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"COMPACtenna" - fact or fiction?

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KK6QMS, May 27, 2017.

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  1. KC1DR

    KC1DR Subscriber QRZ Page

    What was wrong with the mount?
  2. KM6AB

    KM6AB Ham Member QRZ Page

    Yes, I expect and believe I am getting the exact same performance on transmit. Antennas are reciprocal, why would you not expect it work the same on transmit as receive?

    All my comments here have been for the tri-band 2m, 220, 440 version which I own and am satisfied with. I'm also curious about the HF/2m version but don't want to buy one just for testing.
  3. N1KSP

    N1KSP Ham Member QRZ Page

    The shield braid is not soldered to the base, rather it is resting on a section that was apparently ground away with a grind stone. The factory did not align the braid with the exposed metal completely. part was resting on paint. There were also a few tiny wires from the braid which were intermittently hitting the center conductor which was exposed... Hard to explain..
    So I disassembled it, soldered the braid, and put some solder in the ground out portion to assure a positive friction connection. I will drill and tap a small hole and actually affix the braid to the base later. It was good enough to prove it was the base. The resistance from the connector center to the threaded base varied from 3 to 5 Ohms... Afterwards it was solid at about 1.4 Ohms.
    KC1DR likes this.
  4. AH7I

    AH7I Ham Member QRZ Page

    dB referenced to what.
    dB referenced to noise will be very close to the same.
    It's how the absolute receive signal strengths compare that will predict how the antennas will compare when transmitting.
  5. KM6AB

    KM6AB Ham Member QRZ Page

    If this question was directed to me please elaborate. I explained in an earlier post I compared a COMPACtenna receive signal level to a 1/4 wave whip on the same mount, etc. I recorded precise receive levels between antennas and that would indicate the difference in gain or loss between the two antennas at my test frequencies. I don't recall stating dB referenced to anything except the measured levels between the two antennas. Where does dB referenced to noise come into the conversation? AH7I's statement "It's how the absolute receive signal strengths compare that will predict how the antennas will compare when transmitting" is basically the same thing I said.

  6. AH7I

    AH7I Ham Member QRZ Page

    But not very clearly.
    That's why I asked.
    "exact signal level" and "very precise" are not numbers.
    Every measurement needs a reference to be meaningful.

    Correct me if I am wrong. I am a nurse, not an antenna range guru.
    You mentioned reciprocity. It's my understanding that reciprocity applies to the antenna pattern. Transmitting efficiency suffers R*I^2 loss.

    73, -Bob ah7i
    Last edited: Apr 20, 2020
  7. KC6ETE

    KC6ETE Ham Member QRZ Page

    The antenna docs speak of a max duty cycle, which speaks to significant power lost either in resistance or dielectric. That power wouldn't be available to radiate.
    It should also broaden the Q, which may explain the "no tune".
    I'd be very interested to see field strength measurements at some distance, compared to a standard 1/4 wave.
    K0UO likes this.
  8. KC6ETE

    KC6ETE Ham Member QRZ Page

  9. W9XMT

    W9XMT Ham Member QRZ Page

    The accuracy of that belief also is quite dependent on the radiation patterns, polarizations, frequency, and path geometries of the antenna systems at both ends of the propagation path.
    KR3DX likes this.

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