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4nec2 simulation of a pvc sheet?
I have successfully constructed various 2400 Mhz antennas using the
4nec2 antenna modelling software (really great application, warm tnx to the author should he read this!) What I would like now is to get a rough idea as to how close I can put the antenna elements to a PVC casing without disturbing the radiation pattern, SWR etc. E.g. by putting a 2 mm lossless PVC sheet (with dielectricity constant = 7) 1 cm in front of the antenna element. Is it possible to simulate this? Alex |
I have successfully constructed various 2400 Mhz antennas using the
4nec2 antenna modelling software (really great application, warm tnx to the author should he read this!) What I would like now is to get a rough idea as to how close I can put the antenna elements to a PVC casing without disturbing the radiation pattern, SWR etc. E.g. by putting a 2 mm lossless PVC sheet (with dielectricity constant = 7) 1 cm in front of the antenna element. Is it possible to simulate this? Alex Not with a freebie NEC based program. Also, Why are you using PVC? This stuff is horrible as a base substrate at 2.4 GHz. 73, Chip N1IR |
Who told you PVC was lossless? Stick a sample of it in a (2.4 GHz) microwave oven and see what happens. You could
simulate it with a sheet of carbon impregnated foam, but I guess 4nec2 doesn't handle that either. If you need a radome, use foam polystyrene, commonly known as Styrofoam®. -- Crazy George Remove N O and S P A M imbedded in return address "Alex" wrote in message ... I have successfully constructed various 2400 Mhz antennas using the 4nec2 antenna modelling software (really great application, warm tnx to the author should he read this!) What I would like now is to get a rough idea as to how close I can put the antenna elements to a PVC casing without disturbing the radiation pattern, SWR etc. E.g. by putting a 2 mm lossless PVC sheet (with dielectricity constant = 7) 1 cm in front of the antenna element. Is it possible to simulate this? Alex |
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On Tue, 14 Sep 2004 10:23:18 -0500, "Crazy George"
wrote: Who told you PVC was lossless? Stick a sample of it in a (2.4 GHz) microwave oven and see what happens. You could simulate it with a sheet of carbon impregnated foam, but I guess 4nec2 doesn't handle that either. If you need a radome, use foam polystyrene, commonly known as Styrofoam®. many tnx for your answer actually I am using styrofoam already for the indoor model. But styrofoam is too soft and vulnerable to make weatherproof so I shall have to put it in a case made of something more rugged. Evidently 4nec2 does not handle the needed simulation so I shall look around for other software or maybe make a SWR meter and some practical experiments... Alex |
PVC is not lossless, however...
I used PVC drainage pipe (white, 3 mm thick maybe) to make radome for 900MHz antenna. Specifically, directional patch arrays. It tuned them down a little bit (2 mm maybe over half-wave length.) I did not measure significant decrease of gain. The cover did not touch the radiator. When it touches, loading get significantly worse. Andrey It"Alex" wrote in message ... On Tue, 14 Sep 2004 10:23:18 -0500, "Crazy George" wrote: Who told you PVC was lossless? Stick a sample of it in a (2.4 GHz) microwave oven and see what happens. You could simulate it with a sheet of carbon impregnated foam, but I guess 4nec2 doesn't handle that either. If you need a radome, use foam polystyrene, commonly known as Styrofoam®. many tnx for your answer actually I am using styrofoam already for the indoor model. But styrofoam is too soft and vulnerable to make weatherproof so I shall have to put it in a case made of something more rugged. Evidently 4nec2 does not handle the needed simulation so I shall look around for other software or maybe make a SWR meter and some practical experiments... Alex |
On Tue, 14 Sep 2004 11:31:29 -0700, "Andrey"
wrote: PVC is not lossless, however... I used PVC drainage pipe (white, 3 mm thick maybe) to make radome for 900MHz antenna. Specifically, directional patch arrays. It tuned them down a little bit (2 mm maybe over half-wave length.) I did not measure significant decrease of gain. The cover did not touch the radiator. When it touches, loading get significantly worse. tnx for your reply But it seems to me that what you describe is not so much that the PVC absorbs energy ("loss") but instead: that it unavoidably de-tunes the antenna because of its high dielectric constant (about 5 to 9 I understand). Especially when the PVC touches the radiators the capacitance between radiator parts is markedly reduced because of this phenomenon (anyway that is how I intuitively understand it...) Alex |
But it seems to me that what you describe is not so much that the PVC absorbs energy ("loss") but instead: that it unavoidably de-tunes the antenna because of its high dielectric constant PVC is L-O-S-S-Y at 2.4 GHz. The amount varies according to manufacturer. CPVC has the least loss of a lossy lot. OK?:-) 73, Chip N1IR |
"Alex" wrote in message ... On 14 Sep 2004 12:38:36 GMT, (Fractenna) wrote: Also, Why are you using PVC? This stuff is horrible as a base substrate at 2.4 GHz. Because I can get a cheap PVC case which is otherwise suitabel for weatherproofing the antenna. And because I have seen reported (I have not tried it myself) that such material does not get heated in a microwave oven. You should try this yourself. I think you will be surprised. |
Because I can get a cheap PVC case which is otherwise suitabel for
weatherproofing the antenna. And because I have seen reported (I have not tried it myself) that such material does not get heated in a microwave oven. This is a good, first-order test. But, as warned, different pvc manu's give different results. It wasn't made for s-band RF. You must test it thoroughly without extrapolating. Some is almost OK; others are really poor. Sure ain't kidex. 73, Chip N1IR |
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