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#1
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"Tam/WB2TT" wrote in message ...
If the second reflector is actually doing anything, which I doubt, you should be using a non metallic mast, and not bringing the coax down between the reflectors. Tam/WB2TT Actually, if you believe the yagi optimizer program, the second reflector is indeed not doing TOO much, but it does affect the back shape of the pattern, and improves the impedance bit, and also increases the dBd of the outer edge of the pattern by tiny bit too. And i did simulate having the mast at 48 inches from the DE, which i was advised was the distance where the mast would have the least affect. Changing the mast length in the YO program does affect the pattern shape though, so i tried to make the mast a non-resonant length. At any rate, we could probably survive without the second reflector, you are most likely correct, but maybe for the next design. It first, i considered having the "T" section of PVC pipe move outwards at a 90 degree angle, and then attach another section of 2" PVC that would be sticking out, so that the coax would be totally perpendicular to all the elements. But, this would be a bit unwieldy. Slick |
#2
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Slick,
The only thing about making the 48 inch mast non resonant is what's on the other end of it? A ceramic insulator is not the same as a Radio Shack steel house bracket. Since it is behind the first reflector, probably doesn't matter in the real world. Tam/WB2TT "Dr. Slick" wrote in message om... "Tam/WB2TT" wrote in message ... If the second reflector is actually doing anything, which I doubt, you should be using a non metallic mast, and not bringing the coax down between the reflectors. Tam/WB2TT Actually, if you believe the yagi optimizer program, the second reflector is indeed not doing TOO much, but it does affect the back shape of the pattern, and improves the impedance bit, and also increases the dBd of the outer edge of the pattern by tiny bit too. And i did simulate having the mast at 48 inches from the DE, which i was advised was the distance where the mast would have the least affect. Changing the mast length in the YO program does affect the pattern shape though, so i tried to make the mast a non-resonant length. At any rate, we could probably survive without the second reflector, you are most likely correct, but maybe for the next design. It first, i considered having the "T" section of PVC pipe move outwards at a 90 degree angle, and then attach another section of 2" PVC that would be sticking out, so that the coax would be totally perpendicular to all the elements. But, this would be a bit unwieldy. Slick |
#3
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"Tam/WB2TT" wrote in message ...
Slick, The only thing about making the 48 inch mast non resonant is what's on the other end of it? A ceramic insulator is not the same as a Radio Shack steel house bracket. Since it is behind the first reflector, probably doesn't matter in the real world. Tam, The 48 inches refers to it's position relative to the DE, not it's actually length, which in the ideal case would be at a non-resonant length. The yagi optimizer program i have shows that the length does indeed affect the propagation pattern. I'm not certain how the user has the mast mounted, but it's somewhere around 7.5 feet or so in length. At any rate, he is getting out very well! Err...i won't say at what wattage, someone might faint out there! hahaha! Slick |
#4
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where is the center of radiation on this antenna ?
where will the strongest field strength be ? |
#5
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i found this antenna page ,
can i use a coil for the use od decoupling the signal? http://www.packetradio.com/images/6mdipole.gif |
#6
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g subs inscribed:
i found this antenna page , can i use a coil for the use od decoupling the signal? http://www.packetradio.com/images/6mdipole.gif Yes. However you should investigate other matching methods - Google for the "Ross Dipole". Also look at Gamma matches and Delta matches - both are viable solutions for unbalanced feeder connection to a balanced antenna (like a dipole). -- BIAS COMMS Everything gets easier with practice, except getting up in the morning! |
#8
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(g subs) wrote in message . com...
where is the center of radiation on this antenna ? where will the strongest field strength be ? Looking at: http://www.drslick.org/Temp1/yagiplot.jpg You will notice the lobe is greatest at the rear (180), and this is because of an interesting use of the yagi optimizer program, where we actually used two directors to act as reflectors. So the strongest field strength will be where you point the driven element (dipole), and the weakest ERP will be where the two reflectors are facing. Slick |
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