Xmit loop antenna for all bands.Dbl helix cont"d

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KB9MZ, Nov 21, 2009.

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  1. KB9MZ

    KB9MZ Ham Member QRZ Page

    If one is going to make a really, really small anyenna, say for the attic
    I would bear in mind that wireing e.t.c. could affect the antenna.
    As Kraus states with his helix antenna you should have at least 2 to 7 WL
    of wire in the construction. The reason being as the number of WL increase
    the amplitude of the the SWR sine wave begins to dampen out and if you use enough WL one could obtain a near flat line in SWR in terms of frequency response.
    You can now see why mesh fits well as a antenna as it automatically has stacked in many WL in its structure so SWR is pretty well dampened out.
    Now for those who which to put one in the attic one should be aware that other object can affect the damping spoken of. To combat this possibility one can split one side of the mesh and add a aluminum plate to the severed ends.
    This way you have an alternative method of tuning as the plates form a capacitor. When doing this it is important to ensure that the mesh overlaps such that the screening action is still observed. If you don't have a problem then it is easier to screw the plates together without having to extract it from the attic.
    I believe that Moxon's dream of a antenna design for small gardens have come about and I will see more "G" stations on the band. But RADCOM
    will never make it available to all.
    Cheers
     
  2. K4SAV

    K4SAV Ham Member QRZ Page

    I am convinced Art has a problem, but I don't think he exhibits this behavior out of any intent to be mean, boost his own ego, or perform the function of a troll. If you knew Art's background you would understand.

    Keep trying Art. I am sorry I was not able to lead you down that path to "connect the dots".

    Jerry, K4SAV
     
  3. KB9MZ

    KB9MZ Ham Member QRZ Page

    That's OK Jerry, you kept on subject as much as you could, whereas others
    feel there is no need for logic and try to drown out with insults. Frankly, there is to much of the latter as the cross section of ham types begins to erode
    Science books state that radio and propagation is not fully understood! Yet many hams will not even consider the idea of change. Especially as the group gets older and hams begin to expand in their perceived knowledge as to what is really correct while hiding behind a mike. It is much safer than debating in person where one can is considered a silly old fool. Yes, one can start a conversation as to how things were handled in the "old days" but it never lasts for long as the company soon disapears!
    Regards
    Art
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Let's hear it on the air. I have lots of antennas that match coax perfectly and provide a 1:1 VSWR. Many of them could not make a contact with anybody. Some of them could.

    My very best antennas are quite narrow banded and might have a VSWR that's fairly low at some frequency, but continue to work well and make thousands of contacts off resonance when the SWR is 10:1.

    Let's hear it on the air.
     
  5. K4SAV

    K4SAV Ham Member QRZ Page

    I'm not sure if Art operates anymore (from one of his old posts), but he can confirm or deny that. If he does, you need to first confirm WHAT the antenna actually is. That "mesh" antenna turned out to be a vertical monopole because of the way it was implemented. We didn't get any details on the window screen antenna, although "lying on the lawn" it's not likely to radiate much signal.

    Jerry, K4SAV
     
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Making measurements on impedance matching tell us nothing about the antenna's ability to actually radiate.

    Making contacts on the air might.

    Making measurements on a range, or in an anechoic chamber with a calibrated reference antenna might.

    I have hundreds of theoretical antennas that can't make any contacts but otherwise provide many benefits.

    The TAK-tenna, the E-H, the Isotron...which all rely on feedline radiation are pretty good examples.

    If someone presented a paper at a symposium on electromagnetics describing an antenna that did a bunch of stuff in theory but had never built a working model that provided empirical results, he'd be laughed out of the room.
     
  7. KA5S

    KA5S Ham Member QRZ Page

    Sounds like the Antennas and Propagation Society. Except they often DO build models to test simulations, and report the results too, even when not as close to reality as was hoped.


    Cortland
    KA5S
     
  8. G7VQE

    G7VQE Ham Member QRZ Page

  9. KB9MZ

    KB9MZ Ham Member QRZ Page

    Let me review this antenna so we can have a dialog between the antenna and the Cross Field Antenna. Hopefully there is somebody out there is knowlegable about the CFA concept. How I understand it the CFA concept is based on the premise of two fields in existence (E&H) without the presence of current.
    Well we all know, or think we know, that something went wrong and the transmission line became the radiator.

    Now consider a Faraday shield that has an electric field on the outside and a magnetic field on the inside (The faraday shield has the ability to separate the fields). Now both fields basically consists of electrons or small particles.
    The shield is basically an arbitrary field just like the one explained in the Gauss law of statics. We can see these particle vectors spread around the inside of the boundary facing outwards. On the outside of the arbitrary border or Faraday shield we also have a series of vectors from the particles formed by the electrical field. When these appear on the outside of the
    Faraday shield the particles inside immediately reposition them selves as opposing( now in phase) the outside vectors according to Newtons laws. When these vectors are equal and opposite, which means in a state of equilibrium, there is no current flowing which is the concept that the CFA inventors was pursuing but in a different and unsuccessfull approach.
    Is there anybody familiar with the CFA concept and is the Faraday shield
    performing what others have been trying to do with respect to efficient small volume antennas that are most sought over? Is there anybody out there that
    has the background to discuss such a matter without taking on an insulting aproach of a spammer? Judging by the number of viewers there seem to be considerable interest in the subject, but none willing or capable to add to the subject to satisfy the numbers of hams obviously showing interest. Now I have made small antennas for the Top Band which are rotatable using the Faraday shield method, so the question should not be shifted aside by the amateur world because of the small numbers of naysayers when all others are searching for such an antenna.
     
  10. KB9MZ

    KB9MZ Ham Member QRZ Page

    Since nobody is willing to come forward to debate I will present a mythical question !
    Your design appears to be a loop antenna but it doesn't have a gap! What happened?
    First, one can read up on a Faraday shield and it would appear that they are one and the same thing. So I accept that there is a reason for the gap in present day designs that I will leave others to look up and check for the old wives tails.
    In my design we have the electric field on the outside of the shield and the magnetic field on the inside of the Faraday shield. Actually, we are looking at particles or electrons at rest. If we draw a circular boundary with vectors representing the particles the vectors will not be exactly opposite to each other because of the phase difference. For equilibrium, as in Newtons law, the particle vectors MUST oppose each other, thus the magnetic electrons are forced to move to oppose the outside vectors . Of course when the electrons move on the inside an electric current is formed which needs to be fed to ground. To do this, radials are positioned around the inside of the shield to a common ground point in the centre of the shield to maintain equilibrium or balance. Remember, in my design ,the outside of the Faraday shield IS THE RADIATOR If one doesn't set up a common ground rest assured that the feed line will radiate. This is because for maximum efficiency in radiation one cannot leave a active lumped load in the circuit which is the reason why radials are inserted to cancel any capacitance created by the internal shield sides.
    Side note: radiation is created by particles NOT waves.
    See quantum physics !
    Happy thanksgiving day
    Art KB9MZ.....xg
     
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