B
BOOTY MONSTER
Guest
when the math uses a dozen letters rather than numbers i don't stick around to embarrass myself . 
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Who knows about the Conjugate Match?
- Thread starter HomerBB
- Start date
I know what you mean, Booty. It's like what do you get when you cross a donkey and a horse. Well, I think it's a jack@$$. And it's sterile. . . Are we that desperate to ride that we see the sense in breeding an animal that is temporary? Ol' Red WAS a fine conjugate match, er mule.
Maybe someone will pass by again and save me from my silly ramblings.
In the meantime, I think I'll try to read more of the materials suggested.
Maybe someone will pass by again and save me from my silly ramblings.
In the meantime, I think I'll try to read more of the materials suggested.
Let me see:
assuming a non-dissipative transmission line means a loss-less transmission line then the theory is that if the capacitance of the load (antenna) is equal to the capacitance of the source (transceiver), and the capacitance of the transmission line is also the same and equal to load and source, then we assume the capacitance will be constant going both to and from the load and source (they change up based on whether the system is transmitting and/or receiving) then we have a big word for a matched system?
maybe I need to read some more
Is it getting stuffy to anyone else. . . gasp
assuming a non-dissipative transmission line means a loss-less transmission line then the theory is that if the capacitance of the load (antenna) is equal to the capacitance of the source (transceiver), and the capacitance of the transmission line is also the same and equal to load and source, then we assume the capacitance will be constant going both to and from the load and source (they change up based on whether the system is transmitting and/or receiving) then we have a big word for a matched system?
maybe I need to read some more
Is it getting stuffy to anyone else. . . gasp
Try Vicks Vapor Rub.
73
Jeff
( on Edit:
Maximum Power Transfer is another useful analysis method to ensure that the maximum amount of power will be dissipated in the load resistance when the value of the load resistance is exactly equal to the resistance of the power source.
The theorem results in maximum power transfer, and not maximum efficiency. If the resistance of the load is made larger than the resistance of the source, then efficiency is higher, since a higher percentage of the source power is transferred to the load, but the magnitude of the load power is lower since the total circuit resistance goes up.
If the load resistance is smaller than the source resistance, then most of the power ends up being dissipated in the source, and although the total power dissipated is higher, due to a lower total resistance, it turns out that the amount dissipated in the load is reduced.
The theorem states how to choose (so as to maximize power transfer) the load resistance, once the source resistance is given, not the opposite. It does not say how to choose the source resistance, once the load resistance is given. Given a certain load resistance, the source resistance that maximizes power transfer is always zero, regardless of the value of the load resistance.
The theorem can be extended to AC circuits that include reactance, and states that maximum power transfer occurs when the load impedance is equal to the complex conjugate of the source impedance.)
73
Jeff
( on Edit:
Maximum Power Transfer is another useful analysis method to ensure that the maximum amount of power will be dissipated in the load resistance when the value of the load resistance is exactly equal to the resistance of the power source.
The theorem results in maximum power transfer, and not maximum efficiency. If the resistance of the load is made larger than the resistance of the source, then efficiency is higher, since a higher percentage of the source power is transferred to the load, but the magnitude of the load power is lower since the total circuit resistance goes up.
If the load resistance is smaller than the source resistance, then most of the power ends up being dissipated in the source, and although the total power dissipated is higher, due to a lower total resistance, it turns out that the amount dissipated in the load is reduced.
The theorem states how to choose (so as to maximize power transfer) the load resistance, once the source resistance is given, not the opposite. It does not say how to choose the source resistance, once the load resistance is given. Given a certain load resistance, the source resistance that maximizes power transfer is always zero, regardless of the value of the load resistance.
The theorem can be extended to AC circuits that include reactance, and states that maximum power transfer occurs when the load impedance is equal to the complex conjugate of the source impedance.)
A for instance might help here, using our typical 50 Ohms output resistance of a transmitter.
We have defined the source resistance as 50 Ohms, no?
and we have determined the transmission line is 50 Ohms, no?
Where does this Zero source resistance thing come into play at my shack?
This provokes a question: How might this relate to whether or not we give too little or too much attention to SWR? ( I may be jumping the gun here)
Thanks for the vapor rub tip. I'm breathing better, but everyone is avoiding me now. . .
We have defined the source resistance as 50 Ohms, no?
and we have determined the transmission line is 50 Ohms, no?
Where does this Zero source resistance thing come into play at my shack?
This provokes a question: How might this relate to whether or not we give too little or too much attention to SWR? ( I may be jumping the gun here)
Thanks for the vapor rub tip. I'm breathing better, but everyone is avoiding me now. . .
Yes, but we are talking real world where the source impedance is never going to be zero.
You do worry too much about SWR. The instruments generally used are far too crude anyway.
You should never be as worried about conjugate match (or even impedance matching) as much as you should about power transfer.
This is why I prefer cross-needle meters when tuning antennas as I am able to maximize forward power as well as minimize reflection.
You do worry too much about SWR. The instruments generally used are far too crude anyway.
You should never be as worried about conjugate match (or even impedance matching) as much as you should about power transfer.
This is why I prefer cross-needle meters when tuning antennas as I am able to maximize forward power as well as minimize reflection.
Let's see if I'm getting the right interpretation of this.
Originally Posted by C2 View Post
"Yes, but we are talking real world where the source impedance is never going to be zero."
I have to agree with this, I've never seen a '0' impedance. I have seen a '0' difference in impedances, but that's a completely different thing.
"You do worry too much about SWR. The instruments generally used are far too crude anyway."
I agree -IF- you are trying to tune an antenna only using an SWR meter. It can only give you "it's" reading of SWR which can certainly not be a 50ohm Zero reactance reading of '1:1'. An SWR meter can't distinguish the difference, doesn't understand reactances at all. Like it or not, an SWR meter's positioning does definitely make a difference. That 'crude' doesn't refer to who made the SWR meter, but that meter's ability to tell you pertinent information.
"You should never be as worried about conjugate match (or even impedance matching) as much as you should about power transfer."
I agree. The whole idea of keeping impedances at least close to the same values (transmitter's output, feed lines, etc.) is to get the maximum transfer of power to the antenna, which should also have the same characteristic impedance as the rest of the antenna system. If the characteristic impedances of the components of that antenna system are all about the same, then the only losses would be in the 'resistive' nature of the feed line's length.
"This is why I prefer cross-needle meters when tuning antennas as I am able to maximize forward power as well as minimize reflection."
I like cross-needle meters too! They can tell you a lot more than just an SWR meter. You have the amount of forward power, the amount of reflected power, which if the meter is constructed properly means that where the two needles cross is the SWR scale.
All of the above is dealing only with impedance matching between components of the 'system', it does/says nothing about how well the antenna at the end of that 'system' is going to work, only that it is getting the most/best transfer of power. That's only 'half' of tuning an antenna. The other half deals with the antenna being resonant, having no un-neutralized reactance present -IN- the antenna. Reactances don't radiate anything, they contribute to a loss of radiation if they are found in an antenna. The idea is to get rid of them. If there are no reactances present in the antenna, and if the antenna's 'radiation resistance' is at least close to 50 ohms, then the thing will radiate very well.
that's where you start getting into another aspect of how well an antenna radiates. That deals with it's radiation pattern, which is always a function of the antenna's length. You can make almost anything resonant, you only have to add the correct amount of the right kind of reactance to the thing which will neutralize any reactance in it already... Ta Da... it's resonant! Is that good? Yes, as far as it goes. It'll radiate every bit of the power reaching it. But, what if that antenna is only a 'rubber-duck', which just doesn't have the bestest radiation pattern in the world? See where that's going? Antenna length/size does have much to do with the radiation pattern and where it'll put that radiated signal.
There's more to it, this is only a very 'condensed' explanation, not complete by any means. And since all of this deals with propagation, there ain't nothing 'set' in it, always going to be some variables as to which/what kind of antenna happens to be the best for any particular situation.
I'm tired of typing, there's more I wanna read on the forum before I have to go to work so I quit...
- 'Doc
Originally Posted by C2 View Post
"Yes, but we are talking real world where the source impedance is never going to be zero."
I have to agree with this, I've never seen a '0' impedance. I have seen a '0' difference in impedances, but that's a completely different thing.
"You do worry too much about SWR. The instruments generally used are far too crude anyway."
I agree -IF- you are trying to tune an antenna only using an SWR meter. It can only give you "it's" reading of SWR which can certainly not be a 50ohm Zero reactance reading of '1:1'. An SWR meter can't distinguish the difference, doesn't understand reactances at all. Like it or not, an SWR meter's positioning does definitely make a difference. That 'crude' doesn't refer to who made the SWR meter, but that meter's ability to tell you pertinent information.
"You should never be as worried about conjugate match (or even impedance matching) as much as you should about power transfer."
I agree. The whole idea of keeping impedances at least close to the same values (transmitter's output, feed lines, etc.) is to get the maximum transfer of power to the antenna, which should also have the same characteristic impedance as the rest of the antenna system. If the characteristic impedances of the components of that antenna system are all about the same, then the only losses would be in the 'resistive' nature of the feed line's length.
"This is why I prefer cross-needle meters when tuning antennas as I am able to maximize forward power as well as minimize reflection."
I like cross-needle meters too! They can tell you a lot more than just an SWR meter. You have the amount of forward power, the amount of reflected power, which if the meter is constructed properly means that where the two needles cross is the SWR scale.
All of the above is dealing only with impedance matching between components of the 'system', it does/says nothing about how well the antenna at the end of that 'system' is going to work, only that it is getting the most/best transfer of power. That's only 'half' of tuning an antenna. The other half deals with the antenna being resonant, having no un-neutralized reactance present -IN- the antenna. Reactances don't radiate anything, they contribute to a loss of radiation if they are found in an antenna. The idea is to get rid of them. If there are no reactances present in the antenna, and if the antenna's 'radiation resistance' is at least close to 50 ohms, then the thing will radiate very well.
that's where you start getting into another aspect of how well an antenna radiates. That deals with it's radiation pattern, which is always a function of the antenna's length. You can make almost anything resonant, you only have to add the correct amount of the right kind of reactance to the thing which will neutralize any reactance in it already... Ta Da... it's resonant! Is that good? Yes, as far as it goes. It'll radiate every bit of the power reaching it. But, what if that antenna is only a 'rubber-duck', which just doesn't have the bestest radiation pattern in the world? See where that's going? Antenna length/size does have much to do with the radiation pattern and where it'll put that radiated signal.
There's more to it, this is only a very 'condensed' explanation, not complete by any means. And since all of this deals with propagation, there ain't nothing 'set' in it, always going to be some variables as to which/what kind of antenna happens to be the best for any particular situation.
I'm tired of typing, there's more I wanna read on the forum before I have to go to work so I quit...
- 'Doc
Ya'll learnt' anything about "Conjugate Match" yet?
Here is the nity-gritty: http://www.ece.rutgers.edu/~orfanidi/ewa/ch12.pdf
Get your head's around this if you can.
Here is the nity-gritty: http://www.ece.rutgers.edu/~orfanidi/ewa/ch12.pdf
Get your head's around this if you can.