On Fri, Aug 13, 2004 at 12:22:05PM -0600, Howard Mark wrote: | This is technically not true. The antenna length should be a binary fraction of the wavelength.
Yes and no ... not all binary fractions are ok. Nothing smaller than 1/4 wavelength is resonant without some sort of matching setup (probably a loading coil), and resonant antennas are much better than non-resonant ones. | For example a good 1/4 wave antenna is not as effective as a good | 1/2 wave. HOWEVER a well tuned 1/4 wave antenna beats a poorly tuned | 1/2 wave any time. True. | The usual antenna length for 72mhz is about a meter. You can use 1/2 | meter pretty effectively. Not so effectively. 1/2 meter is about 1/8 wavelength at 72 mhz. It won't be resonant, not even close. Not even if you've got two of them in a full dipole. I don't know how much worse than the stock antenna it'll be, but a factor of 6 power loss would not surprise me. A loading coil could be used to make an 1/8 wavelength antenna resonant, but it still wouldn't be as good as a full 1/4 wavelength antenna. | You can make a simple effective dipole just like you want as follows. | Put half the antenna in one wing (1/2 meter) | Put a ground wire in the other wing (1/2 meter) Sorry Mark, but that's wrong. You'd want a full meter on both sides. A full dipole is 1/2 wavelength total, but at 72 mhz one meter is only 1/4 wavelength. Doing what you're suggesting would be much worse than the stock antenna. Also, you'd need to open up your receiver and find where the other RF input lead is and connect the rest of your dipole to it. It's probably not worth the trouble for most people. | Here's a link that may help: | http://www.angelfire.com/mb/amandx/dipole.html Yes, that's a nice page. But if you enter in 72 mhz, it's little calculator tells you that your entire dipole will be 6.5 feet -- not the meter that you mentioned. -- Doug McLaren, [EMAIL PROTECTED], AD5RH "When I was your age, television was called books." RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off.
