Silver Rod Question(s)
- Buick Mackane
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Silver Rod Question(s)
Antenna theory was never my strong point but i understand the basics. I'm trying to figure out how silver rods work, Yeah too much time on my hands So here's what's bugging me,
A halfwave dipole on 27mhz is roughly eighteen feet long, Nine feet either side. Now a halfwave silver rod is eighteen feet long, Shouldn't the main element only be nine feet long with the ground planes accounting for the other nine ?
The way im seeing it is like a lope sided dipole with one element being eighteen feet long and the other element being only nine feet long. There must be some kind of transformer converting the impedence
I'm probably overlooking the obvious but it is 2 am
So how do these magic wands work ?
A halfwave dipole on 27mhz is roughly eighteen feet long, Nine feet either side. Now a halfwave silver rod is eighteen feet long, Shouldn't the main element only be nine feet long with the ground planes accounting for the other nine ?
The way im seeing it is like a lope sided dipole with one element being eighteen feet long and the other element being only nine feet long. There must be some kind of transformer converting the impedence
I'm probably overlooking the obvious but it is 2 am
So how do these magic wands work ?
I Am the great cornholio are you threatening me ?
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Re: Silver Rod Question(s)
It's presumably a half wave vertical with a 49:1 UnUn at the base.
- Buick Mackane
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Re: Silver Rod Question(s)
Cheers would make sense. Kinda like a vertical long wire.
Last edited by Buick Mackane on 16 Feb 2022, 10:15, edited 1 time in total.
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I Am the great cornholio are you threatening me ?
- DX-Digger
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Re: Silver Rod Question(s)
There is a coil in the base to match the high Impedence and then a tap point which represents the 50Ohm impedence point
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- Buick Mackane
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Re: Silver Rod Question(s)
Ideal DX Digger I knew there had to be some impedance matching device in it,
Much appreciated
I Am the great cornholio are you threatening me ?
- NightProwler
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Re: Silver Rod Question(s)
I opened up an old silver rod years ago and the coil was a thing bit of wire wrapped around a small cardboard tube. Quality.
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- Buick Mackane
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Re: Silver Rod Question(s)
They just don't make them like that anymore richyNightProwler wrote: ↑16 Feb 2022, 14:17 I opened up an old silver rod years ago and the coil was a thing bit of wire wrapped around a small cardboard tube. Quality.
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Re: Silver Rod Question(s)
I'll tell you how I understand how they work, and hopefully it might help...Buick Mackane wrote: ↑16 Feb 2022, 02:12 Antenna theory was never my strong point but i understand the basics.
So how do these magic wands work ?
I think you have to consider why we use a half wave end fed like an antron or silver rod, it is pure convenience, a half wave dipole is so easy to put up horizontally, but not so easy vertically, which is what you want for CB. You can feed a half wave dipole at any point along its length and it will work just the same, the only thing that changes is the impedance. We use a half wave dipole and feed it in the middle because at the middle the impedance is close to 50 ohm, which matches to the 50 ohm coax which matches to the 50 ohm radio.
If you want to feed the dipole at the end, so we can put it at the top of a pole we have to feed it at the end. The impedance at the end is in the 1000's of ohms, so a bad match for the coax. The coil is there because at one end of the coil there is 1000's of ohms, the other end is connected to ground so 0 ohms, stands to reason that somewhere along the coil is 50 ohms, you just have to find it, and that's where you connect your coax.
Both antenna's should work the same, only difference is the loss in the matching coil whatever that may be.
- Buick Mackane
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Re: Silver Rod Question(s)
Good explanation 26OD00426OD004 wrote: ↑18 Feb 2022, 21:58I'll tell you how I understand how they work, and hopefully it might help...Buick Mackane wrote: ↑16 Feb 2022, 02:12 Antenna theory was never my strong point but i understand the basics.
So how do these magic wands work ?
I think you have to consider why we use a half wave end fed like an antron or silver rod, it is pure convenience, a half wave dipole is so easy to put up horizontally, but not so easy vertically, which is what you want for CB. You can feed a half wave dipole at any point along its length and it will work just the same, the only thing that changes is the impedance. We use a half wave dipole and feed it in the middle because at the middle the impedance is close to 50 ohm, which matches to the 50 ohm coax which matches to the 50 ohm radio.
If you want to feed the dipole at the end, so we can put it at the top of a pole we have to feed it at the end. The impedance at the end is in the 1000's of ohms, so a bad match for the coax. The coil is there because at one end of the coil there is 1000's of ohms, the other end is connected to ground so 0 ohms, stands to reason that somewhere along the coil is 50 ohms, you just have to find it, and that's where you connect your coax.
Both antenna's should work the same, only difference is the loss in the matching coil whatever that may be.
I Get it now, Really need to make more of an effort to brush up on my antenna knowledge,
Thanks for that
I Am the great cornholio are you threatening me ?
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Re: Silver Rod Question(s)
Happy to help, antenna theory still confuses me now, but I tryBuick Mackane wrote: ↑18 Feb 2022, 22:10Good explanation 26OD00426OD004 wrote: ↑18 Feb 2022, 21:58I'll tell you how I understand how they work, and hopefully it might help...Buick Mackane wrote: ↑16 Feb 2022, 02:12 Antenna theory was never my strong point but i understand the basics.
So how do these magic wands work ?
I think you have to consider why we use a half wave end fed like an antron or silver rod, it is pure convenience, a half wave dipole is so easy to put up horizontally, but not so easy vertically, which is what you want for CB. You can feed a half wave dipole at any point along its length and it will work just the same, the only thing that changes is the impedance. We use a half wave dipole and feed it in the middle because at the middle the impedance is close to 50 ohm, which matches to the 50 ohm coax which matches to the 50 ohm radio.
If you want to feed the dipole at the end, so we can put it at the top of a pole we have to feed it at the end. The impedance at the end is in the 1000's of ohms, so a bad match for the coax. The coil is there because at one end of the coil there is 1000's of ohms, the other end is connected to ground so 0 ohms, stands to reason that somewhere along the coil is 50 ohms, you just have to find it, and that's where you connect your coax.
Both antenna's should work the same, only difference is the loss in the matching coil whatever that may be.
I Get it now, Really need to make more of an effort to brush up on my antenna knowledge,
Thanks for that