Building a DIY antenna for 2.4 GHz. Need to support elements and bond components together.
Are common epoxies non-absorbing at this wavelength?
Thanks,
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DaveC snipped-for-privacy@privacy.net This is an invalid return address Please reply in the news group
Put a sample into the epoxy tester in your kitchen, along with a glass of water to provide some load.
If the sample gets hot or melts, it is an absorber.
Roby
Cure some and put it in the microwave oven and see how fast it gets hot compared to an equal volume of water.
dumb idea, try some epoxy in your microwave cooker, see if it heats up. I tried it with PVC plumbing pipe when I was making some hi gain
2.4G helical antenna. the PVC didnt get warm, so it didnt adsorb uWavesmartin
"Wales is a big welsh-shaped rain collection device"
Well, if you build a yagi, there is no voltage where the elements cross the boom. It does not matter what you use there (insulator, conductor) as long as it is small.
Thomas
On Fri, 27 May 2005 00:11:16 -0700, Zak wrote (in article ):
Panel antenna driven by 4 dipoles. Standoffs and epoxy between driven elements and reflector. Any absorbing material there, I think, will effect performance.
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The first thing you have to worry about if there is any dielectric other than air between elements is how it changes the optimum element length and spacing, because of the change in the propagation speed of light.
I suspect that the solution gets quite complex. Is there some rule-of-thumb that can be used? Or possibly support the elements by the ends, minimizing the dielectric between the elements and reflector?
Thanks,
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Since most of the voltage appears at the ends of antenna elements, you want to keep supports away from the ends. It would take some test data (or simulations) to determine how placing elements, say, on the surface of a circuit board, instead of rods suspended in air would alter the resonant lengths and optimum spacings.
On Wed, 1 Jun 2005 22:07:51 -0700, THE-RFI-EMI-GUY** wrote (in article ):
I was going to ball-park it by supporting only the centers of the rods, thereby minimizing the impact of the stand-offs. The rods are really short (~
3 cm) so I'm betting that if I support only the center of each rod, they won't be impacted much.-- Please, no "Go Google this" replies. I wouldn\'t ask a question here if I hadn\'t done that already. DaveC me@privacy.net This is an invalid return address Please reply in the news group
Dave It shouldn't be too complex to estimate the element length of an antenna partially supported in a dielectric.
An eng>>>Panel antenna driven by 4 dipoles. Standoffs and epoxy between driven
--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"
The Lost Deep Thoughts By: Jack Handey
Before a mad scientist goes mad, there\'s probably a time
when he\'s only partially mad. And this is the time when he\'s
going to throw his best parties.
Dave It shouldn't be too complex to estimate the element length of an antenna partially supported in a dielectric.
An eng>>>Panel antenna driven by 4 dipoles. Standoffs and epoxy between driven
--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"
The Lost Deep Thoughts By: Jack Handey
Before a mad scientist goes mad, there\'s probably a time
when he\'s only partially mad. And this is the time when he\'s
going to throw his best parties.
Just got into this thread, but checked back along it to the original question.
I think epoxies are not too good as UHF dielectrics. I know that standard "green" epoxy-glass circuit board material is not. You might try "hot-melt" adhesive, especially the milky-clear ones. They are likely to be polyethylene or a related compound. Polyethylene is used as the dielectric in many types of coaxial cable, and is pretty decent even at UHF.
Isaac
Well the shorter they are (IE: UHF/Microwave antenna) the more significant effect the dielectric support is going to have on the overall electrical length. What frequency is this antenna?
Joe
DaveC wrote:
--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"
The Lost Deep Thoughts By: Jack Handey
Before a mad scientist goes mad, there\'s probably a time
when he\'s only partially mad. And this is the time when he\'s
going to throw his best parties.
On Wed, 1 Jun 2005 22:07:51 -0700, THE-RFI-EMI-GUY** wrote (in article ):
That's easy; measure.
OK, that seems logical.
How did you determine how much to trim? By the same percentage that the rods were supported by the yoke?
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On Fri, 3 Jun 2005 21:36:17 -0700, THE-RFI-EMI-GUY** wrote (in article ):
2442 MHz, center f. 802.11 wlan.-- Please, no "Go Google this" replies. I wouldn't ask a question here if I hadn't done that already.
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