This ought to be worth discussion.

[BOOTY MONSTER]

VSWR - Microwave Encyclopedia - Microwaves101.com

"The voltage standing wave ratio is a measure of how well a load is impedance-matched to a source."

"stupid buffon" ..... you need to get better insults

p.s. honestly your insult deeply hurt my feelings . i am terribly insecure and being called mean names by faceless folks i don't respect at the other end of a internet connection could cause me a fit of depression and result in my needing professional help and meds

 

[W5LZ]

MrSuburban,
To clear things up a bit.
The only thing that SWR meter is doing (can do) is compare the impedance in front of it to the impedance behind it. The impedance in front of that meter is typically a combination of the feed line's impedance and the source's output impedance, which is supposed to be 50 ohms. The impedance behind that meter is a combination of the feed line's and the antenna's impedance. That's it, nothing mysterious or 'magical' about it. It's just a fact, that' how it is, you can't make it any simpler than that.
- 'Doc

I'm cheap and proud of it. Watch your mouth.

 

[BOOTY MONSTER]

Why are you asking me a question on how to tune your shit, I dont know what I am talking about remember.

what you think doesnt really matter, reality is what does.

just trying to clarify what you are saying .

and i agree %100 that reality rules over thinking . ill admit i may be wrong , its happened befor and it'll certianly happen again and again and again .
but i need a respected source (that excludes you) to confirm that this time .

anyhow ,

"where else have I tried to make any money?"
http://www.worldwidedx.com/cb-antennas/36412-modified-vector-4000-a-27.html#post259215

you,re too easy

but , we probably should lighten up before the thread get locked

 

[wavrider]

MrSuburban,
To clear things up a bit.
The only thing that SWR meter is doing (can do) is compare the impedance in front of it to the impedance behind it. The impedance in front of that meter is typically a combination of the feed line's impedance and the source's output impedance, which is supposed to be 50 ohms. The impedance behind that meter is a combination of the feed line's and the antenna's impedance. That's it, nothing mysterious or 'magical' about it. It's just a fact, that' how it is, you can't make it any simpler than that.
- 'Doc

I'm cheap and proud of it. Watch your mouth.

That is the best statement in this thread.

 

[Shockwave]

The VSWR meter does not do a thing to compare source impedance to the load side. It measures the ratio between forward power and reflected power. It really only measures RF voltage and is able to display this as power because it assumes it will be RF voltage into a 50 ohm load.

Thankfully VSWR has nothing to do with the source impedance otherwise it would be all over the board with every variation in amplitude. The 50 ohm standard is only relevant at maximum transmitter power. The typical SSB transmitter will vary it's output impedance anywhere from thousands of ohms, down to 50 ohms at full output.

Not to pick sides about tuning VSWR to the radio or the coax but it doesn't take a huge stretch of the imagination to see both of your points of view if both the transmitter and the coax are 50 ohms. However, it is more technically correct to say the VSWR is 1:1 when the antenna impedance matches the transmission lines since the source will vary with output level.

 

[loosecannon]

i must be crazy to get in the middle of this "discussion", but here goes.

from the things that i have read, MrSuburban is right about what SWR is. i think the arguments are a result of the "poetic license" taken by the authors of the articles that have been linked and pasted here.
it could be that we are all saying the same thing in different ways, i dont know.

"potential to radiate" was a stupid way of putting it, but what that guy meant was that just because a certain antenna shows a 50 ohm impedance, that doesnt mean that all the power delivered to it is being radiated.
(this is the exact argument against all the center loaded antenna junkies out there who think that because their antenna is 50 ohms, and a 1/4 wave whip is around 36 ohms; that their antenna gets out better)

i always say it the same way because people seem to understand it when i say
"my dummy load presents a perfect 50 ohm impedance, but it doesnt radiate well at all".

for those that are looking for another source, here is a quote from a certain handbook with the letters A, R, and L in the title:
"the ratio of maximum current to minimum current along a line is called the Standing Wave Ratio. the same ratio holds true for maximum voltage and minimum voltage. It is a measure of the mismatch between the load and the line, and is equal to 1 when the line is perfectly matched.
When the line is terminated into a purely resistive load, the Standing Wave Ratio is:
SWR= Zr/Zo
Zr-is the impedance of the load
Zo-is the characteristic impedance of the line"


as for the big "capacitor" on the antenna that started this thread, my opinion is that its there to make an antenna analyzer happy over a broader frequency range.
i think that the builder didnt like the 4-500khz bandwidth of his antenna design and added that "capacitor" to broaden the bandwidth by lowering the antenna's "Q".

you can always make an antenna cover a wider range of freqs, but you do that at the expense of its efficiency.

i am no antenna guru. i am currently reading about them in every spare second i have, and feel that i am learning a lot.
i do not feel that i "know my sh!t" yet.

the two main sources i have been trusting are the 1964 ARRL handbook, and a book issued by the Armed forces in 1953 called "Antennas and Radio Propagation".
this would be the book that any radioman in the army would have been given to study.
LC

 

[MrSuburban]

The VSWR meter does not do a thing to compare source impedance to the load side. It measures the ratio between forward power and reflected power. It really only measures RF voltage and is able to display this as power because it assumes it will be RF voltage into a 50 ohm load.

Thankfully VSWR has nothing to do with the source impedance otherwise it would be all over the board with every variation in amplitude. The 50 ohm standard is only relevant at maximum transmitter power. The typical SSB transmitter will vary it's output impedance anywhere from thousands of ohms, down to 50 ohms at full output.

Not to pick sides about tuning VSWR to the radio or the coax but it doesn't take a huge stretch of the imagination to see both of your points of view if both the transmitter and the coax are 50 ohms. However, it is more technically correct to say the VSWR is 1:1 when the antenna impedance matches the transmission lines since the source will vary with output level.

Exactly SWR doesnt compare the source impedance (radio, amplifier etc) but it does compare the line to the load. What is SWR when you have a 50 ohm antenna and the coax is 100 ohms. You have a 2:1 SWR. SWR is the relationship of coax to antenna, otherwise throw your Smith Chart out. You made my point. Thank You


END Of STORY


From ARRL
"For the case of resistive loads the SWR can be easily calculated as equal to
the (Load R)/Z0 or Z0/(Load R), whichever gives a result greater than or equal to 1.0."

 

[BOOTY MONSTER]

The VSWR meter does not do a thing to compare source impedance to the load side. It measures the ratio between forward power and reflected power. It really only measures RF voltage and is able to display this as power because it assumes it will be RF voltage into a 50 ohm load.

Thankfully VSWR has nothing to do with the source impedance otherwise it would be all over the board with every variation in amplitude. The 50 ohm standard is only relevant at maximum transmitter power. The typical SSB transmitter will vary it's output impedance anywhere from thousands of ohms, down to 50 ohms at full output.

Not to pick sides about tuning VSWR to the radio or the coax but it doesn't take a huge stretch of the imagination to see both of your points of view if both the transmitter and the coax are 50 ohms. However, it is more technically correct to say the VSWR is 1:1 when the antenna impedance matches the transmission lines since the source will vary with output level.

thanks

i must be crazy to get in the middle of this "discussion", but here goes.

from the things that i have read, MrSuburban is right about what SWR is. i think the arguments are a result of the "poetic license" taken by the authors of the articles that have been linked and pasted here.
it could be that we are all saying the same thing in different ways, i dont know.

"potential to radiate" was a stupid way of putting it, but what that guy meant was that just because a certain antenna shows a 50 ohm impedance, that doesnt mean that all the power delivered to it is being radiated.
(this is the exact argument against all the center loaded antenna junkies out there who think that because their antenna is 50 ohms, and a 1/4 wave whip is around 36 ohms; that their antenna gets out better)

i always say it the same way because people seem to understand it when i say
"my dummy load presents a perfect 50 ohm impedance, but it doesnt radiate well at all".

for those that are looking for another source, here is a quote from a certain handbook with the letters A, R, and L in the title:
"the ratio of maximum current to minimum current along a line is called the Standing Wave Ratio. the same ratio holds true for maximum voltage and minimum voltage. It is a measure of the mismatch between the load and the line, and is equal to 1 when the line is perfectly matched.
When the line is terminated into a purely resistive load, the Standing Wave Ratio is:
SWR= Zr/Zo
Zr-is the impedance of the load
Zo-is the characteristic impedance of the line"


as for the big "capacitor" on the antenna that started this thread, my opinion is that its there to make an antenna analyzer happy over a broader frequency range.
i think that the builder didnt like the 4-500khz bandwidth of his antenna design and added that "capacitor" to broaden the bandwidth by lowering the antenna's "Q".

you can always make an antenna cover a wider range of freqs, but you do that at the expense of its efficiency.

i am no antenna guru. i am currently reading about them in every spare second i have, and feel that i am learning a lot.
i do not feel that i "know my sh!t" yet.

the two main sources i have been trusting are the 1964 ARRL handbook, and a book issued by the Armed forces in 1953 called "Antennas and Radio Propagation".
this would be the book that any radioman in the army would have been given to study.
LC

and thank you too

so im wrong .


but i got a question ............ as usual , lol .
if source impedance doesn't effect vswr why do some of the guys with class c amps have issues with their vswr going up when they use it and have to play with coax lengths to make their meter happy ? i know the different coax lengths don't actually change the antennas tuning , but something is skewing the vswr measurement at the meter .

 

[MrSuburban]

i must be crazy to get in the middle of this "discussion", but here goes.

from the things that i have read, MrSuburban is right about what SWR is. i think the arguments are a result of the "poetic license" taken by the authors of the articles that have been linked and pasted here.
it could be that we are all saying the same thing in different ways, i dont know.

"potential to radiate" was a stupid way of putting it, but what that guy meant was that just because a certain antenna shows a 50 ohm impedance, that doesnt mean that all the power delivered to it is being radiated.
(this is the exact argument against all the center loaded antenna junkies out there who think that because their antenna is 50 ohms, and a 1/4 wave whip is around 36 ohms; that their antenna gets out better)

i always say it the same way because people seem to understand it when i say
"my dummy load presents a perfect 50 ohm impedance, but it doesnt radiate well at all".

for those that are looking for another source, here is a quote from a certain handbook with the letters A, R, and L in the title:
"the ratio of maximum current to minimum current along a line is called the Standing Wave Ratio. the same ratio holds true for maximum voltage and minimum voltage. It is a measure of the mismatch between the load and the line, and is equal to 1 when the line is perfectly matched.
When the line is terminated into a purely resistive load, the Standing Wave Ratio is:
SWR= Zr/Zo
Zr-is the impedance of the load
Zo-is the characteristic impedance of the line"

as for the big "capacitor" on the antenna that started this thread, my opinion is that its there to make an antenna analyzer happy over a broader frequency range.
i think that the builder didnt like the 4-500khz bandwidth of his antenna design and added that "capacitor" to broaden the bandwidth by lowering the antenna's "Q".

you can always make an antenna cover a wider range of freqs, but you do that at the expense of its efficiency.
i am no antenna guru. i am currently reading about them in every spare second i have, and feel that i am learning a lot.
i do not feel that i "know my sh!t" yet.

the two main sources i have been trusting are the 1964 ARRL handbook, and a book issued by the Armed forces in 1953 called "Antennas and Radio Propagation".
this would be the book that any radioman in the army would have been given to study.
LC

So what you said was quoted from the ARRL Book

SWR is a measure of the mismatch between the load and the line, and is equal to 1 when the line is perfectly matched.

Zr-is the impedance of the load
Zo-is the characteristic impedance of the line


You also said that increased bandwidth is the result of a less efficient antenna because of a lower Q.

Thank You Loose Cannon

LOL put that in your pipe and smoke it Mack

 

[Shockwave]

thanks



and thank you too

so im wrong .


but i got a question ............ as usual , lol .
if source impedance doesn't effect vswr why do some of the guys with class c amps have issues with their vswr going up when they use it and have to play with coax lengths to make their meter happy ? i know the different coax lengths don't actually change the antennas tuning , but something is skewing the vswr measurement at the meter .

The answer to this question can be found in the "High SWR with more power added" tread. The amplifiers in question would actually perform worse if they were biased up into class AB. It's all about instability in the cheap solid state amp that causes it to produce output on frequencies other then the fundamental. Mostly from self oscillation usually occurring within the band. Adding bias can make the problem increase to the point where enough self excitation is present that the amp stays keyed even when the transmitter is not.

 

[pro151]

The answer to this question can be found in the "High SWR with more power added" tread. The amplifiers in question would actually perform worse if they were biased up into class AB. It's all about instability in the cheap solid state amp that causes it to produce output on frequencies other then the fundamental. Mostly from self oscillation usually occurring within the band. Adding bias can make the problem increase to the point where enough self excitation is present that the amp stays keyed even when the transmitter is not.

Had that exact problem with a Palomar Elite 450HD when it was in the "High Power" mode.

 

[MrSuburban]

i don't feel bad . in fact im happy i didn't resort to petty and childish name calling to have a debate with you .


thanks shockwave , ill have to go read that thread a few times and try to get a clue

this forum isnt usually about that it is usually more of a technical nature I dont have to do that to make my point but I can if needed been thru many forum wars. Macks just sore I always get the better of him been that way for years somethings never change.


I dont think it is still in the database but at least about 7 or more years ago I was involved in a heated thread with Dr White a professor who had more electrical degrees behind his name, I said you could not check the output swr of a amp, he said you could (along with Doc, and about 50 guys like yourself)saying you could check swr of amp. I gave him a very simple test to do but he must not have had a tube amp or didnt know how to simulate the test he would just argue with me along with 50 wanna bees, I got tossed off the forum even though I was right cause everyone said i was wrong aand argued with me.

Take a tube amp and tune it into your antenna or whatever for max output , take a swr reading, now take the load knob this is the one the controls your output impedance and crank it to the right or left to mistune the amp's output impedance, go recheck the swr, it will be exactly the same as when you started because the SWR meter doesnt care or know what the source impedance is it checks the swr of coax to the load.

 

[loosecannon]

MrSuburban, i like the tube radio analogy, but how about this for a more modern take on it.

many people have been spreading coils in the output sections of their radios for many years.
we know that these coils are part of the half wave filter, whose job it is to filter harmonics while keeping the input and output impedances the same.
obviously, when you spread one of the coils in this half wave filter, you change its inductance which in turn ruins its ability to keep the input impedance the same as the output impedance.
this means that the output of your radio is no longer 50 ohms, but is off by some degree.
does this show up on your SWR meter? nope.
the SWR meter will still show the ratio of the antenna impedance to the impedance of the line going into the meter.

if this was not the case, people would have stopped spreading those coils long ago.
LC

 

[bob85]

we have been down this rooad before more than once:sad:,

vswr is a measure of the match between feedline and load/antenna,
theres no comparing impedance in front of the meter to whats behind it, thats doc's sciencefiction, just like his argument with HiDef over cm currents, pure fantasy island material, he argues with the laws of physics and gets away with it much of the time,
i have no control over the nonesense he posts nor can i make him go read up and learn,
he cannot post anything that backs up what he claims because its fiction,

high vswr is not caused by a mismatch between the transmitter and feedline as professor ken white argued with ccm,
he talked nonesense about everything he argued over from vswr to bias circuits, he had it wrong and it can easilly be proven with simple practical tests if reading respected material is too much of a hassle,

freedom of speech is good even entertaining but if you want to learn you must realise who is and is not talking shit,
i don't want anybody to believe me, i want them to do their own research from RESPECTED sources,

im pretty sure booty will look into it and im 100% sure doc will not, he will keep posting his usual diatribe without giving it a second thought

 

[MrSuburban]

we have been down this rooad before more than once:sad:,

vswr is a measure of the match between feedline and load/antenna,
theres no comparing impedance in front of the meter to whats behind it, thats doc's sciencefiction, just like his argument with HiDef over cm currents, pure fantasy island material, he argues with the laws of physics and gets away with it much of the time,
i have no control over the nonesense he posts nor can i make him go read up and learn,
he cannot post anything that backs up what he claims because its fiction,

high vswr is not caused by a mismatch between the transmitter and feedline as professor ken white argued with ccm,
he talked nonesense about everything he argued over from vswr to bias circuits, he had it wrong and it can easilly be proven with simple practical tests if reading respected material is too much of a hassle,

freedom of speech is good even entertaining but if you want to learn you must realise who is and is not talking shit,
i don't want anybody to believe me, i want them to do their own research from RESPECTED sources,

im pretty sure booty will look into it and im 100% sure doc will not, he will keep posting his usual diatribe without giving it a second thought

Ahhh those were the days






The Scarlett Pimpernel