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In ,
(Antennahead1) wrote: I am thinking about getting a 5/8 wave antenna, most likely the Imax 2000. Does the GPK for it wrap around so that it is centered? I can't tell from the drawings I have seen posted. If I can get only a bracket or make one myself, would the performance be better with longer radials like Francis 8' antennas or something similar? I don't know about those specific antennas. I do know that the A99 may or may not work better with the ground plane kit (mine didn't). How does the angle affect gain? Lower radiation angle improves gain at ground level. A Shakespeare Bigstick is a vertical coaxial antenna, and it's radiation angle is parallel with the horizon (ideally). A 5/8 wave antenna will radiate up at a shallow angle, but the lobe is 'longer' than a half-wave dipole (again, ideally). People using both have different reports. So it's really a coin-toss. I an interested in reducing TVI, You should get your radio tuned up by a legitimate CB shop or ham (not one of those 'golden screwdriver' techs), and add a low-pass filter. improving groundwave performance Groundwaves at 27MHz are limited mainly by the terrain. If you are in a hilly area or have lots of buildings, there's not much you can do. If the area is relatively flat, just mount the antenna as high as possible. But the latter follows the law of diminishing returns at about 20 to 30 ft. and reducing skip as much as possible. There's not much you can do about that either, except to stay away from the toiletbowl (Channel 6), or use a beam antenna. What is the difference if the radials are horizontal vs 45 degrees or some point in between? The angle of the ground radials changes the input impedance of the antenna. For a 1/4 wave vertical, if the ground radials are mounted 45 degrees down, the input impedance is about 50 ohms, which matches the radio and coax quite nicely. BTW, that applies for full-length ground radials. I have doubts that those short little nubs Solarcon claims are ground-plane radials will behave the same. Actually, I think they are intended to keep RF off the coax, but who knows.... Does the bracket need to be below the matching circuit rings or is there another position that would be better? I am using a 37' pole and it is well grounded with three 8' rods and another dedicated rod through the basement floor that attaches to my radio. TVI has not been a big problem with my A99 but I would like to improve ground wave performance. With my current setup, I typically tx/rx out to 40 or 50 miles. Is that good/typical for an omni type antenna? Very good, and much better than typical (assuming you are running legal power). So well, in fact, you should consider the old proverb, "if it ain't broke, don't fix it". How much farther can I expect to reach with a 5/8 wave? Beats me. People have claimed different results. I don't think you will gain a whole lot, if any, and definately not as much as a beam antenna. You can make some BIG gains with a beam. Has anyone ever removed the flat mounting plate on the Imax 2000 so the A99 radial kit can be used? I dunno. http://groups.yahoo.com/group/11meteramps/ It's nice to see someone paying more attention to antennas, since they can provide amplifier-like gains for Tx -and- Rx without the splatter-box. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#3
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get a beam antenna
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#4
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The "Mastadon" never came to market. Its the INTERCEPTOPR 10K!
http://www.a1antennas.com/ Several sing the praise of the beefed up version by Jay-in-the-Mojave he calls a Mastadon. Assuming you'll be on eleven meter, concerning the skip, it's fading until next cycle when it will return again. When it's running hard, all you can do is change the freq or get a directional. |
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