G0AOZ
join:2004-08-15
U.K.
| reply to olanin1
Re: Make my own omni antenna from coper wire
The homebrew omni's certainly look interesting... As to whether or not they work as well as claimed, I've no idea. However, the basic principle looks ok.
I would add that accuracy in cutting and shaping the wire is very important at these frequencies, with a few millimetres out possibly resulting in poor performance. Not only does an antenna need to be resonant on the desired frequency, but it also needs to present the correct impedance to the transmitter.
I've just discovered that a commercially made 7dBi omni produces very erratic results with a WAP54G on the higher channels, but set to channel 1 the AP performed faultlessly. This tells me that either it has a very poor impedance match at the higher channels, or more likely the antenna is cut to resonate at the lower end of the 2.4GHz WiFi band. Possibly trimming a millimetre off the element might allow it to work on higher channels, but since it's now working ok I'm leaving well alone!
You would not double the dB gain of this antenna by doubling its length. Provided you carefully matched any additional sections above the original element, you could expect to gain a few extra dBs at best. However, although you would still maintain an omnidirectional radiation pattern, the more gain you squeezed out of it, the flatter would be the signal. In other words, you would lose signal radiation above and below the plane of the antenna, at the expense of concentrating it outwards at 90 degrees to the vertical.
ROGER. |
