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July 26th 05, 03:21 AM
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Thanks all, appreciate the info.
Greg. Richard Harrison wrote: Greg wrote: "Anyone know the formula (if there is one) for working out the spacing of the elemrnts on a UHF TV antenna?" It`s a choice, not a formula, because of many tradeoffs. There are many types of TV antennas For a particular frequency, Kraus shows a Yagi on page 66 of his 3rd edition of "Antennas" which spaces the reflector 1/4-wave behind the driven element, and (4) directors are used ahead of the driven element. Each director is spaced at a distance of WL/pi from its neighbors. This gives 15% bandwidth, plenty for a single TV channel, even for Channel 2 at 50 MHz. The UHF TV channels extend from about 500 to 800 MHz. 633 MHz would would be the geometric mean frequency. 95 Mhz would be the antenna bandwidth at 633 MHz. The geometric mean of two numbers is the square root of their product There are many tradeoffs in TV antenna design. Look at some good book concerning the subject such as "TV and Other Receiving Antennas" by Arnold B. Bailey. Chapter 12 deals with "Practical Aspects of TV Receiving Antennas. Best regards, Richard Harrison, KB5WZI |
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