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  1. ojniemin

    Simulations on digital modulation

    Does anybody have an idea which would be the best tool to simulate the performance of different digital modulation types? BR, ojniemin
  2. ojniemin

    balanced/unbalanced

    I am sorry I wasn't clear enough. I am not looking for certain formulas to calculate the transmission line parameters. Rather I am looking for a primer on definition of balanced/unbalanced, baluns etc. I have a pile of book about RF but none of them really goes deeply into this. Maybe someone...
  3. ojniemin

    balanced/unbalanced

    Does anyone of you know a good primer/introduction on balanced/unbalanced transmission lines?
  4. ojniemin

    dielectric antenna

    Antenna size can be reduced by loading the antenna with dielectric material. Because the wavelenght is shorter in the dielectric the size of the antenna can be made smaller for a certain electrical size. What happens with directivity and gain? Is the radiation efficiency changed? What about...
  5. ojniemin

    Radio Controlled Switch

    Thanks DRWeig! Sure your approach is the easiest, fastest and maybe the cheapest but I would actually like to start from the scratch. Anybody knows schematics...?
  6. ojniemin

    Radio Controlled Switch

    Anyone has experience of radio controlled switches? I intend to design a circuit able to switch on/off 230V equipment remotely (mainly thinking of turning on the sauna without taking those 100 steps needed). Any good schematics on the web? This should work up to 100m free space. What about the...
  7. ojniemin

    Effective permittivity

    To pcss. As far as conductivity is concerned you might be right. What comes to d, e1, e2 I still say that they affect the resonance frequency of the antenna. You see this practically just putting your hand on an antenna tuned for 900 MHz, for example, and looking at the resonance. The resonance...
  8. ojniemin

    Free PCB software

    Thanks for the answers! I think Eagle seems to be at least OK. It is good to be free.
  9. ojniemin

    Free PCB software

    Hi, does anyone know a good, easy to use, free software for creating 2-layer PCBs for hobby purposes?
  10. ojniemin

    Effective permittivity

    Suppose you place an antenna at x=-d in material with permittivity e1. At x=0 the permittivity changes to e2 while the space is homogenious in y- and z-direction. In material with permittivity (relative) e>1 the wavelenght is shorter than in free space causing the resonance of an fixed size...
  11. ojniemin

    Lossy antenna in reception

    If the radiation efficiency of a receiving antenna is poor or the antenna has to be loaded in order to get enough bandwidth, how does this affect the noise figure of the receiving system? As an example we can take an electrically small antenna which usually have narrow bandwidth. To increase...
  12. ojniemin

    Electrically small antennas for 433 MHz

    Could anyone give me a hint on electrically small antennas for 433 MHz? The antenna shouldn't be larger than about 30mm in diameter and it will be placed close to a ground plane (1mm). I know that the antenna performance will be extremely poor but maybe some solutions are better than the others...
  13. ojniemin

    Sensor for air pressure - barometer

    Has anyone an idea where I could find an air pressure sensor that could be connected to my home alarm (if the pressure changes it means that a door or a window is opened)?Instructions to build one?
  14. ojniemin

    Traveling Wave Combiner

    Could you tell more exact what you want? How much loss can you tolerate? Bandwidth? Etc.
  15. ojniemin

    Fresnel coefficients

    Even though the transmission coefficient is higher than unity for cases when e1>e2, the power that goes trough the interface can not be more than the power of the incident wave. If the electric field component of the transmitted wave is bigger than that of the incident wave then the opposite is...

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