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#1
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Alain
The ARRL Antenna Hand book is considered a standard http://www.arrl.org/catalog/?categor...+Propaga tion L. B. Cebik, W4RNL has a weath of antenna information - see URL: http://www.cebik.com/radio.html Lots of Antenna projects on the web (homebrew) at URL: http://ac6v.com/antprojects.htm This links to many other web sites -- kinda of a roundup of antenna web sites Also a very popular author of Antennas is William I. Orr -- His books can be found on Amazon.com http://www.amazon.com/W6Sai-Hf-Anten...e=UTF8&s=books 73 and good radiating CL "Joaquin Tall" wrote in message ... Hello All, I have just gotten my tech license and am eager to get my station up and running. I am starting on a shoestring; currently, I have no equipment whatsoever and don't know what I should buy just yet. In absence of a rig, I am now studying to pass my General license exam next month. I am very interested in building my own HF/VHF/UHF antennas. I've seen the ARRL books, but I was hoping that you good folks might have some favorite websites, book titles or magazine issues [old or new] that you'd be willing to pass along that could get me started. Many thanks for taking the time to respond! 73's to you all! Alain...San Diego |
#2
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![]() "Caveat Lector" wrote in message ... Alain The ARRL Antenna Hand book is considered a standard http://www.arrl.org/catalog/?categor...+Propaga tion L. B. Cebik, W4RNL has a weath of antenna information - see URL: http://www.cebik.com/radio.html Lots of Antenna projects on the web (homebrew) at URL: http://ac6v.com/antprojects.htm This links to many other web sites -- kinda of a roundup of antenna web sites Also a very popular author of Antennas is William I. Orr -- His books can be found on Amazon.com http://www.amazon.com/W6Sai-Hf-Anten...e=UTF8&s=books 73 and good radiating CL "Joaquin Tall" wrote in message ... Hello All, I have just gotten my tech license and am eager to get my station up and running. I am starting on a shoestring; currently, I have no equipment whatsoever and don't know what I should buy just yet. In absence of a rig, I am now studying to pass my General license exam next month. I am very interested in building my own HF/VHF/UHF antennas. I've seen the ARRL books, but I was hoping that you good folks might have some favorite websites, book titles or magazine issues [old or new] that you'd be willing to pass along that could get me started. Many thanks for taking the time to respond! 73's to you all! Alain...San Diego Some elementary books have some strange explanations, this is because they are trying to explain something to someone who probably doesnt have the proper background yet.They are well meaning and are a great help at getting the novice on the air. One such mistake is calling a 4 ft long antenna that has a coil to make it resonate on the 10M band a "10M loaded 1/4 wavelength antenna" . Actually this would be an 1/8 wl antenna more or less. So watch out Jimmie |
#3
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Jimmie D wrote:
One such mistake is calling a 4 ft long antenna that has a coil to make it resonate on the 10M band a "10M loaded 1/4 wavelength antenna". They should be more careful and specify that they are talking about electrical lengths, not physical lengths. For instance, the following stub is electrically 90 degrees long even though it is physically only 38 degrees long. 1/4WL stub -------------------+-------- 27 deg, Z0=500 11 deg, Z0=50 Incidentally, this is how a loaded antenna can be 90 degrees long electrically while being physically much shorter than 90 degrees. -- 73, Cecil http://www.w5dxp.com |
#4
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"Cecil Moore":
Jimmie D wrote: One such mistake is calling a 4 ft long antenna that has a coil to make it resonate on the 10M band a "10M loaded 1/4 wavelength antenna". They should be more careful and specify that they are talking about electrical lengths, not physical lengths. ______________ They also should point out that, although a radiator physically/electrically shorter than needed for first self-resonance can be "loaded" to resonance, this does not mean that loaded and self-resonant radiators perform equally well in an installed system. In some applications there can be as much as a 100:1 difference in their radiated powers, for a given power at the transmitter output connector. RF |
#5
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Richard Fry wrote:
"Cecil Moore": Jimmie D wrote: One such mistake is calling a 4 ft long antenna that has a coil to make it resonate on the 10M band a "10M loaded 1/4 wavelength antenna". They should be more careful and specify that they are talking about electrical lengths, not physical lengths. They also should point out that, although a radiator physically/electrically shorter than needed for first self-resonance can be "loaded" to resonance, this does not mean that loaded and self-resonant radiators perform equally well in an installed system. In some applications there can be as much as a 100:1 difference in their radiated powers, for a given power at the transmitter output connector. Good point, Richard. An antenna's ability to "load" is proportional to its electrical length. An antenna's ability to radiate seems to be proportional to the physical length of the antenna that is carrying the highest current. In 75m shootouts, the mobile antennas with the loading coil furtherest away from the feedpoint (closest to top-loaded) generally won the shootout. -- 73, Cecil http://www.w5dxp.com |
#6
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"Cecil Moore" :
An antenna's abilty to "load" is proportional to its electrical length. An antenna's ability to radiate seems to be proportional to the physical length of the antenna that is carrying the highest current. __________ Perhaps unexpectedly, the intrinsic pattern and directivity of a physically/electrically short, unloaded monopole radiator are not greatly different than those of a self-resonant 1/4-wave monopole. The big problem with an unloaded, short radiator is the reactance at its feedpoint, which means that very little current will flow into the short radiator from any practical r-f source. But for the current that DOES flow in it, its radiation performance will not be much different than that of a self-resonant 1/4-wave monopole, at that same current flow (as NEC will show). Using a "loading" reactance to resonate the radiator allows maximum power transfer from the r-f source into the feedpoint. But the remaining issue is the low radiation resistance of the short radiator even when it is resonant, which is a small fraction of the other series resistances in the antenna system (ground and coil loss, mostly). As a result, much of the available transmitter power produces heat rather than EM radiation. RF |
#7
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![]() "Richard Fry" wrote in message ... "Cecil Moore" : An antenna's abilty to "load" is proportional to its electrical length. An antenna's ability to radiate seems to be proportional to the physical length of the antenna that is carrying the highest current. __________ Perhaps unexpectedly, the intrinsic pattern and directivity of a physically/electrically short, unloaded monopole radiator are not greatly different than those of a self-resonant 1/4-wave monopole. The big problem with an unloaded, short radiator is the reactance at its feedpoint, which means that very little current will flow into the short radiator from any practical r-f source. But for the current that DOES flow in it, its radiation performance will not be much different than that of a self-resonant 1/4-wave monopole, at that same current flow (as NEC will show). Using a "loading" reactance to resonate the radiator allows maximum power transfer from the r-f source into the feedpoint. But the remaining issue is the low radiation resistance of the short radiator even when it is resonant, which is a small fraction of the other series resistances in the antenna system (ground and coil loss, mostly). As a result, much of the available transmitter power produces heat rather than EM radiation. RF I had an electronics instructor (not sure what he knew about antennas) say thet there was a 10/90 rule about antennas. That an antenna 10 % as long as a 1/4 wl will radiate 90%as well, wile he didnt say it I assume this means with all other sources of loss minimized. Is this anywhere near true? /Jimmie |
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