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  1. logbook

    Basic Antenna Question

    Additionally, you should understand that a higher gain antenna (larger dBi figure) means the antenna is more directional. If that is what you want it is better. If you want to receive from all directions you want a lower gain antenna!
  2. logbook

    Basic Antenna Question

    http://en.wikipedia.org/wiki/Antenna_gain This should answer your question.
  3. logbook

    Antenna phase center

    Of course if we were clever, we should be able to predict roughly how far to move the transmit antenna pivot point once we take one incorrect set of phase measurements. This would speed up the measurement process. Even knowing which way to move the pivot point would be a start. This should be...
  4. logbook

    Antenna phase center

    On further thought my previous suggestion was over-complicated. Leave the receive antenna stationary. Pivot the transmit antenna. You then only need a simple pivot rather than an X-Y-azimuth mount! Move (slide) the pivot point on the transmit antenna until you get a good/acceptable equi-phase...
  5. logbook

    Antenna phase center

    This is my interpretation and extrapolation of the relevant information from Kraus, Antennas, 3rd ed. The phase centre of the antenna is found by finding a equi-phase front in the far field. You would move the receiving antenna in a circle centred on the expected (geometric) phase centre of the...
  6. logbook

    Antenna phase center

    If you use the 6GHz carrier at the transmit, but also split it into the receiver LO, you get a nice phase sensitive receiver. Either move the receive antenna for a minimum or use a phase shift in the LO path to do the same thing. Now, when you move the transmit antenna, you will be able to see...
  7. logbook

    microstripes

    http://www.cst.com/Content/Products/Products.aspx and then of course there is ANSOFT HFSS etc. The differences will be speed, cost, accuracy ...
  8. logbook

    microstripes

    http://www.flomerics.com/microstripes/
  9. logbook

    base loaded whip

    According Kraus (Antennas, 3rd ed) the normal mode helical antenna has a radiation resistance of 0.6 ohms at resonance. This is probably causing your problem. Kraus suggests grounding the antenna to the ground plane and feeding in a bit further away to give a good match to the feedline. A...
  10. logbook

    base loaded whip

    Check my maths, but doesn't 315MHz give 95 cm full wave, 24 cm quarter wave? I will have to check my books to see if that is a reasonable reduction down to <6.4 cm for a helical antenna. The first thing that came to my mind was to use a top loaded monopole rather than using a base loading coil...
  11. logbook

    Near field maximum

    The problem with the near field is that the nature of the antenna then becomes critical to the field shape. I would think the field intensity heading into a parabolic antenna would at first increase as you get closer, but closer than the focal length wouldn't it go the other way?
  12. logbook

    Duplex filter for 0-100 mhz and 100mhz-6Ghz.

    Please use "which" instead of "wich". This forum is in English not text speak, and the mis-spelling is annoying. Don't use C1 in the application information for the MMIC. Your diplexer handles the input coupling. A conical inductor is ideal for your application, although they are expensive...
  13. logbook

    Duplex filter for 0-100 mhz and 100mhz-6Ghz.

    Yes that is correct. On point 3, if you run below the SRF of any of the components you have to simulate to say what the response will be. It has to be said that any imperfection will make the input VSWR worse and the transfer response less. You simulate to quantify the effect.
  14. logbook

    Duplex filter for 0-100 mhz and 100mhz-6Ghz.

    >It could very well that i have i nice crosspoint at 100 Mhz but that at for example 5.8 Ghz there is a loss of 30 dB caused by the circuit That "diplexer" is a very nice piece of software. You are modelling ideal components and so the response of the low pass arm will go to DC and the high...
  15. logbook

    isotropic radiation patter equation

    This is all a bit backwards. If you radiate 1W isotropically you get 1W spread over the sphere at all distances. That's it. You had it in your first equation for TxP, although that formula gives power flux density at a distance from the antenna (watts per metre squared).
  16. logbook

    Transmission line terminating at high impedances--suggestions?

    If you are talking about a shunt reactance of 10 ohms and a shunt resistance of 50,000 ohms that is a maximum Q (when considered as a component) of 5000. A parasitic capacitance will be a lot more lossy than that.
  17. logbook

    Transmission line terminating at high impedances--suggestions?

    The reason why 50,000 ohms impedance at 500MHz is unrealistic is because 1pF at 500MHz is 318 ohms. If the chip is unpackaged and flip chipped the lowest package capacitance would have to be of the order of 0.1pF (3180 ohms) without worry about the actual circuitry involved. A quarter wave...
  18. logbook

    Linking Antenna A to B

    The type of antenna you should be looking for as the link pair is a "Yagi". You can google on this. At 100MHz this will be rather large. A dipole is a half wavelength tip to tip. That is 1.5 metre as 100MHz. The dipole would look like a rod 1.5m long with a cut in the middle where the antenna...
  19. logbook

    Linking Antenna A to B

    Understand that this is not my specialist area; nevertheless I hope I know more about it than you! The antenna you linked to is a 2.4GHz type which is entirely unsuitable for your use. So we have separate applications. 1) A low power tight beam link to your re-broadcast area. 2) A high...
  20. logbook

    Linking Antenna A to B

    I think we are missing something here. Are you planning on using a directive antenna (A) to a receive/transmit station (B) then re-broadcasting (B*)? This 300W amplifier. Does it have really low harmonics? The transmitter is giving -60dBc, which is a really tight spec for the amplifier.

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