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January 9th 05, 03:44 PM
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Howard wrote: On 8 Jan 2005 18:19:19 -0800, wrote: How would you go about tuning a ground plane antenna? Is a ground plane a good antenna for 2 meters/440? On another note, I have read about discone's being very broad banded. Are these the best antenna for scanner listening? A 1/4 wave ground plane is tuned by varying the length of the radiating element. Calculate the length, add a bit for good measure, build it then tune it by pruning the length (in small increments). The tuning can be done using an SWR analyzer or as most of us do, with a radio and an SWR meter. Discone's do offer broadband coverage, though I don't have direct experience to say they actually work well, great or poorly. I do know that for my scanner I use a 1/4 wave ground plane that was built for 220 MHz and it works fine - for a reference point though I am in an urban area and most of what I listen to is within a 15 mile radius. In order to decide what's best you should first establish your purpose; are you in a fringe area, do you need directional coverage, do you scan a wide range of frequencies or are your listening interests all in the same "neck of the RF spectrum"? Do 1/4 wave ground planes work well for 2 meters? (Send and receive). Would they work as well as a j pole? What if you use different size elements? I just did not know what a discone would do for 2 meter send and recieve compared to a ground plane. On the scanner, I live in a fringe area for police but can pick up the police on a homemade wire 1/4 wave for 450 mhz about 20 miles away. What eventually I would like to do is pick up air traffic. And also pick up various other frequencies like ambulance, state police, etc. or your scanner do you use one antenna or several? |
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