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Post by Phantom309 on Jan 19, 2009 22:18:40 GMT -5
thanks for the feedback its alot of help! I have a 56 foot self support tower I was wondering now if I can mount my vertical antenna and beam on the same tower. If so how is the best way, will each still perform well? Will my match still be low? I hate small backyards!!!  |
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Post by spitfire441 on Jan 20, 2009 5:55:07 GMT -5
thanks for the feedback its alot of help! I have a 56 foot self support tower I was wondering now if I can mount my vertical antenna and beam on the same tower. If so how is the best way, will each still perform well? Will my match still be low? I hate small backyards!!! You CAN mount the vertical above the beam with no ill effects. I have done just that in many configureations over the years.  |
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Sandbagger
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Post by Sandbagger on Jan 20, 2009 8:28:32 GMT -5
thanks for the feedback its alot of help! I have a 56 foot self support tower I was wondering now if I can mount my vertical antenna and beam on the same tower. If so how is the best way, will each still perform well? Will my match still be low? I hate small backyards!!! You CAN mount the vertical above the beam with no ill effects. I have done just that in many configureations over the years. As long as the beams are horizontal....... Vertical beams won't work so well that way. |
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Post by spitfire441 on Jan 20, 2009 9:36:16 GMT -5
Granted, unless you space the omni vertical way above the beam. At least 1/4 wavelenth.
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Post by Phantom309 on Jan 20, 2009 18:49:47 GMT -5
I want to mount the beam vertical so they would need 9 feet or so between them and this wont affect the performance of each one. Thats good to know. Dont know what the height restrictions are where i live Im having a hard time to find out.
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Sandbagger
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Post by Sandbagger on Jan 20, 2009 22:25:04 GMT -5
I want to mount the beam vertical so they would need 9 feet or so between them and this wont affect the performance of each one. Thats good to know. Dont know what the height restrictions are where i live Im having a hard time to find out. If the mast (Unless it is not metallic) is allowed to extend through and above a vertical beam, the mast will act like another element (improperly sized and spaced) which will distort the beam's pattern and likely severely reduce your front:back ratio and/or forward gain. Any stacking that you do with vertical beams should be done with a horizontal boom. That way you will not distort the pattern. This is not a problem with horizontal beams as the mast would be 90 degrees out of the beam's polarity plane and would not affect it. |
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Post by BionicChicken on Jan 21, 2009 7:15:58 GMT -5
I want to mount the beam vertical so they would need 9 feet or so between them and this wont affect the performance of each one. Thats good to know. Dont know what the height restrictions are where i live Im having a hard time to find out. If the mast (Unless it is not metallic) is allowed to extend through and above a vertical beam, the mast will act like another element (improperly sized and spaced) which will distort the beam's pattern and likely severely reduce your front:back ratio and/or forward gain. Any stacking that you do with vertical beams should be done with a horizontal boom. That way you will not distort the pattern. This is not a problem with horizontal beams as the mast would be 90 degrees out of the beam's polarity plane and would not affect it. Just a question on something I have always wondered about: Why doesn't the portion of the mast pole that is below the boom affect the beams pattern? I understand about extending it and it acting like an additional element but shouldn't the same be true for the lower part? I know you can study a lifetime on antenna theory and still not even scratch the surface of all there is. Everything affects everything else. BC |
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Sandbagger
Administrator/The Boss
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Post by Sandbagger on Jan 21, 2009 7:39:56 GMT -5
If the mast (Unless it is not metallic) is allowed to extend through and above a vertical beam, the mast will act like another element (improperly sized and spaced) which will distort the beam's pattern and likely severely reduce your front:back ratio and/or forward gain. Any stacking that you do with vertical beams should be done with a horizontal boom. That way you will not distort the pattern. This is not a problem with horizontal beams as the mast would be 90 degrees out of the beam's polarity plane and would not affect it. Just a question on something I have always wondered about: Why doesn't the portion of the mast pole that is below the boom affect the beams pattern? I understand about extending it and it acting like an additional element but shouldn't the same be true for the lower part? I know you can study a lifetime on antenna theory and still not even scratch the surface of all there is. Everything affects everything else. BC And that is usually the question posed by observant individuals when this topic is brought up. The answer is "well.......". As I was told, there will still be "some" interaction with the mast, but since it is far smaller of an intrusion, the effect is negligable. If you are truly looking for maximum performance, with minimal pattern distortion, a vertical beam should be either end mounted (Not practical for 11 meter antennas), mounted on non-conductive mast (Not sure if such a thing exists which can handle the load), or stacked with a horizontal boom. |
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Post by BionicChicken on Jan 21, 2009 19:14:51 GMT -5
What I normally do is on an antenna that the elements mount on the side of the boom is to put them on the opposite side of the mast pole. I've never really seen any difference one way or the other. From talking to the engineers at Maco they said the antennas were designed with the mast in the equation and that you did not have to have the bottom of the elements clearing the top of the tower to get proper performance. I've seen people running big beam antennas with a 3' mast pole. Just enough out of the tower to hang the antenna on and the antennas worked well. Myself I like for the elements on my antenna to completely be above the tower. I mount the rotor at the bottom of the top section and have a bearing plate mounted on the top step to take the suspended weight off the rotor. My M107 mast pole was 13' out of the top of tower, SCH 80 pipe, it never has bent. Can't say the same for the antenna. Katrina broke it in half but it had been up for 14 years so I really can't complain.
BC
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Post by Phantom309 on Jan 21, 2009 20:43:12 GMT -5
WOW Id like to see a picture of that. the mast one one side of the beam question must be the reason they tell you you wont get youre match down below 1:5:1.
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