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Delta Loop Ideas Please
I have been researching for a while now around the area of nested delta
loops. I want to upgrade my multi-band vertical antenna with delta loops, each one resonant to cover 20 to 10m. However there is nothing on the internet about nested delta loops. My wish is to have the delta loops orientated such that they are pointed at the top and fed one third of the way up one of the vertical sides to get a low angle of radiation. I realise that they have an impedance of around 100 Ohms and this would need to be matched. The usual method of doing this is to use a quarter wave length of 75R coax to match to 50R. Much in the same way that parallel dipoles can be fed with a common feeder, can 5 delta loops be fed via coax matching stubs with a common 50R feeder? (i.e. bring the ends of the matching stubs together?). I tried in the summer to nest 5 delta loops with the feed point as described above and then brought the feed points together (without matching stubs) , however it is not physically possible to do this - they really need separating out. Any ideas any one? My basic aim is to have 5 resonant antennas with no tuning unit involved. Thanks John |
Delta Loop Ideas Please
Can it be done, - yes...
Will it work well - maybe! You are going to have mutual coupling between the loops messing up resonance and impedence... You cannot just cut the loops per the formula and nest them inside of each other, connected at the feed point, and still be resonant... That is your first problem... Search the literature on triband quad loop beams and their results will point the way to the appropriate modification of the usual loop formula... Next, your impedences will drop and 100 ohms is not likely to be the number... For a single feedline try a quarter wave of twin lead from the mutual feed point to each respective loop... Personally, I would use relays to cut out the unused loops and save myself a lot of cut and try... ymmv... 15 -17 will talk to each other... Try hanging them at right angles... denny / k8do John wrote: I have been researching for a while now around the area of nested delta loops. I want to upgrade my multi-band vertical antenna with delta loops, each one resonant to cover 20 to 10m. However there is nothing on the internet about nested delta loops. My wish is to have the delta loops orientated such that they are pointed at the top and fed one third of the way up one of the vertical sides to get a low angle of radiation. I realise that they have an impedance of around 100 Ohms and this would need to be matched. The usual method of doing this is to use a quarter wave length of 75R coax to match to 50R. Much in the same way that parallel dipoles can be fed with a common feeder, can 5 delta loops be fed via coax matching stubs with a common 50R feeder? (i.e. bring the ends of the matching stubs together?). I tried in the summer to nest 5 delta loops with the feed point as described above and then brought the feed points together (without matching stubs) , however it is not physically possible to do this - they really need separating out. Any ideas any one? My basic aim is to have 5 resonant antennas with no tuning unit involved. Thanks John |
Delta Loop Ideas Please
On Fri, 29 Dec 2006 10:35:40 -0000, "John" wrote:
I tried in the summer to nest 5 delta loops with the feed point as described above and then brought the feed points together (without matching stubs) , Hi John, Without matching (stubs? these are usually shorted or open - perhaps you mean lines) seems to go against your goal of a 5 band, no-tune antenna. The alternative is to have 5 matching lines, a lot of wire in the air. however it is not physically possible to do this - they really need separating out. It would seem to be physically possible, just not elegant, nor successful. If you are willing to invest in such complexity and wire, why not ONE antenna that does it all without such grief? Consult: http://home.comcast.net/~kb7qhc/ante.../Cage/cage.htm or http://www.qsl.net/kb7qhc/antenna/Discone/discone.htm 73's Richard Clark, KB7QHC |
Delta Loop Ideas Please
Much in the same way that parallel dipoles can be fed with a common feeder,
can 5 delta loops be fed via coax matching stubs with a common 50R feeder? (i.e. bring the ends of the matching stubs together?). Not necessarily no, but I think it will give you a headache. If you don't have antenna modeling software on your side, you're going to have to do it experimentally and you're probably not going to get much help on the internet. You might consider going with full-wave rectangles that are twice as high as they are wide. They don't need any matching stubs; they're 50 ohms to start with. There will be big interaction among any 5-HF-band loops at any rate. You might do better with switching all five feedlines with a remote coax switch of some description. 73, Dan |
Delta Loop Ideas Please
A full wave 20 meter delta loop, fed with open wire, ladder line or
even TV twin lead & a tuner will load up on all bands 10-40 meters. Performance on 10-20 will be good, 30 & 40 a little less so. Terry W8EJO John wrote: I have been researching for a while now around the area of nested delta loops. I want to upgrade my multi-band vertical antenna with delta loops, each one resonant to cover 20 to 10m. However there is nothing on the internet about nested delta loops. My wish is to have the delta loops orientated such that they are pointed at the top and fed one third of the way up one of the vertical sides to get a low angle of radiation. I realise that they have an impedance of around 100 Ohms and this would need to be matched. The usual method of doing this is to use a quarter wave length of 75R coax to match to 50R. Much in the same way that parallel dipoles can be fed with a common feeder, can 5 delta loops be fed via coax matching stubs with a common 50R feeder? (i.e. bring the ends of the matching stubs together?). I tried in the summer to nest 5 delta loops with the feed point as described above and then brought the feed points together (without matching stubs) , however it is not physically possible to do this - they really need separating out. Any ideas any one? My basic aim is to have 5 resonant antennas with no tuning unit involved. Thanks John |
Delta Loop Ideas Please
A full wave 20 meter delta loop, fed with open wire, ladder line or
even TV twin lead & a tuner will load up on all bands 10-40 meters. Performance on 10-20 will be good, 30 & 40 a little less so. Terry W8EJO John wrote: I have been researching for a while now around the area of nested delta loops. I want to upgrade my multi-band vertical antenna with delta loops, each one resonant to cover 20 to 10m. However there is nothing on the internet about nested delta loops. My wish is to have the delta loops orientated such that they are pointed at the top and fed one third of the way up one of the vertical sides to get a low angle of radiation. I realise that they have an impedance of around 100 Ohms and this would need to be matched. The usual method of doing this is to use a quarter wave length of 75R coax to match to 50R. Much in the same way that parallel dipoles can be fed with a common feeder, can 5 delta loops be fed via coax matching stubs with a common 50R feeder? (i.e. bring the ends of the matching stubs together?). I tried in the summer to nest 5 delta loops with the feed point as described above and then brought the feed points together (without matching stubs) , however it is not physically possible to do this - they really need separating out. Any ideas any one? My basic aim is to have 5 resonant antennas with no tuning unit involved. Thanks John |
Delta Loop Ideas Please
A full wave 20 meter delta loop, fed with open wire, ladder line or
even TV twin lead & a tuner will load up on all bands 10-40 meters. Performance on 10-20 will be good, 30 & 40 a little less so. Terry W8EJO John wrote: I have been researching for a while now around the area of nested delta loops. I want to upgrade my multi-band vertical antenna with delta loops, each one resonant to cover 20 to 10m. However there is nothing on the internet about nested delta loops. My wish is to have the delta loops orientated such that they are pointed at the top and fed one third of the way up one of the vertical sides to get a low angle of radiation. I realise that they have an impedance of around 100 Ohms and this would need to be matched. The usual method of doing this is to use a quarter wave length of 75R coax to match to 50R. Much in the same way that parallel dipoles can be fed with a common feeder, can 5 delta loops be fed via coax matching stubs with a common 50R feeder? (i.e. bring the ends of the matching stubs together?). I tried in the summer to nest 5 delta loops with the feed point as described above and then brought the feed points together (without matching stubs) , however it is not physically possible to do this - they really need separating out. Any ideas any one? My basic aim is to have 5 resonant antennas with no tuning unit involved. Thanks John |
Delta Loop Ideas Please
NomadW8 wrote:
A full wave 20 meter delta loop, fed with open wire, ladder line or even TV twin lead & a tuner will load up on all bands 10-40 meters. Performance on 10-20 will be good, 30 & 40 a little less so. EZNEC says the feedpoint of a 20m loop will be about 3000-j13000 on 40m. The SWR on the ladder-line line will be around 130:1. For better performance on 40m, install an insulator opposite the feedpoint thus turning it into a dipole of sorts on 40m. Short across the insulator for 20m operation. -- 73, Cecil http://www.w5dxp.com |
Delta Loop Ideas Please
Or a 1/4 wave 40 meter stub (aka wave trap/auto switch).
Cecil Moore wrote:1. For better performance, on 40m, install an insulator opposite the feedpoint thus turning it into a dipole of sorts on 40m. Short across the insulator for 20m operation. -- 73, Cecil http://www.w5dxp.com |
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