Good explanation. But you forgot to mention that when the reflected power reaches the antenna tuner and will travel back onto the coax line, it will under go a phase shift, in the same way this happened at the antenna. Love your videos's...
One way to demonstrate the amount of power of a given transmission would be to set up and a practical experiment where SWR is measured and, "theoretical" loss is calculated. Then measure peak envelope power at the antenna with a meter specifically used for that purpose. If, for example, the SWR formula predicts a 10 watt loss on a 100 watt transmission, but no loss is seen at the antenna this effectively busts the myth and should end further debate.
Another good SWR video! I explain it many different ways. Some students get it with one explanation some another way. Keep it up! Many can visualize water waves hitting a breakwater and bouncing back toward the sea. When the crest of a reflected water wave passes the crest of an incoming wave (sometimes called swells) they add together and the peak is twice as high as one alone. I can also show standing waves with a rope secured to a wall. By shaking it up and down I can send waves to the wall and they are reflected back. With the proper frequency you can create a standing wave.
I love your videos also!! I try to tell hams what you are saying here but they mostly don't believe me. I use random wire antennas with good quality coax (LMR 400) and my antennas works all bands from 160 to 6 meters with very little additional loss as compared to a dipole. I really like the benefit of using all the bands. Robert K5TPC
Just come across your channel and several other ham radio channel and binge watching at moment ,what ive noticed is the confusion surrounding the reflected power adding to the forward power, people are misinterpreting this as extra power being created
Mark, I am very happy that I found your channel. I always questioned the reading on my Palstar SWR/watt meter. If there was loss, why was it added to the total watts out. Got my answers! I have a question for you. I have limited space for the ground radials on my DX commander antenna. Is it ok for me to cross over 3 or 4 radials to obtain a good spread as close to 360 degrees as possible. I haven’t found any resources that speaks to a cross over.
Do whatever you have to do to get as much wire in the ground as you can. It's only an RF ground so I don't see why crossing over would cause any problems. Some guys use a metal screen so there's plenty of crossover wires. Get a minimum of 12 radials on the ground and more if you can. Don't knock yourself silly trying to get a 1:1 SWR. Follow his instructions, use a tuner and good coax and don't worry about SWR unless it's really high. Everything affects SWR - soil conductivity, nearby objects and so on.
@@NoMoreRadioMyths Thank you so much! Currently I have 24 and the antenna rocks. I did employ a good 3 days getting the SWRs as close to 1:1 as I could. So I am not using a tuner. Call me OCD, but in my professional life, I always went for as much precision as possible. It’s also fun and a good learning experience to tune the elements. I really did not need to do that, but I am retired and this happened to be a productive activity and a challenge, so I went for it! LOL
@BMCTackle At 24, you should be fine. Callum (your antenna's designer), did a video on the topic, back in the day. Pretty much found that after 16 radials, the difference between that, and say, several hundred radials would be about 3 dB more gain.
@@dereks2042 I saw that video a while back. Given my location, soil, etc. This set up works great, but reception Is a challenge. The additional gain while small, helps. This is like your last lime and you are getting ready to pop open a Corona, your going to squeeze out as much of that last lime. LMAO
The initial power that travels to the mismatched load is recorded by the watt meter. Because of the 3:1 mismatch some of that is reflected back to the source as you state. That is also recorded as reflected power. Magic happens here according to your description because the transmitter and transmission line are not mismatched - in fact they are perfectly matched. The magic is all the energy from the mismatch is reflected back to the antenna anyway according to your mythbusting claim. Or there isn't a perfect match at the point of reflection back to the antenna and is shorted or open or mismatched. And that is impossible else the energy recorded by the watt meter would have never left the transmitter. When the reflected power bounces back toward the antenna (its third time down the wire) it faces the same example 3:1 swr that met it on its first trip and some of it is reflected back to the transmitter (4th trip) and is again reflected toward the antenna (5th trip) and sees that same 3:1 SWR and a portion is reflected back to the transmitter. All these trips lose a little to the coax losses. It is finally not trivial. In every trip the wattmeter is recording all the forward energy that is traveling to the antenna, and also all the reflected energy traveling back to the transmitter.
Wrong. The transmitter does not see a 50 ohm transmission line. A transmission line with standing waves has different impedances along its length and can be considered an impedance transformer. Only a 50 ohm transmission line with a 50 ohm load will also be 50 ohms at the other end. You made other errors too but I'm leaving that for others to correct.
@@NoMoreRadioMyths Do you understand that not having a 50 ohm impedance means your power meter is not giving you accurate information and that it is not possible in that circumstance to know what absolute power is transferred? They are accurate only when all impedances are matched (no reactive component). All you can know is the ratio of forward to reflected power but without any absolute value of that power. But you did not address the multiple reflections that are continuously happening in the 3:1 scenario and how that affects your description of what is happening.
Don't know where in fl. you are but you are my elmer. at 67 years old i just got into Ham. Live in citrus co. and if you are close would love to pick your brain to get my extra.
Love your Amateur Radio myth buster videos, so needed. Thank You.
Good explanation. But you forgot to mention that when the reflected power reaches the antenna tuner and will travel back onto the coax line, it will under go a phase shift, in the same way this happened at the antenna.
Love your videos's...
Yes you are correct. Tried to keep it as simple as possible. I'm going to do another one on reflection gain so phase shift comes into play there.
One way to demonstrate the amount of power of a given transmission would be to set up and a practical experiment where SWR is measured and, "theoretical" loss is calculated. Then measure peak envelope power at the antenna with a meter specifically used for that purpose. If, for example, the SWR formula predicts a 10 watt loss on a 100 watt transmission, but no loss is seen at the antenna this effectively busts the myth and should end further debate.
Another good SWR video! I explain it many different ways. Some students get it with one explanation some another way. Keep it up!
Many can visualize water waves hitting a breakwater and bouncing back toward the sea. When the crest of a reflected water wave passes the crest of an incoming wave (sometimes called swells) they add together and the peak is twice as high as one alone.
I can also show standing waves with a rope secured to a wall. By shaking it up and down I can send waves to the wall and they are reflected back. With the proper frequency you can create a standing wave.
I love your videos also!! I try to tell hams what you are saying here but they mostly don't believe me. I use random wire antennas with good quality coax (LMR 400) and my antennas works all bands from 160 to 6 meters with very little additional loss as compared to a dipole. I really like the benefit of using all the bands. Robert K5TPC
This makes total sense
I tried to clear some of this stuff up years ago on my blog. I gave up. Glad to see you’re being persistent! Cheers and 73 de AD5GG.
I know exactly what you mean. People can believe what they want. I'm going to hang with it cuz its fun and I'm learning.
Just come across your channel and several other ham radio channel and binge watching at moment ,what ive noticed is the confusion surrounding the reflected power adding to the forward power, people are misinterpreting this as extra power being created
Yes I addressed that in a previous video on reflected power but probably worth a separate video to show there is no magic power increase.
Now I want to take my LDG AT-1000 ProII Autotuner somewhere to have the case plated with 24k gold! 🤣🤣🤣
KD8EFQ/73
Mark, I am very happy that I found your channel. I always questioned the reading on my Palstar SWR/watt meter. If there was loss, why was it added to the total watts out. Got my answers!
I have a question for you. I have limited space for the ground radials on my DX commander antenna. Is it ok for me to cross over 3 or 4 radials to obtain a good spread as close to 360 degrees as possible.
I haven’t found any resources that speaks to a cross over.
Do whatever you have to do to get as much wire in the ground as you can. It's only an RF ground so I don't see why crossing over would cause any problems. Some guys use a metal screen so there's plenty of crossover wires. Get a minimum of 12 radials on the ground and more if you can. Don't knock yourself silly trying to get a 1:1 SWR. Follow his instructions, use a tuner and good coax and don't worry about SWR unless it's really high. Everything affects SWR - soil conductivity, nearby objects and so on.
@@NoMoreRadioMyths Thank you so much! Currently I have 24 and the antenna rocks. I did employ a good 3 days getting the SWRs as close to 1:1 as I could. So I am not using a tuner. Call me OCD, but in my professional life, I always went for as much precision as possible. It’s also fun and a good learning experience to tune the elements. I really did not need to do that, but I am retired and this happened to be a productive activity and a challenge, so I went for it! LOL
@BMCTackle At 24, you should be fine. Callum (your antenna's designer), did a video on the topic, back in the day. Pretty much found that after 16 radials, the difference between that, and say, several hundred radials would be about 3 dB more gain.
@@dereks2042 I saw that video a while back. Given my location, soil, etc. This set up works great, but reception Is a challenge. The additional gain while small, helps. This is like your last lime and you are getting ready to pop open a Corona, your going to squeeze out as much of that last lime. LMAO
The OCD's are going to be very angry. I guess they'll just have to obsess about something else. Like maybe resonance or coax type.
The initial power that travels to the mismatched load is recorded by the watt meter. Because of the 3:1 mismatch some of that is reflected back to the source as you state. That is also recorded as reflected power. Magic happens here according to your description because the transmitter and transmission line are not mismatched - in fact they are perfectly matched. The magic is all the energy from the mismatch is reflected back to the antenna anyway according to your mythbusting claim. Or there isn't a perfect match at the point of reflection back to the antenna and is shorted or open or mismatched. And that is impossible else the energy recorded by the watt meter would have never left the transmitter.
When the reflected power bounces back toward the antenna (its third time down the wire) it faces the same example 3:1 swr that met it on its first trip and some of it is reflected back to the transmitter (4th trip) and is again reflected toward the antenna (5th trip) and sees that same 3:1 SWR and a portion is reflected back to the transmitter. All these trips lose a little to the coax losses. It is finally not trivial. In every trip the wattmeter is recording all the forward energy that is traveling to the antenna, and also all the reflected energy traveling back to the transmitter.
Wrong. The transmitter does not see a 50 ohm transmission line. A transmission line with standing waves has different impedances along its length and can be considered an impedance transformer. Only a 50 ohm transmission line with a 50 ohm load will also be 50 ohms at the other end. You made other errors too but I'm leaving that for others to correct.
@@NoMoreRadioMyths Do you understand that not having a 50 ohm impedance means your power meter is not giving you accurate information and that it is not possible in that circumstance to know what absolute power is transferred? They are accurate only when all impedances are matched (no reactive component). All you can know is the ratio of forward to reflected power but without any absolute value of that power. But you did not address the multiple reflections that are continuously happening in the 3:1 scenario and how that affects your description of what is happening.
Don't know where in fl. you are but you are my elmer. at 67 years old i just got into Ham. Live in citrus co. and if you are close would love to pick your brain to get my extra.
Appreciate that but I don't know what's on the test now. You'd be better off with a study book or something similar. :)
Thank you😎 KQ4OHB
Thank you too!