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#1
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simple dipole for newbie - copper, alum, or galv steel pipe?
"Dale Parfitt" wrote in message news:rMHOg.91$W13.22@trnddc05... "Zombie Wolf" wrote in message ... Make a Half - wave vertical with pipe. If the wall is dry wood, you can simply clamp it in place on the wall. You figure out the length of this antenna by the following formula 468 / freq (in MHZ) Hook the center conductor of the coax to the antenna, and then simply run a wire from the shield braid of the coax to a nearby ground. Presto. You now have a half - wave vertical. The end impedance of a half wave antenna is in the neighborhood of 1000--5000 Ohms depending on the diameter of the conductor; fatter conductors, lower Z The END impedance is not where you are making your connection. The impedance at the connection point on a half wave vertical is about 30 to 35 ohms. Not a perfect match , but certainly not 500 to 1 !. Connecting a coaxial cable to the bottom end of a half wave element and the shield to ground will then result in a V.S.W.R. of roughly 2500/50 or 500:1. You need to convert the feed Z to 5o Ohms either by: They didnt "convert" it when i ran a half wave whip on my car , and the shield was grounded to the chassis. I ran this for 15 years and never had an swr of over 1.5. My 40 meter vertical outside doesnt have an swr of 500, either, and it has worked well over the last 20 years. No stub matching is required in either case. Better tell this to the thousands of hams that have been running these antennas for the last 50 years ! No antenna matcher is needed, either (your lumped L or pi network). The formulas and the antenna itself came right out of the arrl handbook. 1. A quarter wave stub as in the popular J antenna 2. A lumped element L or Pi network Dale W4OP |
#2
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simple dipole for newbie - copper, alum, or galv steel pipe?
"Zombie Wolf" wrote in message ... "Dale Parfitt" wrote in message news:rMHOg.91$W13.22@trnddc05... "Zombie Wolf" wrote in message ... Make a Half - wave vertical with pipe. If the wall is dry wood, you can simply clamp it in place on the wall. You figure out the length of this antenna by the following formula 468 / freq (in MHZ) Hook the center conductor of the coax to the antenna, and then simply run a wire from the shield braid of the coax to a nearby ground. Presto. You now have a half - wave vertical. The end impedance of a half wave antenna is in the neighborhood of 1000--5000 Ohms depending on the diameter of the conductor; fatter conductors, lower Z The END impedance is not where you are making your connection. The impedance at the connection point on a half wave vertical is about 30 to 35 ohms. Not a perfect match , but certainly not 500 to 1 !. Connecting a coaxial cable to the bottom end of a half wave element and the shield to ground will then result in a V.S.W.R. of roughly 2500/50 or 500:1. You need to convert the feed Z to 5o Ohms either by: They didnt "convert" it when i ran a half wave whip on my car , and the shield was grounded to the chassis. I ran this for 15 years and never had an swr of over 1.5. My 40 meter vertical outside doesnt have an swr of 500, either, and it has worked well over the last 20 years. No stub matching is required in either case. Better tell this to the thousands of hams that have been running these antennas for the last 50 years ! No antenna matcher is needed, either (your lumped L or pi network). The formulas and the antenna itself came right out of the arrl handbook. So, you're telling me you have a 66' tall 40M vertical that is fed directly with coax? I would appreciate a model of the antenna in EZNEC or ELNEC or AO. In addition, the reference and year of the Handbook or any professional journal where it describes end feeding a half wave antenna directly with coaxial cable. Dale W4OP |
#3
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simple dipole for newbie - copper, alum, or galv steel pipe?
Yes, I do have a 66 foot vertical, that is suspended from about an 80 foot
tree out here, and i have been using it for a very long time. And the mobil antenna is still on the old truck, also. Out here in the country, they dont care what you put up for antennas. I also have a horizontal loop antenna out there that is 150 feet on each side. If you are so convinced that it doesnt work, then try it out. Its just that simple. Put a three foot one up in the attic, as i described, and see if it "fails to work".on the 155 mhz police band. Out here, we dont use EZNEC. We just put 'em up, tune 'em, and use 'em. The antennas I dexcribed here are well known to any novice operator (back when you had to know something about it). The half - wave vertical is problably one of the oldest antennas on the ham bands. It's not some "new idea" that i dreamed up.......... "Dale Parfitt" wrote in message news:caJOg.123$GO2.84@trnddc01... "Zombie Wolf" wrote in message ... "Dale Parfitt" wrote in message news:rMHOg.91$W13.22@trnddc05... "Zombie Wolf" wrote in message ... Make a Half - wave vertical with pipe. If the wall is dry wood, you can simply clamp it in place on the wall. You figure out the length of this antenna by the following formula 468 / freq (in MHZ) Hook the center conductor of the coax to the antenna, and then simply run a wire from the shield braid of the coax to a nearby ground. Presto. You now have a half - wave vertical. The end impedance of a half wave antenna is in the neighborhood of 1000--5000 Ohms depending on the diameter of the conductor; fatter conductors, lower Z The END impedance is not where you are making your connection. The impedance at the connection point on a half wave vertical is about 30 to 35 ohms. Not a perfect match , but certainly not 500 to 1 !. Connecting a coaxial cable to the bottom end of a half wave element and the shield to ground will then result in a V.S.W.R. of roughly 2500/50 or 500:1. You need to convert the feed Z to 5o Ohms either by: They didnt "convert" it when i ran a half wave whip on my car , and the shield was grounded to the chassis. I ran this for 15 years and never had an swr of over 1.5. My 40 meter vertical outside doesnt have an swr of 500, either, and it has worked well over the last 20 years. No stub matching is required in either case. Better tell this to the thousands of hams that have been running these antennas for the last 50 years ! No antenna matcher is needed, either (your lumped L or pi network). The formulas and the antenna itself came right out of the arrl handbook. So, you're telling me you have a 66' tall 40M vertical that is fed directly with coax? I would appreciate a model of the antenna in EZNEC or ELNEC or AO. In addition, the reference and year of the Handbook or any professional journal where it describes end feeding a half wave antenna directly with coaxial cable. Dale W4OP |
#4
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simple dipole for newbie - copper, alum, or galv steel pipe?
Ladies and gentlemen, here is a perfect example of CB mentality that has
plagued the radio hobby from the beginning. Someone here obviously doesn’t understand the fundamental nature of antennas but preaches bogus information as it was gospel. Maybe the half wavelength mobile antenna with the perfect match he refers to is his fiberglass loaded CB antenna, which is advertised in half, full, one and a half, and every combination of silly lengths to please CBrs as the dealers take their money. They do match ok, but are not the full length, end fed, very high impedance half wave antenna that he originally described in this thread. If you actually read the ARRL handbook you will see Mr. Wolf’s grievous mistakes. Bob Zombie Wolf wrote: Yes, I do have a 66 foot vertical, that is suspended from about an 80 foot tree out here, and i have been using it for a very long time. And the mobil antenna is still on the old truck, also. Out here in the country, they dont care what you put up for antennas. I also have a horizontal loop antenna out there that is 150 feet on each side. If you are so convinced that it doesnt work, then try it out. Its just that simple. Put a three foot one up in the attic, as i described, and see if it "fails to work".on the 155 mhz police band. Out here, we dont use EZNEC. We just put 'em up, tune 'em, and use 'em. The antennas I dexcribed here are well known to any novice operator (back when you had to know something about it). The half - wave vertical is problably one of the oldest antennas on the ham bands. It's not some "new idea" that i dreamed up.......... "Dale Parfitt" wrote in message news:caJOg.123$GO2.84@trnddc01... "Zombie Wolf" wrote in message ... "Dale Parfitt" wrote in message news:rMHOg.91$W13.22@trnddc05... "Zombie Wolf" wrote in message ... Make a Half - wave vertical with pipe. If the wall is dry wood, you can simply clamp it in place on the wall. You figure out the length of this antenna by the following formula 468 / freq (in MHZ) Hook the center conductor of the coax to the antenna, and then simply run a wire from the shield braid of the coax to a nearby ground. Presto. You now have a half - wave vertical. The end impedance of a half wave antenna is in the neighborhood of 1000--5000 Ohms depending on the diameter of the conductor; fatter conductors, lower Z The END impedance is not where you are making your connection. The impedance at the connection point on a half wave vertical is about 30 to 35 ohms. Not a perfect match , but certainly not 500 to 1 !. Connecting a coaxial cable to the bottom end of a half wave element and the shield to ground will then result in a V.S.W.R. of roughly 2500/50 or 500:1. You need to convert the feed Z to 5o Ohms either by: They didnt "convert" it when i ran a half wave whip on my car , and the shield was grounded to the chassis. I ran this for 15 years and never had an swr of over 1.5. My 40 meter vertical outside doesnt have an swr of 500, either, and it has worked well over the last 20 years. No stub matching is required in either case. Better tell this to the thousands of hams that have been running these antennas for the last 50 years ! No antenna matcher is needed, either (your lumped L or pi network). The formulas and the antenna itself came right out of the arrl handbook. So, you're telling me you have a 66' tall 40M vertical that is fed directly with coax? I would appreciate a model of the antenna in EZNEC or ELNEC or AO. In addition, the reference and year of the Handbook or any professional journal where it describes end feeding a half wave antenna directly with coaxial cable. Dale W4OP |
#5
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simple dipole for newbie - copper, alum, or galv steel pipe?
"Bob" wrote in message . .. Ladies and gentlemen, here is a perfect example of CB mentality that has plagued the radio hobby from the beginning. Someone here obviously doesn’t understand the fundamental nature of antennas but preaches bogus information as it was gospel. Maybe the half wavelength mobile antenna with the perfect match he refers to is his fiberglass loaded CB antenna, which is advertised in half, full, one and a half, and every combination of silly lengths to please CBrs as the dealers take their money. They do match ok, but are not the full length, end fed, very high impedance half wave antenna that he originally described in this thread. If you actually read the ARRL handbook you will see Mr. Wolf’s grievous mistakes. Bob Aah! A voice of reason. I well remember the CB ads re 1/2 wave and full wave antennas. As far as I could tell, the only thing half wave was maybe the overall length of wire if it were unwound and stretched out straight. Dale W4OP |
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