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#1
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Taking one band with another and one direction with another, the difference
between a Windom and G5RV will be entirely undetectable. They will both have somewhat poorer performance than a simple random length dipole of about the same length and height fed over a random length, high impedance, any Zo, open-wire line. Following the study you have given to the subject, you may be disappointed at the responses to your question, But you did ask. And there's no reason why you should be deterred from experimenting with either or both types of antenna. You will then be at least as wise as us Old Wive's. If you should like playing with just a few numbers then amuse yourself with small programs DIPOLE3 and ENDFEED. Download from website below in a few seconds and run immediately. They provide lots of data but the most important thing is the single number - radiating efficiency! --- .................................................. .......... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp .................................................. .......... |
#2
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Thanks for all comments.
I did a mistakle in my specs because they are no traps on the windom (I confused with W4DZZ). In fact I thought that both designs being wire antennas of almost the same length, they 'd display the same radiation pattern at a few percent. But I was focused on the shortest segment (1/3) of the windom and wonder whether it could cause or not additional problems or display drawbacks compared to a real dipole... In all case I will test it in 2 weeks. Problem with dipole3, the influence of a shorter segment is not taken into account. I don't know if that could be important, probably not much, but it 'd have been interesting to add some additional parameters like the length of each segment and the tilt of the tilt too to get a more accurate result. Addition: My believe is founded. I just find some radiation patterns and comments in the ARRL antenna book ch7-8. The windom is much more omnidirectional than a dipole. They say that "the system (windom) takes advantage of the asymmetry of the horizontal wires to induce current onto the braid of the vertical coax section.... The radiation pattern... tends to fill in the deep nulls that 'd be present ... if horizontally center fed". globally they consider that the windom give better results due to the omnidirectional pattern or so than a true dipole. Anyway, if I have the courage I will try to simulate the windom in Multinec. Thanks for the help Thierry, ON4SKY "Reg Edwards" wrote in message ... Taking one band with another and one direction with another, the difference between a Windom and G5RV will be entirely undetectable. They will both have somewhat poorer performance than a simple random length dipole of about the same length and height fed over a random length, high impedance, any Zo, open-wire line. Following the study you have given to the subject, you may be disappointed at the responses to your question, But you did ask. And there's no reason why you should be deterred from experimenting with either or both types of antenna. You will then be at least as wise as us Old Wive's. If you should like playing with just a few numbers then amuse yourself with small programs DIPOLE3 and ENDFEED. Download from website below in a few seconds and run immediately. They provide lots of data but the most important thing is the single number - radiating efficiency! --- .................................................. ......... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp .................................................. ......... |
#3
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Thierry wrote:
Thanks for all comments. I did a mistakle in my specs because they are no traps on the windom (I confused with W4DZZ). In fact I thought that both designs being wire antennas of almost the same length, they 'd display the same radiation pattern at a few percent. But I was focused on the shortest segment (1/3) of the windom and wonder whether it could cause or not additional problems or display drawbacks compared to a real dipole... In all case I will test it in 2 weeks. Problem with dipole3, the influence of a shorter segment is not taken into account. I don't know if that could be important, probably not much, but it 'd have been interesting to add some additional parameters like the length of each segment and the tilt of the tilt too to get a more accurate result. Addition: My believe is founded. I just find some radiation patterns and comments in the ARRL antenna book ch7-8. The windom is much more omnidirectional than a dipole. They say that "the system (windom) takes advantage of the asymmetry of the horizontal wires to induce current onto the braid of the vertical coax section.... The radiation pattern... tends to fill in the deep nulls that 'd be present ... if horizontally center fed". globally they consider that the windom give better results due to the omnidirectional pattern or so than a true dipole. Anyway, if I have the courage I will try to simulate the windom in Multinec. Thanks for the help Thierry, ON4SKY "Reg Edwards" wrote in message ... Taking one band with another and one direction with another, the difference between a Windom and G5RV will be entirely undetectable. They will both have somewhat poorer performance than a simple random length dipole of about the same length and height fed over a random length, high impedance, any Zo, open-wire line. Following the study you have given to the subject, you may be disappointed at the responses to your question, But you did ask. And there's no reason why you should be deterred from experimenting with either or both types of antenna. You will then be at least as wise as us Old Wive's. If you should like playing with just a few numbers then amuse yourself with small programs DIPOLE3 and ENDFEED. Download from website below in a few seconds and run immediately. They provide lots of data but the most important thing is the single number - radiating efficiency! --- ................................................ ........... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp ................................................ ........... Hi Thierry: The only draw back of the off center fed dipole is the possibility of introducing radiation from the feedline which can make for R.F. in the Shack if not properly acconted for , it also makes predicting the radiation pattern a little skewed to the long end of the dipole. I Use two off center fed dipoles (miss nomer windoms) here one is cut for 40m long the other 20m long the 40m long one is fed with a 4:1 balun and 75 ohm coax the 20m long is fed with 300 ohm open wire line to a tuner. both antennas do a good job for me. I do mostly causual dxing (but as one poster has already said you'll have to decide which propagation mode you are seeking if grayline put up a vertical or other lowangle radiator for 80meters.) They are mounted at 90 degrees to each other. I've been able to work lots of dx on these antennas .. I had two g5rv's up prior to these and from a pure operational veiw point find them a little better at my location. hope this is of some help. 73 Dave |
#4
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"KC1DI" wrote in message ... Thierry wrote: Thanks for all comments. ... I Use two off center fed dipoles (miss nomer windoms) here one is cut for 40m long the other 20m long the 40m long one is fed with a 4:1 balun and 75 ohm coax the 20m long is fed with 300 ohm open wire line to a tuner. both antennas do a good job for me. I do mostly causual dxing (but as one poster has already said you'll have to decide which propagation mode you are seeking if grayline put up a vertical or other lowangle radiator for 80meters.) They are mounted at 90 degrees to each other. I've been able to work lots of dx on these antennas .. I had two g5rv's up prior to these and from a pure operational veiw point find them a little better at my location. For sure the location add a bias factor, soil, rock, sand, trees, etc affect the radiation pattern, all the more that on my Windom the coax segment will be at 50% in trees... although the ladder line of my G5RV was in the air, off trees... Anyway, I will have the confirmation in a few weeks. If results are "unattended" I will post a new msg. 73 Thierry, ON4SKY hope this is of some help. 73 Dave |
#5
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The original windom of the 1920's had a single wire (vertical)
feedline. The Carolina Windom as sold by Radioworks has RF radiation from the feedline which is a deliberate design consideration of this antenna; it has a vertical element (the piece of coax hanging off the balun) which is designed to radiate,. and which creates the low angle lobes. The RF radiation is STOPPED at the RF choke which is at the end of the "feedline". Then YOU feedline connects here and essentially does not radiate. There is alot of information on this antenna at http://www.radioworks.com/, some of which contradicts some of the mythology which appears in the NG's and reflectors.. 73 Dan (k0dan) Hi Thierry: The only draw back of the off center fed dipole is the possibility of introducing radiation from the feedline which can make for R.F. in the Shack if not properly acconted for , it also makes predicting the radiation pattern a little skewed to the long end of the dipole. I Use two off center fed dipoles (miss nomer windoms) here one is cut for 40m long the other 20m long the 40m long one is fed with a 4:1 balun and 75 ohm coax the 20m long is fed with 300 ohm open wire line to a tuner. both antennas do a good job for me. I do mostly causual dxing (but as one poster has already said you'll have to decide which propagation mode you are seeking if grayline put up a vertical or other lowangle radiator for 80meters.) They are mounted at 90 degrees to each other. I've been able to work lots of dx on these antennas .. I had two g5rv's up prior to these and from a pure operational veiw point find them a little better at my location. hope this is of some help. 73 Dave |
#6
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"dmr" wrote in message ... The original windom of the 1920's had a single wire (vertical) feedline. The Carolina Windom as sold by Radioworks has RF radiation from the feedline which is a deliberate design consideration of this antenna; it has a vertical element (the piece of coax hanging off the balun) which is designed to radiate,. and which creates the low angle lobes. The RF radiation is STOPPED at the RF choke which is at the end of the "feedline". Then YOU feedline connects here and essentially does not radiate. I use a common chocke balun. the coax doesn radiates RF. Thierry There is alot of information on this antenna at http://www.radioworks.com/, some of which contradicts some of the mythology which appears in the NG's and reflectors.. 73 Dan (k0dan) Hi Thierry: The only draw back of the off center fed dipole is the possibility of introducing radiation from the feedline which can make for R.F. in the Shack if not properly acconted for , it also makes predicting the radiation pattern a little skewed to the long end of the dipole. I Use two off center fed dipoles (miss nomer windoms) here one is cut for 40m long the other 20m long the 40m long one is fed with a 4:1 balun and 75 ohm coax the 20m long is fed with 300 ohm open wire line to a tuner. both antennas do a good job for me. I do mostly causual dxing (but as one poster has already said you'll have to decide which propagation mode you are seeking if grayline put up a vertical or other lowangle radiator for 80meters.) They are mounted at 90 degrees to each other. I've been able to work lots of dx on these antennas .. I had two g5rv's up prior to these and from a pure operational veiw point find them a little better at my location. hope this is of some help. 73 Dave |
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