifwtech.co.uk/g3sek/diy-yagi/http://www.k7mem.150m.xxx/Electronic.../yagi_vhf.html
[For some reason forum won't accept this webite. Replace "xxx" with "com"]
Note that Ham Radio boom designs are matched to 50-ohm transmitters....close enough???
However, in the VHF band, the bandwidth in a moderate to high gain Single Channel
Yagi may not even cover CH11, and the severe slope in frequency response
through CH10 and CH12 could cause problems:http://www.cebik.com/vhf/scales.html
An LPDA (Log Periodic Dipole Array) would be a more feasible multi-channel DIY project.
It provides more or less constant gain across all channels, at the expense
of maximum gain on a single channel.
DIY LPDA info is found here:http://www.wb0dgf.com/http://www.physics.adelaide.edu.au/~...g-Periodic.pdfhttp://www.qrz.com/download/antennas/index.html
The lowest and highest design frequencies for the LPDA should be about 20 percent
lower and higher than the desired reception frequencies.
See LPDA Spread Sheet Calculator below (from QRZ) for an example Hi-VHF Band design.
LOGPERIO.zip 8.1064453125k . file