9

It depends on the frequency range the termination is rated for, and the power handling required. High power and high frequency is very difficult. At HF, any old non-inductive 50 Ω resistor will do. For higher power, we'd put many resistors in series and parallel, perhaps on a heat sink or in a can of oil. At VHF and UHF I've made very good terminations ...


9

A parabolic reflector reverses the sense of circular polarization. so your feed must have the opposite sense or "handedness" to the incoming signal to avoid significant polarization loss.


8

I haven't built one of these myself, but one of the best resources I know of for the theory is antenna-theory. The second page mostly discusses gain. There it talks about optimizing the distance between the feed antenna and the dish, given a fixed pattern for the feed antenna, but basically the same thing applies to narrowing or widening the pattern of the ...


4

Given the large physical aperture of the passive reflector, I would say this presents an excellent opportunity for ESE bounces at VHF and UHF frequencies provided they maintain proper orientation of the reflector. If the reflecting material is very thin aluminum as you suggest, there will be some loss within the reflector but not significant enough to usurp ...


4

According to Wikipedia for IRLP: IRLP connections are of two types: node to node, and node to reflector. Stations wishing to communicate with 3 or more nodes at the same time may accomplish this by connecting to what is called an IRLP Reflector. Reflectors are a type of conferencing system. Most reflectors on the network have 10 channels (0-9) with ...


3

If the only thing the material did was "reflect", and it was like a flag on a vertical antenna, then I guess it wouldn't have any effect on the radiation pattern. The problem is that no such material exists. One problem is that for a material to "reflect", it has to be many (at least 10, say) wavelengths long. Any less than this, and effects like ...


2

The information on Dish illumination is Correct. That is... the Angle of the waves from the Dish to the Feed Antenna ( helical ) at the Widest (rim) point. Using an off-center point feed makes it Vary Hard to design. the next thing is the Focal Point. this is the Exact Point the Waves are Concentrated at, to set the Helical at. It is like taking a ...


2

If the transmitted signal induces any currents in the "sheet", the sheet will affect the radiation pattern. One simple argument: if you run a wire parallel to the "flag pole", there will be induced currents. They may be small (if the wire is not resonant) but there will be some current. (Think of how a yagi antenna works with its "parasitic" elements.) ...


1

Much depends on the relative sizes. A metal flag on an HF vertical antenna is not likely to change the pattern in any way you'd notice. A gum wrapper near a 2.4GHz antenna definitely will change the pattern. I once did a design for a 2.4Ghz consumer product and ended up sculpting the antenna pattern with a block of nylon adjacent to the antenna, acting ...


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