SWR explained
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- เผยแพร่เมื่อ 12 ต.ค. 2021
- Find a PDF of this slideshow at pradiofun.com
I have been talking about SWR a lot in my videos but have never explained it.
This 9 slide presentation makes it easy to understand.
Some slides show the power loss out of the antenna based on the SWR reading.
How to read a cross needle SWR / Power meter.
And the effect of tuning the antenna.
I show the formulas but we don't use them. You will never have to use a VSWR formula.
Maybe on a Amateur Radio license test. You will know if you do from the FCC test question pool and can study for it.
Ham GMRS MURS CB - วิทยาศาสตร์และเทคโนโลยี
Best video on the subject I’ve seen!!
I will say this... most of the ham videos on the interwebs talk in so much code... that i think they forget there are people who know nothing about the hobby (me) that are trying to learn. So when somebody breaks down definitions (and more importantly, functions and practical applications)... i get jazzed.
So thanks!
That was understandable and I appreciate it.
That was very helpful. Thanks!
Thank you a very clear explanation !
Thank you... It's good enough for me to be happy... I'll keep looking for more. I'm bit nerdy.
Thank you. I have a lot to learn. Best wishes from NZ.
Awesome thank you..
OK, so SWR is a measurement of reflected power; so how and why is the power "reflected". Yes, I know it has to do with tuning the antenna so that the impedance matches between the antenna and the radio, but more directly, WHAT reflects the power, and how does tuning the antenna to its resonant length prevent that? Would installing a resistor at the ends of the antenna prevent this reflection?
Great video
How did you tune the antenna
HOW DID YOU TUNE THE ANTENNAE
This was great! Does using an antenna tuner mean you gain back the loss watts mentioned?
I too would love to know if an ATU will recover the lost power and the antenna will radiate it, or will the LC circuits in the ATU simply absorb the reflected power and protect the TX finals?
I will keep this simple so I may not be technically correct. 1) An "antenna tuner" does not increase antenna gain. 2) It does make the transmitter think everything is okay so it doesn't reduce TX power to protect the radio. 3) It does help with receiving signals also. This part seems like magic to me because it doesn't fix the resonance of the antenna.
Good explanation, thanks
Howdy.
I would think that a tuner provides a conjugate output impedance to the transmission line + antenna impedance. This, I understand, is the best power transfer setup. So, in my mind, a tuner will recover much of the reflected power and send it back to the antenna to radiate.
A tuner is an impedance trasformer. It transforms 50 ohms purely resistive to the coax. + antenna conjugate impedance.
My thinking is that a tuner does not bring the antenna into resonance. But it brings the coax. + antenna + tuner system into resonance.
Dave Casler takes this one step furher. According to him a tuner brings the coax. + antenna + tuner + environment total system into resonance.
However. I recognize there are two schools about this. The other persuasion claims that the reflected power is transformed into heat eventually.
Regards.
@@eugenepohjola258totally agree
i made a yagi from tape measures and did not measure anything. just eyeballed it. a signal came out when i put the baofeng on it. its mounted on my roof now and is continually transmitting dead air to the local repeater.
Even ineffective antenna transmit signals.
Tape measure yagis are a fun project.
great
Cos my field is in computers, i have some idea, , your wondering, what the hell is an SWR, SWR stands for "Standing Wave Ratio", the transmitting signal travels along the antenna (FORWARD) and refects at the end, returning down the antenna (REFECTED), the forward signal interferes with the reflected signal causing constructive or deconstructive interference, differant lengths create differant phases along the antenna, when a peek meets a peek there is max emission, and when a peek meets a trough there is zero emission, an SWR ratio of 1:1 is perfect constructive interference, where the cycle appears STATIONARY on the antenna, creating a perfect waxing and waning electo-magnetic field, as the electric field collapses, the magnetic field increases and vice versa, , ,Without that load absorbing energy, the energy instead appears as a high voltage or high current somewhere which may not be equipped to handle it, ,
So basically, an ideal 1:1 SWR will produce a low 50ohm resistance match where the antenna does work, the SWR is relatively constant along the feedline, the impedance will vary along the line unless it is perfectly terminated (that is, the SWR is 1.0 : 1). This is an important concept for impedance matching, because with a high SWR, the impedance at the final output transistor load inductor could be mainly higher, or lower than 50 ohms, and produce a high current that damages the finals, , ,
Ahh I see now why many radio operators damage there Nano meter
No it is not important to only check VSWR at the radio.
You should check it at the antenna with a VNA, yes you should have a radio meter 99% have one in the radio.
But checking VSWR after a a long run of coaxial cable is false as the coaxial cable absorbs some of the reflected power as coaxial cable loss.
Infact you can add coaxial cable length to soften the reflected power if you don't have a tuner but this will lower your ERP.
There are many myths and misconceptions in radio which are factually untrue. Reflected power is due to an impedance mismatch at a point in a circuit. A main issue in antenna systems is loss in the feedline. One very common misconception is that "high SWR damages the transmiiter". This is not true. The output circuit of a transmitter has an impedance matching circuit to match the low impedance of the output transistors to the higher impedance feedline. Reflected power arrives at the transmitter output and gets reflected again so that it is now in phase with the forward power. The aggregate effect is that most of the power produced by the transmitter will get radiated. The main factor of antenna performance is not SWR. With a perfect SWR (like you would get with a dummy load) you will still have feedline losses with coax. Some are better than others. To state that SWR above 1.5:1 will damage the radio is simply incorrect and promotes the misconception that SWR is enemy #1. I recommend every ham get a copy of the ARRL Antenna Book and read it. Another excellent book on the subject is titled Reflections by Walter Maxwell, an RF engineer who designed antenna systems for a living. It is a free download.
Next time point to where you are explaining, for those who are learning these calculations.
A 1.0.1 swr doesn't guarantee that all power is radiated at all , reflected power doesn't go back into the radio to damage it either,terrible info in this video
what is the truth?
@@mehmetdemir5655 reflected power adds to the forward power back to antenna and radiated, how much depends on the feedline, loss in the system can make swr low ,reflections by Walt Maxwell explains in great detail what's happening
@@paulm0hpd319 Oh, thank you for your reply
@@mehmetdemir5655 reflections 3 is a free download