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#1
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Telamon wrote:
In article , Telamon wrote: In article , Dave wrote: John Smith wrote: However, in side-by-side comparisons on 10-6-2m antennas I have built, comparing a 5/8 against the 1/2 (construction methods/materials and matching components identical) ... the actual difference, in the real world, must be less than the width of a meter needle in the readings ... or, put simply, I no longer deal with the extra length required of the 5/8 ... your mileage may vary ... The advantage of a physical height (antenna length) between 180 and 215 degrees (see previous post regarding the magic number being around 195 degrees) is improved take-off angle and reduced skywave-groundwave interaction, not dramatic nearfield voltage increases. Regarding Mr. Smith's comments above my experience and others is the opposite. 5/8 is a much better performing antenna than a 1/2 wave for local VHF and UHF communications. Well worth the effort to build a 5/8 wave antenna over a 1/2 wave. The 5/8 had some kind of series load coil part way up the whip where the 1/2 wave match/compensation was done at the base so the whip was solid. Sorry I can't more specific then that as those experiments were many years ago. Mr. Smith is still lost in space. Here is an example of the 5/8 wavelength antenna I recall using in the center of the page. The one I used was permanent mount not magnetic though. The van roof it was installed on was the ground plane. http://www.new-tronics.com/main/html/mobile_vhf.html When this antenna was changed for a 1/2 wave a lot of coverage was lost. This was before cell phones so I had to start using pay phones a lot. The one with the center coil is a collinear. It is 2 stacked verticals with a "delay" between. |
#2
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Dave wrote:
... http://www.new-tronics.com/main/html/mobile_vhf.html When this antenna was changed for a 1/2 wave a lot of coverage was lost. This was before cell phones so I had to start using pay phones a lot. The one with the center coil is a collinear. It is 2 stacked verticals with a "delay" between. If I remember correctly, from running comparisons thought antenna prediction softwares, 1.5db is about the most "gain" which can, theoretically, be had between a 1/2 and a 5/8; and, not even "all that gain" (i.e., max 1.5db) is gained in such a narrow point or swath of pattern so as to account for "a lot of coverage lost." And, rarely, if ever, is the theoretically reached, in my humble experience. Something is obviously wrong with that whole statement ... perhaps a "chit poor" 1/2 is being compared to a reasonable performing 5/8? Regards, JS |
#3
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In article ,
Dave wrote: Telamon wrote: In article , Telamon wrote: In article , Dave wrote: John Smith wrote: However, in side-by-side comparisons on 10-6-2m antennas I have built, comparing a 5/8 against the 1/2 (construction methods/materials and matching components identical) ... the actual difference, in the real world, must be less than the width of a meter needle in the readings ... or, put simply, I no longer deal with the extra length required of the 5/8 ... your mileage may vary ... The advantage of a physical height (antenna length) between 180 and 215 degrees (see previous post regarding the magic number being around 195 degrees) is improved take-off angle and reduced skywave-groundwave interaction, not dramatic nearfield voltage increases. Regarding Mr. Smith's comments above my experience and others is the opposite. 5/8 is a much better performing antenna than a 1/2 wave for local VHF and UHF communications. Well worth the effort to build a 5/8 wave antenna over a 1/2 wave. The 5/8 had some kind of series load coil part way up the whip where the 1/2 wave match/compensation was done at the base so the whip was solid. Sorry I can't more specific then that as those experiments were many years ago. Mr. Smith is still lost in space. Here is an example of the 5/8 wavelength antenna I recall using in the center of the page. The one I used was permanent mount not magnetic though. The van roof it was installed on was the ground plane. http://www.new-tronics.com/main/html/mobile_vhf.html When this antenna was changed for a 1/2 wave a lot of coverage was lost. This was before cell phones so I had to start using pay phones a lot. The one with the center coil is a collinear. It is 2 stacked verticals with a "delay" between. I don't think it works that way. The coil is just a way to shorten the total whip length. I haven't looked at the design but I would be surprised if what you posted was true. -- Telamon Ventura, California |
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