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In article ,
"HankG" no_one@invalid wrote: "Telamon" wrote in message .. . In article , "HankG" no_one@invalid wrote: My primary antenna is a 33 ft folded dipole made from 300 ohm twin lead and is mounted in my roof. It is coupled by a 300 to 75 ohm tv transformer to 75 ohm coax. The antenna is described in message 2471 of the Yahoo Rx-320 group and works fairly well. Recently, I acquired 3 rolls (40 ft each) of indoor 300 ohm coax, a closeout at Radio Shack. On checking my house diagram (drawing), I determined that I could run another antenna which could run about 100 feet if I include my garage. This is measured from left rear roof, through a wall, diagonally to front right garage (plus a 20 ft wrap on each end). I'd welcome any suggestions from the group on an antenna configuration such as dipole, folded dipole, twinlead converted to long wire (doubled back on itself), etc. This would be for SW reception, but MW would be a plus. Thanks. You could take two of those 40 foot pieces and make a 80 foot folded dipole antenna. Yes. The resonant frequency of an (un)folded dipole of 80 ft would be about 5.85 Mhz. My current antenna (resonant at 14.18 Mhz) uses a twinlead stub which supposedly confers a broader bandwidth. I have used it to monitor 160 meters and works fairly well in the single digits. Is there a formula for calculating stub length to give this 80 footer greater bandwidth? According to a Joe Carr antenna book I have this: In meters A - 141.8 / F MHz - Over all length or distance between outer shorts B - 122 / F MHz - distance between inner shorts In addition you could leave the outer shorts open then it would be: A - 142 / F MHz - Over all length or distance between outer ends B - 122 / F MHz - distance between inner shorts Example for 9.75 MHz is A = 14.56 meters B = 12.51 meters Some of the Radio Shack 300 / 75 ohm transformers are not much good below 10MHz. Interestingly, I acquired the transformers (2 on a card) at the local dollar store. Works fine. Well, it depends on which one you got your hands on. On some the S21 falls off below 10MHz and you were talking about a lower frequency antenna so just watch out for that. -- Telamon Ventura, California |
#2
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"Telamon" wrote in message ... In article , "HankG" no_one@invalid wrote: "Telamon" wrote in message .. . In article , "HankG" no_one@invalid wrote: My primary antenna is a 33 ft folded dipole made from 300 ohm twin lead and is mounted in my roof. It is coupled by a 300 to 75 ohm tv transformer to 75 ohm coax. The antenna is described in message 2471 of the Yahoo Rx-320 group and works fairly well. Recently, I acquired 3 rolls (40 ft each) of indoor 300 ohm coax, a closeout at Radio Shack. On checking my house diagram (drawing), I determined that I could run another antenna which could run about 100 feet if I include my garage. This is measured from left rear roof, through a wall, diagonally to front right garage (plus a 20 ft wrap on each end). I'd welcome any suggestions from the group on an antenna configuration such as dipole, folded dipole, twinlead converted to long wire (doubled back on itself), etc. This would be for SW reception, but MW would be a plus. Thanks. You could take two of those 40 foot pieces and make a 80 foot folded dipole antenna. Yes. The resonant frequency of an (un)folded dipole of 80 ft would be about 5.85 Mhz. My current antenna (resonant at 14.18 Mhz) uses a twinlead stub which supposedly confers a broader bandwidth. I have used it to monitor 160 meters and works fairly well in the single digits. Is there a formula for calculating stub length to give this 80 footer greater bandwidth? According to a Joe Carr antenna book I have this: In meters A - 141.8 / F MHz - Over all length or distance between outer shorts B - 122 / F MHz - distance between inner shorts In addition you could leave the outer shorts open then it would be: A - 142 / F MHz - Over all length or distance between outer ends B - 122 / F MHz - distance between inner shorts Example for 9.75 MHz is A = 14.56 meters B = 12.51 meters Some of the Radio Shack 300 / 75 ohm transformers are not much good below 10MHz. Interestingly, I acquired the transformers (2 on a card) at the local dollar store. Works fine. Well, it depends on which one you got your hands on. On some the S21 falls off below 10MHz and you were talking about a lower frequency antenna so just watch out for that. What is meant by inner and outer 'shorts'? HankG |
#3
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HankG wrote: "Telamon" wrote in message ... In article , "HankG" no_one@invalid wrote: "Telamon" wrote in message .. . In article , "HankG" no_one@invalid wrote: My primary antenna is a 33 ft folded dipole made from 300 ohm twin lead and is mounted in my roof. It is coupled by a 300 to 75 ohm tv transformer to 75 ohm coax. The antenna is described in message 2471 of the Yahoo Rx-320 group and works fairly well. Recently, I acquired 3 rolls (40 ft each) of indoor 300 ohm coax, a closeout at Radio Shack. On checking my house diagram (drawing), I determined that I could run another antenna which could run about 100 feet if I include my garage. This is measured from left rear roof, through a wall, diagonally to front right garage (plus a 20 ft wrap on each end). I'd welcome any suggestions from the group on an antenna configuration such as dipole, folded dipole, twinlead converted to long wire (doubled back on itself), etc. This would be for SW reception, but MW would be a plus. Thanks. You could take two of those 40 foot pieces and make a 80 foot folded dipole antenna. Yes. The resonant frequency of an (un)folded dipole of 80 ft would be about 5.85 Mhz. My current antenna (resonant at 14.18 Mhz) uses a twinlead stub which supposedly confers a broader bandwidth. I have used it to monitor 160 meters and works fairly well in the single digits. Is there a formula for calculating stub length to give this 80 footer greater bandwidth? According to a Joe Carr antenna book I have this: In meters A - 141.8 / F MHz - Over all length or distance between outer shorts B - 122 / F MHz - distance between inner shorts In addition you could leave the outer shorts open then it would be: A - 142 / F MHz - Over all length or distance between outer ends B - 122 / F MHz - distance between inner shorts Example for 9.75 MHz is A = 14.56 meters B = 12.51 meters Some of the Radio Shack 300 / 75 ohm transformers are not much good below 10MHz. Interestingly, I acquired the transformers (2 on a card) at the local dollar store. Works fine. Well, it depends on which one you got your hands on. On some the S21 falls off below 10MHz and you were talking about a lower frequency antenna so just watch out for that. What is meant by inner and outer 'shorts'? Well, I guess you've never seen some of those kids running around the 'hood'. Some of them wear their shorts on the inside, some of them wear them on the outside. dxAce Michigan USA |
#4
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What is meant by inner and outer 'shorts'?
Well, I guess you've never seen some of those kids running around the 'hood'. Some of them wear their shorts on the inside, some of them wear them on the outside. lol! -Brian /lives in the hood |
#5
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In article , dxAce
wrote: HankG wrote: "Telamon" wrote in message ... In article , "HankG" no_one@invalid wrote: "Telamon" wrote in message .. . In article , "HankG" no_one@invalid wrote: My primary antenna is a 33 ft folded dipole made from 300 ohm twin lead and is mounted in my roof. It is coupled by a 300 to 75 ohm tv transformer to 75 ohm coax. The antenna is described in message 2471 of the Yahoo Rx-320 group and works fairly well. Recently, I acquired 3 rolls (40 ft each) of indoor 300 ohm coax, a closeout at Radio Shack. On checking my house diagram (drawing), I determined that I could run another antenna which could run about 100 feet if I include my garage. This is measured from left rear roof, through a wall, diagonally to front right garage (plus a 20 ft wrap on each end). I'd welcome any suggestions from the group on an antenna configuration such as dipole, folded dipole, twinlead converted to long wire (doubled back on itself), etc. This would be for SW reception, but MW would be a plus. Thanks. You could take two of those 40 foot pieces and make a 80 foot folded dipole antenna. Yes. The resonant frequency of an (un)folded dipole of 80 ft would be about 5.85 Mhz. My current antenna (resonant at 14.18 Mhz) uses a twinlead stub which supposedly confers a broader bandwidth. I have used it to monitor 160 meters and works fairly well in the single digits. Is there a formula for calculating stub length to give this 80 footer greater bandwidth? According to a Joe Carr antenna book I have this: In meters A - 141.8 / F MHz - Over all length or distance between outer shorts B - 122 / F MHz - distance between inner shorts In addition you could leave the outer shorts open then it would be: A - 142 / F MHz - Over all length or distance between outer ends B - 122 / F MHz - distance between inner shorts Example for 9.75 MHz is A = 14.56 meters B = 12.51 meters Some of the Radio Shack 300 / 75 ohm transformers are not much good below 10MHz. Interestingly, I acquired the transformers (2 on a card) at the local dollar store. Works fine. Well, it depends on which one you got your hands on. On some the S21 falls off below 10MHz and you were talking about a lower frequency antenna so just watch out for that. What is meant by inner and outer 'shorts'? Well, I guess you've never seen some of those kids running around the 'hood'. Some of them wear their shorts on the inside, some of them wear them on the outside. Very funny! -- Telamon Ventura, California |
#6
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In article ,
"HankG" no_one@invalid wrote: "Telamon" wrote in message gy.com.. . In article , "HankG" no_one@invalid wrote: "Telamon" wrote in message gy.com.. . In article , "HankG" no_one@invalid wrote: My primary antenna is a 33 ft folded dipole made from 300 ohm twin lead and is mounted in my roof. It is coupled by a 300 to 75 ohm tv transformer to 75 ohm coax. The antenna is described in message 2471 of the Yahoo Rx-320 group and works fairly well. Recently, I acquired 3 rolls (40 ft each) of indoor 300 ohm coax, a closeout at Radio Shack. On checking my house diagram (drawing), I determined that I could run another antenna which could run about 100 feet if I include my garage. This is measured from left rear roof, through a wall, diagonally to front right garage (plus a 20 ft wrap on each end). I'd welcome any suggestions from the group on an antenna configuration such as dipole, folded dipole, twinlead converted to long wire (doubled back on itself), etc. This would be for SW reception, but MW would be a plus. Thanks. You could take two of those 40 foot pieces and make a 80 foot folded dipole antenna. Yes. The resonant frequency of an (un)folded dipole of 80 ft would be about 5.85 Mhz. My current antenna (resonant at 14.18 Mhz) uses a twinlead stub which supposedly confers a broader bandwidth. I have used it to monitor 160 meters and works fairly well in the single digits. Is there a formula for calculating stub length to give this 80 footer greater bandwidth? According to a Joe Carr antenna book I have this: In meters A - 141.8 / F MHz - Over all length or distance between outer shorts B - 122 / F MHz - distance between inner shorts In addition you could leave the outer shorts open then it would be: A - 142 / F MHz - Over all length or distance between outer ends B - 122 / F MHz - distance between inner shorts Example for 9.75 MHz is A = 14.56 meters B = 12.51 meters Some of the Radio Shack 300 / 75 ohm transformers are not much good below 10MHz. Interestingly, I acquired the transformers (2 on a card) at the local dollar store. Works fine. Well, it depends on which one you got your hands on. On some the S21 falls off below 10MHz and you were talking about a lower frequency antenna so just watch out for that. What is meant by inner and outer 'shorts'? If you use 300 ohm line to make the folded dipole then you "short" the two conductors on the ends. There are two designs above I wrote about. The first is a folded dipole so the ends are shorted and in order to make it more broadband you add two more shorts between the conductors a specific distance from the center. The second design only has the shorts placed at the "B" distance and the ends are left open. -- Telamon Ventura, California |
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