| Electronics > Projects, Designs, and Technical Stuff |
| Radome construction |
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| coppercone2:
I would pour tar around it but its not very appealing now that I think about it, it will look like a pimple |
| German_EE:
I should point out that the roof holding my home made radome and the satellite dish was flat and everything was well secured. Yes, it could have blown off in severe winds but it is more likely that the polythene would be ripped away leaving the wooden frame. Actual radomes for radar are much more interesting as they need to avoid heating from the high RF output yet remain RF transparent for reception. In the past I have tested RF construction materials in the microwave, if they warm up after a quick blast then they don't get used. |
| TheUnnamedNewbie:
There are two real ways to build radomes: Either you build them as thin as you can, with low dielectric constant materials. This way, you can hope your radome will simply be 'invisible' to passing waves. The trick, to my knowledge, used on aircraft is to not do that at all. Instead, you design your radome to be a 'matching' network, in such a way that the plane wave passing through it at the angle you expect sees 1/4 wavelength of material (that being, of course, 1/4 wavelength given the dielectric constant of the material, no free-space wavelength). If you do this, you can't just replace one radome with a random other radome - they are designed with specific frequencies and phase centers in mind. The designers will also specify a very specific thickness, and making it thinner (even if you could, strength-wise) would hurt performance. Interestingly, there is some research into applying these techniques to bumpers of cars, to integrate the radar modules in a neater way. This adds a requirement to the material properties - you need them to be predictable and repeatable. |
| coppercone2:
is the radome at a far field distance from the antenna in this case? |
| coppice:
--- Quote from: German_EE on October 09, 2019, 05:09:46 pm ---I should point out that the roof holding my home made radome and the satellite dish was flat and everything was well secured. Yes, it could have blown off in severe winds but it is more likely that the polythene would be ripped away leaving the wooden frame. Actual radomes for radar are much more interesting as they need to avoid heating from the high RF output yet remain RF transparent for reception. In the past I have tested RF construction materials in the microwave, if they warm up after a quick blast then they don't get used. --- End quote --- An issue with radomes on the nose of aircraft is the need to have a metal strap across the fibre glass dome for lightning protection, without the strap reflecting too much power back into the receiver, especially when using a continuous transmission type of radar, like FMICW. |
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