Ham Radio - The Chameleon Antennas power compensator for magnetic loops.

Discussion in 'Amateur Radio News' started by KB7TBT, Nov 3, 2019.

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  1. KR3DX

    KR3DX Ham Member QRZ Page

    It's simple. No need to spend 15 minutes watching a video. To make a small antenna as efficient as possible, you want to make the current as uniform as possible over the length of the antenna by using as much capacitance as possible at the ends of the antenna. That's all that this "power compensator" (their name for a capacitor) is doing. You want to use an antenna that is physically small compared to the wavelength only when you have no other choice. It's a little bit better than a leaky dummy load.
     
  2. PA0MHS

    PA0MHS XML Subscriber QRZ Page

    That would be true for the capacitor between the ends of a loop. This capacitor is only connected to one end of the loop and not even used as a capacitor because the other endof the capacitor is not connected to anything. So this capacitor does nothing as a capacitor. It's just a parasitic "load" on one end of the loop, thus lowering the Q. And that will also lower the current through the loop and the voltage across the tuning capacitor, allowing more power to be input to bring the radiated power to the same level as without the "power compensator". This is just a fake product, sold to make money and to make you feel good.
     
    K7LZR and VE3VXO like this.
  3. KR3DX

    KR3DX Ham Member QRZ Page

    There is no PHYSICAL connection, but the other plate of the capacitor DOES couple to the loop and affect its performance. Otherwise, I agree with you completely. W8JI has a very good explaination of "magnetic loops" on his website: https://www.w8ji.com/magnetic_receiving_loops.htm
     
  4. PA0MHS

    PA0MHS XML Subscriber QRZ Page

    That is exactly what I meant with "It's just a parasitic "load" on one end of the loop". If this device had been a metal disc, it would have had the exact same effect.
     
  5. KR3DX

    KR3DX Ham Member QRZ Page

    I agree completely
     
  6. AA6RE

    AA6RE XML Subscriber QRZ Page

    So far it looks like everyone agrees its a HV cap with one end attached to the loop on one side of the tuning cap inside the box. The other end is just left hanging in the air.

    Sure there is some stray capacitance to ground, to the loop and to the tuning cap in series with this 500pf cap. Maybe this stray is 50 pF ( just a guess). These two caps, the stray capacitance and 500pf in series give a total capacitance of 45 pF. I think the experiment would benefit from a field strength (FS) measurement made with 5 Watts and a FS measurement at the maximum power that the compensator is rated for.

    If there is a way to measure loop current that would be nice to have as a check. Both measurements would be made when tuned to match the signal source.
     
  7. KK4HPY

    KK4HPY Ham Member QRZ Page

    If you watch the video he verifies everything to be working except for far field results.
    1. The tuning cap did not arc with higher input power
    2. The addition of the cap did not reduce near field signal strength at the same input power
    3. Adding more input power with the cap resulted in higher near field signal strength.

    I would like the debunkers to explain how this thing increases near field signal strength but does not increase far field signal strength.
     
    Last edited: Nov 17, 2019
  8. KK4HPY

    KK4HPY Ham Member QRZ Page

    He measured the same field strength at the same input power with or without the extra cap.
    He measured higher field strength with higher input power and no apparent bad effects.
    I would like it explained how these results show a "parasitic load".
     
  9. PA0MHS

    PA0MHS XML Subscriber QRZ Page

    His measurement is completely unreliable because of the short distance to the antenna. His field strength meter picks up everything, including standing waves on the outside of the coax to the antenna. Measuring the E field too close to the antenna and cable means nothing. The theory of resonant circuits is quite clear and proven: lower Q means lower voltage. So if he can output more power with this "compensator" without arcing on the cap, it simply means that the Q of the resonant circuit is lower than without the compensator. The only thing that influences the Q of a resonant circuit is electric or magnetic loss. So this "compensator" must introduce some sort of loss on the resonant antenna.
    I would like to see this measurement repeated in the far field, which is for an electromagnetically short antenna, at least 2 lambda away from the antenna.
     
    AA6RE, KK4HPY, KF5FEI and 1 other person like this.
  10. KK4HPY

    KK4HPY Ham Member QRZ Page

    Sounds great , maybe we can get him to to that. He is active on YouTube and responds to his subscribers.
     
    AA6RE likes this.

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