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#1
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I take it that you are trying to learn and not just be argumentative.
If you read what I wrote, I said that in the antenna handbook that they finally have it right. Read the first three paragraphs under "TUNING TO A QUARTER WAVE" below. Regards Gary On Fri, 30 Apr 2004 00:07:54 -0400, "Doug Dotson" wrote: First you cite several instances that the ARRL treatment is wrong. Then you say the they finally got it right. Where are your references that substantiate either statement? Doug, k3qt s/v Callista "Gary Schafer" wrote in message .. . I tried to give an abbreviated synopsis of the subject and dispel some myths. I did not cover all the details. You need look no further than the ARRL itself for references. If you read the whole post you would see that near the bottom I credited the ARRL 2000 edition of their handbook, antenna section. The definition of "radiation resistance" is from there and the calculations of the example antenna with impedance's and voltages developed are directly from there. If you also look in the 18th edition 1997? of the ARRL antenna handbook chapter 16 "mobile and marine antennas", and probably later versions, you will see where they properly discuss loaded short antennas and what the coil does. Also if you look at the earlier post titled "Notes on short SSB antennas" you will find a reference to W8JI's web site where he discusses these very items in detail. He and many other engineers will tell you the same thing. I don't mean to discredit the ARRL but their statements in regard to tuning an antenna to a quarter wave in their older publications are misleading as evidenced by all the misconceptions that fly around. While that is a simplified explanation of what happens with the antenna matching, I suppose it was easier to propagate that (no pun intended) term for simplicity. But if you really want to understand what is going on it will get you into trouble in understanding as it is a conflict with what really happens. Regards Gary On Thu, 29 Apr 2004 20:25:53 -0400, "Doug Dotson" wrote: So, is this something you put together? How about some references? ARRL is a pretty reputable outfit. If you are going to dispute their writings, you should provide some some verifiable references. Doug, k3qt s/v Callista "Gary Schafer" wrote in message .. . This tries to explain how short SSB antennas operate and why. The discussion is concerning antennas that are shorter than a quarter wavelength. TUNING TO A QUARTER WAVE I looked through several older handbooks and antenna handbooks and found most of them professing what Larry is saying about "tuning an antenna to an electrical quarter wave." No wonder so many people have it wrong! The ARRL has been preaching this stuff for years. But in the same paragraphs they will speak to the "electrical length being very close to the physical length". Can't have it both ways! Even the 2000 ARRL handbook has it wrong. They finally got it right in their antenna handbook. Not once did I see reference to "tuning an antenna to an electrical quarter wave length. It may seem like semantics but there are a lot of people that get confused and think that when making the system resonant with a shorter antenna that the antenna is really the same as a quarter wave length antenna when there is a loading coil. It is far from that. Its radiation resistance and its feed point resistance are both much lower. An antennas electrical length is what it is by itself. Adding a coil to it to make it resonant will not change that. |
#2
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Gary,
I'm not trying to be contrary at all. So much of what floats around on this and other forums is totally anecdotal. When it comes to electrical engineering I expect a more formal and verifiable approach. More below. Doug, k3qt s/v Callista "Gary Schafer" wrote in message ... I take it that you are trying to learn and not just be argumentative. Absolutely. I'm tired of this argument. I'd like to be up to date in the current school of thought. Kind of like that myth that you need to line your hull with yards of copper foil as a counterpoise when emperical evedence says otherwise. If you read what I wrote, I said that in the antenna handbook that they finally have it right. But the only reference you cite is the ARRL Antenna Handbook. When you say they finally got it right, you must base that on something other than the handbook itself. When you said they were wrong for so many years, you gave no reference that supports that view. When you say they finally got it right you still gave no reference to support that suposition. So what it boils down to is that the handbook used to be wrong, now is right, and you are the judge as to what was right and wrong with no independently verifiable refererence to either position. I expect this from the government, but I cannot accept if from someone that appears have a reasonable engineering background. Read the first three paragraphs under "TUNING TO A QUARTER WAVE" below. I have read it. No reference other than the ARRL itself which used to be wrong and now is right. Regards Gary On Fri, 30 Apr 2004 00:07:54 -0400, "Doug Dotson" wrote: First you cite several instances that the ARRL treatment is wrong. Then you say the they finally got it right. Where are your references that substantiate either statement? Doug, k3qt s/v Callista "Gary Schafer" wrote in message .. . I tried to give an abbreviated synopsis of the subject and dispel some myths. I did not cover all the details. You need look no further than the ARRL itself for references. If you read the whole post you would see that near the bottom I credited the ARRL 2000 edition of their handbook, antenna section. The definition of "radiation resistance" is from there and the calculations of the example antenna with impedance's and voltages developed are directly from there. If you also look in the 18th edition 1997? of the ARRL antenna handbook chapter 16 "mobile and marine antennas", and probably later versions, you will see where they properly discuss loaded short antennas and what the coil does. Also if you look at the earlier post titled "Notes on short SSB antennas" you will find a reference to W8JI's web site where he discusses these very items in detail. He and many other engineers will tell you the same thing. I don't mean to discredit the ARRL but their statements in regard to tuning an antenna to a quarter wave in their older publications are misleading as evidenced by all the misconceptions that fly around. While that is a simplified explanation of what happens with the antenna matching, I suppose it was easier to propagate that (no pun intended) term for simplicity. But if you really want to understand what is going on it will get you into trouble in understanding as it is a conflict with what really happens. Regards Gary On Thu, 29 Apr 2004 20:25:53 -0400, "Doug Dotson" wrote: So, is this something you put together? How about some references? ARRL is a pretty reputable outfit. If you are going to dispute their writings, you should provide some some verifiable references. Doug, k3qt s/v Callista "Gary Schafer" wrote in message .. . This tries to explain how short SSB antennas operate and why. The discussion is concerning antennas that are shorter than a quarter wavelength. TUNING TO A QUARTER WAVE I looked through several older handbooks and antenna handbooks and found most of them professing what Larry is saying about "tuning an antenna to an electrical quarter wave." No wonder so many people have it wrong! The ARRL has been preaching this stuff for years. But in the same paragraphs they will speak to the "electrical length being very close to the physical length". Can't have it both ways! Even the 2000 ARRL handbook has it wrong. They finally got it right in their antenna handbook. Not once did I see reference to "tuning an antenna to an electrical quarter wave length. It may seem like semantics but there are a lot of people that get confused and think that when making the system resonant with a shorter antenna that the antenna is really the same as a quarter wave length antenna when there is a loading coil. It is far from that. Its radiation resistance and its feed point resistance are both much lower. An antennas electrical length is what it is by itself. Adding a coil to it to make it resonant will not change that. |
#3
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I am not sure just what you are missing here. Or maybe I am not
understanding your question. Again I am posting the reference pages below in the antenna handbook. Not once could I find in there that they stated that a loading coil on an antenna made it into a quarter wave antenna as did earlier versions of the antenna handbook and the regular handbook. That is why I say they finally got it right. Maybe you are questioning which one is right. In the earlier handbooks the subject was more or less glossed over with poor explanation of what happens in the antenna matching. The newer antenna handbook goes into more detail. I even tell you the pages! Also if you look at my earlier post "Notes on short SSB antennas" there is a link to W8JI's web site where he discusses the same stuff that I have. He tells you why a loaded antenna is still the same length electrically as an unloaded antenna. In that post there is a copy of part of his article that deals with this topic as I credited him with. For more details look at his web site. REFERENCE 1 If you also look in the 18th edition 1997? of the ARRL antenna handbook chapter 16 "mobile and marine antennas", and probably later versions, you will see where they properly discuss loaded short antennas and what the coil does. REFERENCE 2 Also if you look at the earlier post titled "Notes on short SSB antennas" you will find a reference to W8JI's web site where he discusses these very items in detail. He and many other engineers will tell you the same thing. Regards Gary On Fri, 30 Apr 2004 17:51:34 -0400, "Doug Dotson" wrote: Gary, I'm not trying to be contrary at all. So much of what floats around on this and other forums is totally anecdotal. When it comes to electrical engineering I expect a more formal and verifiable approach. More below. Doug, k3qt s/v Callista "Gary Schafer" wrote in message .. . I take it that you are trying to learn and not just be argumentative. Absolutely. I'm tired of this argument. I'd like to be up to date in the current school of thought. Kind of like that myth that you need to line your hull with yards of copper foil as a counterpoise when emperical evedence says otherwise. If you read what I wrote, I said that in the antenna handbook that they finally have it right. But the only reference you cite is the ARRL Antenna Handbook. When you say they finally got it right, you must base that on something other than the handbook itself. When you said they were wrong for so many years, you gave no reference that supports that view. When you say they finally got it right you still gave no reference to support that suposition. So what it boils down to is that the handbook used to be wrong, now is right, and you are the judge as to what was right and wrong with no independently verifiable refererence to either position. I expect this from the government, but I cannot accept if from someone that appears have a reasonable engineering background. Read the first three paragraphs under "TUNING TO A QUARTER WAVE" below. I have read it. No reference other than the ARRL itself which used to be wrong and now is right. Regards Gary On Fri, 30 Apr 2004 00:07:54 -0400, "Doug Dotson" wrote: First you cite several instances that the ARRL treatment is wrong. Then you say the they finally got it right. Where are your references that substantiate either statement? Doug, k3qt s/v Callista "Gary Schafer" wrote in message .. . I tried to give an abbreviated synopsis of the subject and dispel some myths. I did not cover all the details. You need look no further than the ARRL itself for references. If you read the whole post you would see that near the bottom I credited the ARRL 2000 edition of their handbook, antenna section. The definition of "radiation resistance" is from there and the calculations of the example antenna with impedance's and voltages developed are directly from there. If you also look in the 18th edition 1997? of the ARRL antenna handbook chapter 16 "mobile and marine antennas", and probably later versions, you will see where they properly discuss loaded short antennas and what the coil does. Also if you look at the earlier post titled "Notes on short SSB antennas" you will find a reference to W8JI's web site where he discusses these very items in detail. He and many other engineers will tell you the same thing. I don't mean to discredit the ARRL but their statements in regard to tuning an antenna to a quarter wave in their older publications are misleading as evidenced by all the misconceptions that fly around. While that is a simplified explanation of what happens with the antenna matching, I suppose it was easier to propagate that (no pun intended) term for simplicity. But if you really want to understand what is going on it will get you into trouble in understanding as it is a conflict with what really happens. Regards Gary On Thu, 29 Apr 2004 20:25:53 -0400, "Doug Dotson" wrote: So, is this something you put together? How about some references? ARRL is a pretty reputable outfit. If you are going to dispute their writings, you should provide some some verifiable references. Doug, k3qt s/v Callista "Gary Schafer" wrote in message .. . This tries to explain how short SSB antennas operate and why. The discussion is concerning antennas that are shorter than a quarter wavelength. TUNING TO A QUARTER WAVE I looked through several older handbooks and antenna handbooks and found most of them professing what Larry is saying about "tuning an antenna to an electrical quarter wave." No wonder so many people have it wrong! The ARRL has been preaching this stuff for years. But in the same paragraphs they will speak to the "electrical length being very close to the physical length". Can't have it both ways! Even the 2000 ARRL handbook has it wrong. They finally got it right in their antenna handbook. Not once did I see reference to "tuning an antenna to an electrical quarter wave length. It may seem like semantics but there are a lot of people that get confused and think that when making the system resonant with a shorter antenna that the antenna is really the same as a quarter wave length antenna when there is a loading coil. It is far from that. Its radiation resistance and its feed point resistance are both much lower. An antennas electrical length is what it is by itself. Adding a coil to it to make it resonant will not change that. |
#4
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I guess I'll pick up the latest Antenna Handbook and start reading.
Doug, k3qt s/v Callista "Gary Schafer" wrote in message ... I am not sure just what you are missing here. Or maybe I am not understanding your question. Again I am posting the reference pages below in the antenna handbook. Not once could I find in there that they stated that a loading coil on an antenna made it into a quarter wave antenna as did earlier versions of the antenna handbook and the regular handbook. That is why I say they finally got it right. Maybe you are questioning which one is right. In the earlier handbooks the subject was more or less glossed over with poor explanation of what happens in the antenna matching. The newer antenna handbook goes into more detail. I even tell you the pages! Also if you look at my earlier post "Notes on short SSB antennas" there is a link to W8JI's web site where he discusses the same stuff that I have. He tells you why a loaded antenna is still the same length electrically as an unloaded antenna. In that post there is a copy of part of his article that deals with this topic as I credited him with. For more details look at his web site. REFERENCE 1 If you also look in the 18th edition 1997? of the ARRL antenna handbook chapter 16 "mobile and marine antennas", and probably later versions, you will see where they properly discuss loaded short antennas and what the coil does. REFERENCE 2 Also if you look at the earlier post titled "Notes on short SSB antennas" you will find a reference to W8JI's web site where he discusses these very items in detail. He and many other engineers will tell you the same thing. Regards Gary On Fri, 30 Apr 2004 17:51:34 -0400, "Doug Dotson" wrote: Gary, I'm not trying to be contrary at all. So much of what floats around on this and other forums is totally anecdotal. When it comes to electrical engineering I expect a more formal and verifiable approach. More below. Doug, k3qt s/v Callista "Gary Schafer" wrote in message .. . I take it that you are trying to learn and not just be argumentative. Absolutely. I'm tired of this argument. I'd like to be up to date in the current school of thought. Kind of like that myth that you need to line your hull with yards of copper foil as a counterpoise when emperical evedence says otherwise. If you read what I wrote, I said that in the antenna handbook that they finally have it right. But the only reference you cite is the ARRL Antenna Handbook. When you say they finally got it right, you must base that on something other than the handbook itself. When you said they were wrong for so many years, you gave no reference that supports that view. When you say they finally got it right you still gave no reference to support that suposition. So what it boils down to is that the handbook used to be wrong, now is right, and you are the judge as to what was right and wrong with no independently verifiable refererence to either position. I expect this from the government, but I cannot accept if from someone that appears have a reasonable engineering background. Read the first three paragraphs under "TUNING TO A QUARTER WAVE" below. I have read it. No reference other than the ARRL itself which used to be wrong and now is right. Regards Gary On Fri, 30 Apr 2004 00:07:54 -0400, "Doug Dotson" wrote: First you cite several instances that the ARRL treatment is wrong. Then you say the they finally got it right. Where are your references that substantiate either statement? Doug, k3qt s/v Callista "Gary Schafer" wrote in message .. . I tried to give an abbreviated synopsis of the subject and dispel some myths. I did not cover all the details. You need look no further than the ARRL itself for references. If you read the whole post you would see that near the bottom I credited the ARRL 2000 edition of their handbook, antenna section. The definition of "radiation resistance" is from there and the calculations of the example antenna with impedance's and voltages developed are directly from there. If you also look in the 18th edition 1997? of the ARRL antenna handbook chapter 16 "mobile and marine antennas", and probably later versions, you will see where they properly discuss loaded short antennas and what the coil does. Also if you look at the earlier post titled "Notes on short SSB antennas" you will find a reference to W8JI's web site where he discusses these very items in detail. He and many other engineers will tell you the same thing. I don't mean to discredit the ARRL but their statements in regard to tuning an antenna to a quarter wave in their older publications are misleading as evidenced by all the misconceptions that fly around. While that is a simplified explanation of what happens with the antenna matching, I suppose it was easier to propagate that (no pun intended) term for simplicity. But if you really want to understand what is going on it will get you into trouble in understanding as it is a conflict with what really happens. Regards Gary On Thu, 29 Apr 2004 20:25:53 -0400, "Doug Dotson" wrote: So, is this something you put together? How about some references? ARRL is a pretty reputable outfit. If you are going to dispute their writings, you should provide some some verifiable references. Doug, k3qt s/v Callista "Gary Schafer" wrote in message .. . This tries to explain how short SSB antennas operate and why. The discussion is concerning antennas that are shorter than a quarter wavelength. TUNING TO A QUARTER WAVE I looked through several older handbooks and antenna handbooks and found most of them professing what Larry is saying about "tuning an antenna to an electrical quarter wave." No wonder so many people have it wrong! The ARRL has been preaching this stuff for years. But in the same paragraphs they will speak to the "electrical length being very close to the physical length". Can't have it both ways! Even the 2000 ARRL handbook has it wrong. They finally got it right in their antenna handbook. Not once did I see reference to "tuning an antenna to an electrical quarter wave length. It may seem like semantics but there are a lot of people that get confused and think that when making the system resonant with a shorter antenna that the antenna is really the same as a quarter wave length antenna when there is a loading coil. It is far from that. Its radiation resistance and its feed point resistance are both much lower. An antennas electrical length is what it is by itself. Adding a coil to it to make it resonant will not change that. |
#5
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![]() "Doug Dotson" wrote ... I guess I'll pick up the latest Antenna Handbook and start reading. Doug, k3qt s/v Callista The fundamental work on "small" antennas was done by a guy named Wheeler. After digging in the filing cabinet I found his paper from the proceedings of the I.R.E. (institute of radio engineers?) that preceded the IEEE. "Fundamental Limitations of Small Antennas" by Harold A. Wheeler fellow, I.R.E. December 1947 One insight is that a small antenna can theoretically be nearly as efficient as a 1/4 wave element but it is difficult to match to the small radiation resistance. (actually you match to the sum of the radiation and loss resistance). The efficiency is simply the ratio of radiation resistance to the sum of radiation plus loss resistance. A small loop antenna which looks inductive makes the job easier as you can build a low resistance loop and use high Q capacitors for tuning/matching. regards, -rick- |
#6
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"-rick-" wrote in
: "Doug Dotson" wrote ... I guess I'll pick up the latest Antenna Handbook and start reading. Doug, k3qt s/v Callista The fundamental work on "small" antennas was done by a guy named Wheeler. After digging in the filing cabinet I found his paper from the proceedings of the I.R.E. (institute of radio engineers?) that preceded the IEEE. "Fundamental Limitations of Small Antennas" by Harold A. Wheeler fellow, I.R.E. December 1947 One insight is that a small antenna can theoretically be nearly as efficient as a 1/4 wave element but it is difficult to match to the small radiation resistance. (actually you match to the sum of the radiation and loss resistance). The efficiency is simply the ratio of radiation resistance to the sum of radiation plus loss resistance. A small loop antenna which looks inductive makes the job easier as you can build a low resistance loop and use high Q capacitors for tuning/matching. regards, -rick- In 1947, matching the very low impedance feedpoint of a loaded vertical antenna was a problem. But, after the invention of the broadband iron powder toroids that are very efficient, magnetically at high frequencies, it's not much of a problem at all. At the base of my monster 1.8-30 Mhz 15' mobile ham antenna (4' ss base, 6" diameter monster loading coil, 3' mast, 36" capacitor hat and stainless whip on top cut so that shorting the whole coil resonates it at 14.250 Mhz) is a T-200-2 powered iron toroid core wrapped with insulating fiberglass tape and 12 turns of bare #10 copper. The core is mounted in a plastic construction box between the posts of banana jacks that are soldered to the outside of each turn so banana plugs can select the turns ratio. One end of the coil is connected to "ground", the chassis of the car. Any reasonable RF grounding system would hook there on a boat. The coax from the transceiver's 650 watt, 12V linear amp is terminated with a banana plug to select the input tap, and a short length of braided strap goes between a banana plug and the bottom feed point of the antenna for the output tap. Best match occurs when the lowest reflected power occurs on the SWR meter of the linear amp (or transceiver with the linear out of the circuit). On my antenna, on the 3.5-4 Mhz ham band for instance, the input tap is across the entire 12 turns and the antenna is tapped 4 turns above the ground point. SWR at resonance is perfect, 1:1, and large corona arcs occur at the top of the whip tip and bent around ends of the 8 spokes of the 36" capacitor hat, made of stainless welding rod welded to two large flatwashers at the center. Signals are very comparible to any fixed station here running the same power. Cars passing blow horns and shout, "Your Antenna Is On Fire!", out their windows. It will light up a flourescent tube in your hand at 10' away, easily. The square of the turns ratio is 9:1 so the antenna's impedance is somewhere around 6 ohms or so at the feedpoint. The 650 W amp melted the solder joints on the core using #12 wire for the turns, so I went to #10 which is about as thick as I can go with 12 evenly spaced turns without shorts. #10 wire gets too hot to touch, but doesn't melt solder any more...(c; A second similar toroid autotransformer is mounted in another box with 24 turns of #12 next to the first. It is used for the 160 Meter band (1.8-2 Mhz). A second loading coil on top of the first (3" diam, 200T) adds sufficient inductance to tune the 15' antenna down to 1.8 Mhz, but at 650 watts there is so much corona arcing it makes the SWR readings go crazy so power is reduced to 300W or whatever the humidity around the antenna can stand at that particular moment. If one were to forego the old untuned wire/tuner marine antenna configuration and go with a real tuned vertical, this toroid autotransformer will very efficiently match the very low base impedance to the 50 ohm transceiver across the 2-30 Mhz HF band. The car's electrical wiring resonates around 3.9 Mhz, causing all the dash lights to glow brightly with SSB modulation on their own, to the amazement of even ham radio passengers. Thank God old Mercedes 220D diesels have no electronics in them! Many hams have gone to a remotely-tuned mobile antenna that uses a powered motor to move the tap on a center loading coil. Here's what it looks like: http://www.qth.com/n7lyy/about.html It uses a screwdriver DC motor to move the loading coil up and down against a large contactor and will tune the entire band. If a boater were to make the whip longer than the 66" limit for cars, it would be even more efficient with less coil turns below 12 Mhz. 66" is so it will tune 29.7 Mhz, the highest HF ham band boaters don't need. This antenna system would easily mount on a stern rail, using the rail as groundplane if it were all connected together, and would tune from the radio while watching the SWR meter on the radio (or output power meter which would just tune for maximum output power). Larry W4CSC Some day I might try this antenna using the handrails of the boat as ground plane. It's gotta work better than the stupid untuned backstay and inefficient antenna tuner. It certainly results in much better signal reports. |
#7
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On Tue, 04 May 2004 15:08:08 -0000, Larry W4CSC
wrote: The square of the turns ratio is 9:1 so the antenna's impedance is somewhere around 6 ohms or so at the feedpoint. The 650 W amp melted the solder joints on the core using #12 wire for the turns, so I went to #10 If one were to forego the old untuned wire/tuner marine antenna configuration and go with a real tuned vertical, this toroid autotransformer will very efficiently match the very low base impedance to the 50 ohm transceiver across the 2-30 Mhz HF band. Larry W4CSC Some day I might try this antenna using the handrails of the boat as ground plane. It's gotta work better than the stupid untuned backstay and inefficient antenna tuner. It certainly results in much better signal reports. Your feed point resistance may be 6 ohms but about 5.8 to 5.9 ohms of that are coil resistance. The radiation resistance of the 15 foot whip on 3.5 mhz is in the order of .1 ohm. So about 97% of your power is going up in heat in the coils. Only a couple percent of the power is making it to the antenna to be radiated. Of 650 watts only around 20 watts makes it to the antenna. A full quarter wave length vertical has a radiation and feed point resistance of around 36 ohms. Much easier to get power into than a .1 ohm 15 foot antenna. Oh, don't forget to add in all the ground loss resistance too. Less power to the antenna yet. If you can get your feed point resistance down to around 1 ohm then you will get about 10% of your power into the 15 foot antenna! Regards Gary |
#8
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Here's some more information on screwdriver HF antennas:
http://www.qsl.net/k4kwh/ http://www.hsantennas.com/ http://www.kj7u.com/ http://www.ko6yd.com/sam/index.htm (screwdriver antenna memory tuner) http://www.mfjenterprises.com/produc...rodid=MFJ-1662 http://texasbugcatcher.com/ (my antenna uses Henry's coils but is not a screwdriver.) http://www.mindspring.com/~k4poz/ As you can see, these antennas are very respected by the finicky ham radio mobile operators. They'll ALL tune ALL the marine bands. Larry W4CSC |
#9
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I wonder if Gary writes for World Radio magazine under the pen name of Kurt
N Sturba? Doug K7ABX "Gary Schafer" wrote in message ... I take it that you are trying to learn and not just be argumentative. If you read what I wrote, I said that in the antenna handbook that they finally have it right. Read the first three paragraphs under "TUNING TO A QUARTER WAVE" below. Regards Gary On Fri, 30 Apr 2004 00:07:54 -0400, "Doug Dotson" wrote: First you cite several instances that the ARRL treatment is wrong. Then you say the they finally got it right. Where are your references that substantiate either statement? Doug, k3qt s/v Callista "Gary Schafer" wrote in message .. . I tried to give an abbreviated synopsis of the subject and dispel some myths. I did not cover all the details. You need look no further than the ARRL itself for references. If you read the whole post you would see that near the bottom I credited the ARRL 2000 edition of their handbook, antenna section. The definition of "radiation resistance" is from there and the calculations of the example antenna with impedance's and voltages developed are directly from there. If you also look in the 18th edition 1997? of the ARRL antenna handbook chapter 16 "mobile and marine antennas", and probably later versions, you will see where they properly discuss loaded short antennas and what the coil does. Also if you look at the earlier post titled "Notes on short SSB antennas" you will find a reference to W8JI's web site where he discusses these very items in detail. He and many other engineers will tell you the same thing. I don't mean to discredit the ARRL but their statements in regard to tuning an antenna to a quarter wave in their older publications are misleading as evidenced by all the misconceptions that fly around. While that is a simplified explanation of what happens with the antenna matching, I suppose it was easier to propagate that (no pun intended) term for simplicity. But if you really want to understand what is going on it will get you into trouble in understanding as it is a conflict with what really happens. Regards Gary On Thu, 29 Apr 2004 20:25:53 -0400, "Doug Dotson" wrote: So, is this something you put together? How about some references? ARRL is a pretty reputable outfit. If you are going to dispute their writings, you should provide some some verifiable references. Doug, k3qt s/v Callista "Gary Schafer" wrote in message .. . This tries to explain how short SSB antennas operate and why. The discussion is concerning antennas that are shorter than a quarter wavelength. TUNING TO A QUARTER WAVE I looked through several older handbooks and antenna handbooks and found most of them professing what Larry is saying about "tuning an antenna to an electrical quarter wave." No wonder so many people have it wrong! The ARRL has been preaching this stuff for years. But in the same paragraphs they will speak to the "electrical length being very close to the physical length". Can't have it both ways! Even the 2000 ARRL handbook has it wrong. They finally got it right in their antenna handbook. Not once did I see reference to "tuning an antenna to an electrical quarter wave length. It may seem like semantics but there are a lot of people that get confused and think that when making the system resonant with a shorter antenna that the antenna is really the same as a quarter wave length antenna when there is a loading coil. It is far from that. Its radiation resistance and its feed point resistance are both much lower. An antennas electrical length is what it is by itself. Adding a coil to it to make it resonant will not change that. |
#10
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"Doug" wrote in
.net: I wonder if Gary writes for World Radio magazine under the pen name of Kurt N Sturba? Doug K7ABX Hee hee....(c; World Radio is the definitive answer to all broadcast engineering questions.... 73, Larry W4CSC |
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