If the radio ground and the antenna ground plane are isolated, yes you can swap and put the inner conductor to the ground plane and the outer conductor to the vertical extension. It works well that way. But there has to be an isolation like a roof mount ground plane. The inner and outer conductor currents are equal and opposite.
While it's true that the inner and outer conductors in a coaxial cable or a monopole antenna connection carry the same signal, they do so in very different ways, and their roles are not interchangeable. Here's why swapping them would make a difference: 1. Signal Propagation and Radiation Inner Conductor: In a monopole antenna, the inner conductor carries the signal to the radiating element (the monopole). This radiating element is designed to emit electromagnetic waves into the environment. Outer Conductor: The outer conductor (shield) in a coaxial cable is typically grounded. It acts as a reference plane (ground plane) and helps to return the signal in a controlled manner without radiating it. It also prevents interference and leakage of electromagnetic waves. Swapping these would mean the ground becomes the radiating element and the signal would no longer be properly transferred to the antenna structure designed to radiate. This would severely degrade or block the antenna’s ability to radiate efficiently. 2. Impedance Matching Coaxial cables and antennas are designed for a specific impedance, typically 50 ohms for RF systems. The coaxial cable's impedance depends on the ratio of the inner conductor's diameter to the outer conductor's diameter, as well as the material between them. Swapping the inner and outer conductors would dramatically change the impedance, leading to severe impedance mismatch. This mismatch results in reflection of the signal back toward the source, causing signal loss and inefficiency. I'll be releasing a video within the next ten days explaining "How Monopole antennas work" in detail. Hopefully it would answer any doubts you may still have. Thanks for the question. This is a very good question. I am sure many people may be thinking about the same.
isn't it easier to calculate 300 / frequency ? Thanks for the video. Always wonder how to find the impedence of an antenna and you showed me trough this video thanks
For 100 years 1/2 wavelength antennas have been used with balanced high impedance feedline. Say 600 ohms. By your description (approximately 12:1 swr) this would indicate that approximately 57% of the power is reflected at the feedpoint and the antenna system would therefore be inefficient. i.e. the reflected power is lost. But that is not the case. In fact if the transmitter can be matched into the feedline then at the feedpoint of the antenna we will measure a higher power than is generated, and when the reflected power is deducted the actual power radiated is the same as the transmitter generates. The reflected power is NOT lost and the system is in fact very high, nearly 100%.
@@TelecomTraining Sure it was, when you showed the chart of swr values up to 10:1. I'm talking about the mismatch at the feedpoint. That mismatch is defined by the impedance of the antenna load and the transmission line's Z0. Whether it is 10:1 or 12:1, the principle is the same and there is large reflected power. The question is, what happens to that power and your presentation implied that it was lost. If the generator is matched to the line it is NOT lost and the system as described is super high efficient
Hi Trevor, you explain this well, I found it very useful as a revision exercise and I'm sure new learners will really benefit from it well.
Thank you so much. I do appreciate that.
This was a good job, two over four when you reduce is now 1 over 2 . I away reduce to create the simplest terms.
Again nice job!😊
Cool, thanks👍
If the radio ground and the antenna ground plane are isolated, yes you can swap and put the inner conductor to the ground plane and the outer conductor to the vertical extension. It works well that way. But there has to be an isolation like a roof mount ground plane. The inner and outer conductor currents are equal and opposite.
While it's true that the inner and outer conductors in a coaxial cable or a monopole antenna connection carry the same signal, they do so in very different ways, and their roles are not interchangeable. Here's why swapping them would make a difference:
1. Signal Propagation and Radiation
Inner Conductor: In a monopole antenna, the inner conductor carries the signal to the radiating element (the monopole). This radiating element is designed to emit electromagnetic waves into the environment.
Outer Conductor: The outer conductor (shield) in a coaxial cable is typically grounded. It acts as a reference plane (ground plane) and helps to return the signal in a controlled manner without radiating it. It also prevents interference and leakage of electromagnetic waves.
Swapping these would mean the ground becomes the radiating element and the signal would no longer be properly transferred to the antenna structure designed to radiate. This would severely degrade or block the antenna’s ability to radiate efficiently.
2. Impedance Matching
Coaxial cables and antennas are designed for a specific impedance, typically 50 ohms for RF systems. The coaxial cable's impedance depends on the ratio of the inner conductor's diameter to the outer conductor's diameter, as well as the material between them.
Swapping the inner and outer conductors would dramatically change the impedance, leading to severe impedance mismatch. This mismatch results in reflection of the signal back toward the source, causing signal loss and inefficiency. I'll be releasing a video within the next ten days explaining "How Monopole antennas work" in detail. Hopefully it would answer any doubts you may still have. Thanks for the question. This is a very good question. I am sure many people may be thinking about the same.
isn't it easier to calculate 300 / frequency ?
Thanks for the video. Always wonder how to find the impedence of an antenna and you showed me trough this video
thanks
You're welcome.
For 100 years 1/2 wavelength antennas have been used with balanced high impedance feedline. Say 600 ohms. By your description (approximately 12:1 swr) this would indicate that approximately 57% of the power is reflected at the feedpoint and the antenna system would therefore be inefficient. i.e. the reflected power is lost. But that is not the case. In fact if the transmitter can be matched into the feedline then at the feedpoint of the antenna we will measure a higher power than is generated, and when the reflected power is deducted the actual power radiated is the same as the transmitter generates. The reflected power is NOT lost and the system is in fact very high, nearly 100%.
Hello, thanks for the input. However a reference to 600 ohms impedance or a ratio of 12:1 was never made in this video.
@@TelecomTraining Sure it was, when you showed the chart of swr values up to 10:1. I'm talking about the mismatch at the feedpoint. That mismatch is defined by the impedance of the antenna load and the transmission line's Z0. Whether it is 10:1 or 12:1, the principle is the same and there is large reflected power. The question is, what happens to that power and your presentation implied that it was lost. If the generator is matched to the line it is NOT lost and the system as described is super high efficient