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#11
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Will get to you on the measurements. Going to find out whether a 3/8 3
element quad will out perform a 1/2 2 element. |
#12
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Why don't they put a price tag out there on them thar thangs!
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#13
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Have you figured out how you are going to make your spreader bars, what
are you going to use for the boom, are you going to go horizontal or vertical with it, or a combination of same, how high is your tower, mast pole, are you mechanically challenged or are you one who can challenge mechanics, what rotor will you use on it? That be about all the questions for you at this time. |
#14
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Steveo wrote:
Vinnie S. wrote: On 8 May 2005 17:34:14 -0700, "farmerjoe1" wrote: Late last summer we had a very close lightning hit,now my SWR's are high.Any way i can run some sort of test to see if the Antrton is shotred out? Nuke it and get the Imax 2000 or Maco. Vinnie S. Nuke all of those and get what I use for a ground plane. http://www.a1antennas.com/ Like this? http://www.a1antennas.com/order.html |
#15
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On 9 May 2005 17:47:14 -0700, "Cliff" wrote:
When compared to a stated db in a ground plane you should get at least 10db better with a 2 element quard. Go to: http://www.signalengineering.com/ultimate/ ***** I perused this page and for most of the info is adequate explaination. I think he really lacks good explanation is some areas. james |
#16
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Steveo wrote:
Vinnie S. wrote: On 8 May 2005 17:34:14 -0700, "farmerjoe1" wrote: Late last summer we had a very close lightning hit,now my SWR's are high.Any way i can run some sort of test to see if the Antrton is shotred out? Nuke it and get the Imax 2000 or Maco. Vinnie S. Nuke all of those and get what I use for a ground plane. http://www.a1antennas.com/ Like this? http://www.a1antennas.com/order.html STFU, asplundh boi. |
#18
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Just wondering where there is the 'lacking of good explanation' areas?
Shoot, I thought it was a fairly well done site! Much better than most of us can truly understand. I wished that when I built the first antenna I had had acess to that site. Would have kept a lot of 'trial and error' work from going on. james wrote: On 9 May 2005 17:47:14 -0700, "Cliff" wrote: When compared to a stated db in a ground plane you should get at least 10db better with a 2 element quard. Go to: http://www.signalengineering.com/ultimate/ ***** I perused this page and for most of the info is adequate explaination. I think he really lacks good explanation is some areas. james |
#19
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On 18 May 2005 00:52:28 -0700, "Cliff" wrote:
Just wondering where there is the 'lacking of good explanation' areas? Shoot, I thought it was a fairly well done site! Much better than most of us can truly understand. I wished that when I built the first antenna I had had acess to that site. Would have kept a lot of 'trial and error' work from going on. ***** Overall it is a very good site. It is by far better than many that I have seen in the past. But when some try to explain transmission line issues with a small working knowldge of them, the all to often too simple explanations or are lacking or misleading. In the explanation of why coax affects SWR. While it is not bad, it is typically and over symplistic. The real problem is that comon mode currents are often not understood as to how they are generated and what effects they have on SWR meters. Another thing is that the SWR bridges made for CB and many for Ham use are poor instruments to measure SWR. They are only good to about 3:1 and after that their accuracy suffers greatly. The best way to measure the SWR of the antenna is with a dual directional coupler. Preferably the power measurements should be a spectrum analzer. Also coax impeadance is determined by ratio of the inside diameter of the outer conductor to the outside diamter of the inner conductor and teh dielctric constant of the medium in between. Not just solely the ratio of the diameter. That would be true only of air dielectric coax. Coax loss is solely determined by the dielectric and not the shield. As long as the shield is in relatively good shape the sole called "leakage" loss is hardly measureable, even in relatively high power RF transmissions. A shield of 80% is still nearly 100% effective even at frequencies as low as 10 MHz. The openings in the shield would have to be at least 1/16 of a wavelength in order to start to be able to measure leakage. At 10M that is 1.25 meters. What causes dielectrtic breakdown is chlorine in the PVC, PolyvinalChloride, to leach into the dielectric and cause the characteristic impeadance to change. Also chlorine from sea spray that can leak into the coax from poorly assembled coax connectors. The site is right in that cox does need to be changed. Even the best installations require changing at least once every ten to fifteen yrs. One thing also about antenna design and installations. Unless you model the ground (Earth) for your area, you have missed a major influience on the performance of any antenna design or installation. There is a deal of hunt and peck to tame some designs. Especially dipoles that are not at least a wavelength above ground. Some designs behave better than others. james james wrote: On 9 May 2005 17:47:14 -0700, "Cliff" wrote: When compared to a stated db in a ground plane you should get at least 10db better with a 2 element quard. Go to: http://www.signalengineering.com/ultimate/ ***** I perused this page and for most of the info is adequate explaination. I think he really lacks good explanation is some areas. james |