You mentioned, sort of between the lines, that antenna 'tuners' don't actually 'tune' an antenna. Tuning an antenna really involves changing the antennas dimensions, hopefully to bring it into resonance with the frequency you're on. Even if you can do that, it probably won't present a 50+j0 ohm purely resistive complex impedance. For example, a folded dipole is closer to 300 ohm impedance.
An antenna 'tuner' or more correctly an antenna matching unit, is designed not to 'tune' the antenna, but the entire antenna, balun if used, coax feed and any static dissipating device, or lightning arrestor, antenna switch or whatever is between your rig and the antenna. What it really does is to provide a conjugate impedance that cancels the reactive component and adjust the real component of the complex impedance, so that your rig thinks it's looking into a purely resistive 50+j0 ohm complex load.
A tuner tunes what follows it. A remote tuner that feeds into the antenna will tune the antenna. The tuner that feeds into the coax will tune the coax and the antenna. It's not "fooling" anything.
Antennas can be modeled or measured to find the impedance (R+/-jX). We can think of that impedance value in 2 parts. The resistance and the reactance. Then we have the transmission line. The transmission line has a characteristic impedance. Typically, our coax is 50 ohms, but that may vary. Let's say it's 50 ohms here. We are interested in what that line sees at its output. Ideally, the load should be 50+j0 or something close. But let's say it's 150-j200. We need 2 things to happen here for efficiency.
1. The 200 ohms capacitive reactance needs to be cancelled by an inductor that looks like 200 ohms inductive at the desired frequency. This is to be in series with the antenna feed.
2. The 150 ohms resistive needs to be transformed to 50 ohms with a 3:1 impedance transformation. This is across the antenna feed.
Then we have a coax cable looking towards the antenna and it's seeing a 50+j0 load. The antenna is still 150-j200 but all we care about are 2 things.
1. We don't use any stinking resistors. The only resistance we want to cater to is the antenna radiation resistance. That's where we hear other stations and they can hear us. Also the coax cable is ideally seeing a resistance that is transformed into 50 ohms for the coax to see. In this case, we transform it by increasing the voltage and decreasing the current by 1.732 times.
2. The reactance THAT THE COAX SEES is zero. It's going to be purely resistive.
Saying that the tuner is fooling the transmitter is like saying the bicycle pedals are fooling your feet into thinking they are walking. Who knows what the transmitter is thinking, anyway? It's doing the work. The tuner properly used will transform the work being performed into the most useful power to the radiation resistance. If we look at the transmission line characteristic impedance, we can find the best efficiency by making sure the line sees its characteristic impedance at the input and at its output. Does a doublet work well? Yes. Is it efficient? No. It can be made to be more efficient. You have a 450+j0 characteristic impedance running into a 75+j0 antenna load. This is a 6:1 impedance imbalance. Hams usually will use a tuner at the windowline feedpoint. But you still have an imbalance at the antenna feedpoint.
Don't even get me started on 1:1 baluns. That's a whole other topic.
Percentage wise, the 75/80M band is the largest of the HF bands. 4MHz is 14.3% higher than 3.5MHz. 10 meters is only 6.1% higher from 28MHz to 29.7MHz. This percentage is what we see as the obstacle in getting a resonate antenna range for a dipole.
This whole "balun" thing is a farce. The resonant lines are balanced as long as they are resonant. They are not balanced if they are not resonant. When we look for a "balance", we are looking for currents that are opposite and equal and out of phase by 180 degrees.
SWR is the measurement of the peak voltage along the line compared to the valley standing voltage along the line. This ratio is the RESULT of the impedance matching of the load. It is not the impedance matching of the load. The antenna impedance is a complex value. R+/-jX. So if you have a resonant antenna that is 100 ohms and it's fed with a 50 ohm source, the SWR result is an easy 2:1. But with reactive loads, the calculation is more complicated.
Antennas have standing waves on them. We know what happens to those standing waves. They get radiated. Do we really think that standing waves on the transmission line will not radiate? Spoiler alert. They can radiate. Even coax can radiate. This is why some hams only deal with resonant antennas.
This whole "Back and forth" thing is misleading. We know that Walt Maxwell wrote of the "conjugate match" What that states is that the SIGNAL at the antenna FEEDPOINT is receiving the proper voltage/current (impedance) fed to the antenna. Now, how much voltage will be reflected from a matched load? Hmmm? Nothing should be reflected as ALL of the SIGNAL at that point should be radiated. Nothing reflected. Nothing bouncing. Bouncing only occurs when we don't use a tuner. There's tons more information on this topic. The final can heat up and get damaged because if there is not a good match, all of your signal is not getting radiated. It's back there heating up your final even more than what it's supposed to be.
It sounds like you are saying "Metal Oxide Semiconductor Field Effect Transistor" components are not actually "Metal"? Makes no sense. Metal is in the name.
I think I’ve said all of that - never said that the radio waves just stay on the line. However they do get reflected back and some of that energy does turn into heat. I’ve said that the energy does make it out to the antenna. Get some sleep, because you clearly didn’t hear what I said. ;)
Very true however the match box from my friend Steve WX2S can do about 900W on 160. I made it to 300 DXCC and DXCC on 8 bands with just 800 watts so 900 watts is nothing to sneeze at. Steve’s matching network is described in a QST article in September 2017 QST.
I need to stop accepting early Monday meetings!
9pm is bedtime when i have those early calls. Glad to see the broadcasts are continuing! The signal makes it into North Houston area quite well. :-)
Ria I have the PALSTAL AT2KD MTU good unit TNX for the talk 7388 de G6JMX
You mentioned, sort of between the lines, that antenna 'tuners' don't actually 'tune' an antenna. Tuning an antenna really involves changing the antennas dimensions, hopefully to bring it into resonance with the frequency you're on. Even if you can do that, it probably won't present a 50+j0 ohm purely resistive complex impedance. For example, a folded dipole is closer to 300 ohm impedance.
An antenna 'tuner' or more correctly an antenna matching unit, is designed not to 'tune' the antenna, but the entire antenna, balun if used, coax feed and any static dissipating device, or lightning arrestor, antenna switch or whatever is between your rig and the antenna. What it really does is to provide a conjugate impedance that cancels the reactive component and adjust the real component of the complex impedance, so that your rig thinks it's looking into a purely resistive 50+j0 ohm complex load.
ac2gl
That’s exactly the point. It’s to “fool” the transceiver. Sort of like glasses.
A tuner tunes what follows it. A remote tuner that feeds into the antenna will tune the antenna. The tuner that feeds into the coax will tune the coax and the antenna. It's not "fooling" anything.
Antennas can be modeled or measured to find the impedance (R+/-jX). We can think of that impedance value in 2 parts. The resistance and the reactance. Then we have the transmission line. The transmission line has a characteristic impedance. Typically, our coax is 50 ohms, but that may vary. Let's say it's 50 ohms here. We are interested in what that line sees at its output. Ideally, the load should be 50+j0 or something close. But let's say it's 150-j200. We need 2 things to happen here for efficiency.
1. The 200 ohms capacitive reactance needs to be cancelled by an inductor that looks like 200 ohms inductive at the desired frequency. This is to be in series with the antenna feed.
2. The 150 ohms resistive needs to be transformed to 50 ohms with a 3:1 impedance transformation. This is across the antenna feed.
Then we have a coax cable looking towards the antenna and it's seeing a 50+j0 load. The antenna is still 150-j200 but all we care about are 2 things.
1. We don't use any stinking resistors. The only resistance we want to cater to is the antenna radiation resistance. That's where we hear other stations and they can hear us. Also the coax cable is ideally seeing a resistance that is transformed into 50 ohms for the coax to see. In this case, we transform it by increasing the voltage and decreasing the current by 1.732 times.
2. The reactance THAT THE COAX SEES is zero. It's going to be purely resistive.
Saying that the tuner is fooling the transmitter is like saying the bicycle pedals are fooling your feet into thinking they are walking. Who knows what the transmitter is thinking, anyway? It's doing the work. The tuner properly used will transform the work being performed into the most useful power to the radiation resistance. If we look at the transmission line characteristic impedance, we can find the best efficiency by making sure the line sees its characteristic impedance at the input and at its output. Does a doublet work well? Yes. Is it efficient? No. It can be made to be more efficient. You have a 450+j0 characteristic impedance running into a 75+j0 antenna load. This is a 6:1 impedance imbalance. Hams usually will use a tuner at the windowline feedpoint. But you still have an imbalance at the antenna feedpoint.
Don't even get me started on 1:1 baluns. That's a whole other topic.
Jerry N9XR
Percentage wise, the 75/80M band is the largest of the HF bands. 4MHz is 14.3% higher than 3.5MHz. 10 meters is only 6.1% higher from 28MHz to 29.7MHz. This percentage is what we see as the obstacle in getting a resonate antenna range for a dipole.
This whole "balun" thing is a farce. The resonant lines are balanced as long as they are resonant. They are not balanced if they are not resonant. When we look for a "balance", we are looking for currents that are opposite and equal and out of phase by 180 degrees.
SWR is the measurement of the peak voltage along the line compared to the valley standing voltage along the line. This ratio is the RESULT of the impedance matching of the load. It is not the impedance matching of the load. The antenna impedance is a complex value. R+/-jX. So if you have a resonant antenna that is 100 ohms and it's fed with a 50 ohm source, the SWR result is an easy 2:1. But with reactive loads, the calculation is more complicated.
Antennas have standing waves on them. We know what happens to those standing waves. They get radiated. Do we really think that standing waves on the transmission line will not radiate? Spoiler alert. They can radiate. Even coax can radiate. This is why some hams only deal with resonant antennas.
This whole "Back and forth" thing is misleading. We know that Walt Maxwell wrote of the "conjugate match" What that states is that the SIGNAL at the antenna FEEDPOINT is receiving the proper voltage/current (impedance) fed to the antenna. Now, how much voltage will be reflected from a matched load? Hmmm? Nothing should be reflected as ALL of the SIGNAL at that point should be radiated. Nothing reflected. Nothing bouncing. Bouncing only occurs when we don't use a tuner. There's tons more information on this topic. The final can heat up and get damaged because if there is not a good match, all of your signal is not getting radiated. It's back there heating up your final even more than what it's supposed to be.
It sounds like you are saying "Metal Oxide Semiconductor Field Effect Transistor" components are not actually "Metal"? Makes no sense. Metal is in the name.
I could go on but it's beddy bye time for me.
Jerry N9XR
I think I’ve said all of that - never said that the radio waves just stay on the line. However they do get reflected back and some of that energy does turn into heat. I’ve said that the energy does make it out to the antenna. Get some sleep, because you clearly didn’t hear what I said. ;)
very few remote tuners for a 43ft vertical that handles 1.2K, MFJ had one, LDG had one but I haven’t seen it available in some time.
Very true however the match box from my friend Steve WX2S can do about 900W on 160. I made it to 300 DXCC and DXCC on 8 bands with just 800 watts so 900 watts is nothing to sneeze at. Steve’s matching network is described in a QST article in September 2017 QST.
KB2GCG