On Mon, Mar 24, 2008 at 11:47:16AM -0500, aeajr wrote: | I believe the signal pattern on a 2.4 GHz system is the same as a 72 MHz | system. Max signal is from the sides of the antenna. There is much | less signal coming from the tip.
If two antennas have the same shape, and the wavelength to size ratios are the same, then two antennas will have the same radiation pattern even if on different bands. (i.e. double the wavelength, double the size of the antenna, same radiation pattern.) And in general, the 2.4 GHz TX antennas have the same shape (your basic monopole/unipole/quarter-wave antenna) as your basic 7.2 MHz antennas, so the radiation pattern should be the same. However, there is room for differences, as the rest of the radio affects the radiation pattern as well (even if it's not intentionally part of the antenna, it's still part of the antenna), and so does that guy holding it, and the ground certainly has an effect, and since the ratio of the wavelength to the sizes and locations of these things does vary, so will the radiation pattern. To be sure, you'd have to either take a specific TX and situation and model it, or actually measure it, but I imagine that what aeajr said is probably close enough. I'm still surprised that vendors aren't at least experimenting with using a dipole antenna like this -- ---| |--- ====== | TX | ====== because that would create a radiation pattern where the strongest part would be aimed right at your plane. And while it would also be aimed right at you, a small shield could prevent that and increase the useful signal aimed at your plane as well. And the gain is pretty mild -- you'd still have good range even if not pointed right at your plane. | Pointing your antenna at the plane is not recommended. It's not so bad. If you keep your antenna aimed at your plane, then that will have approximately the lowest signal aimed right at your plane, which will give you the earliest indication of any problems. If you have problems, do like you do at 72 MHz and turn the antenna at right angles to the plane and run towards it if that doesn't get control back. This is if you're far out -- if you're close, then you should not have problems, no matter what direction your antenna is pointed. -- Doug McLaren, [EMAIL PROTECTED] If your parents never had children, chances are you won't, either. --Dick Cavett 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. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
