Loading ...
Sorry, an error occurred while loading the content.

Re: Comparing my G3TXQ to a well-known magnetic loop

Expand Messages
  • k1hop
    On 80M they re both equally lousy hihi :) It all comes down to capture area, and there s just not much of it with a loop on lower frequencies, whether or not
    Message 1 of 4 , Aug 1, 2009
    • 0 Attachment
      On 80M they're both equally lousy hihi :)

      It all comes down to capture area, and there's just not much of it with a loop on lower frequencies, whether or not it is made to resonate.

      For those bands, you'd probably be better off connecting the inner and outer conductors of your hex feedline together at the rig and feeding it as an end-fed long wire antenna top loaded by all the hex wires. An antenna coupler would help lots, but might not be required simply for use as a receive antenna.

      Russ K1HOP

      --- In hex-beam@yahoogroups.com, "rkiskan" <robin_kiszka@...> wrote:
      >
      > Some time ago I built a G3TXQ hex. I still have it up and running without any problems from 20-10m (5 bander). Today I got hold of a good AMA Magnetic loop antenna, this covers 80-20m, which seemed quite a good option to get 30, 40 and 80m coverage. It is 1.3m in diameter.
      >
      > I put the loop up at about 20 feet, that is about half the height of the hex. I did some comparisons and this is what I found:
      >
      > 20m - the hex wins hands down. I hear most of the signals on the mag loop, but the mag loop is noisy in comparison.
      > 40m - rcv is the same, even when the loop is resonant, I hear the same on both antenna. The difference is of course SWR, I get full power out on the loop and the hex cannot tune for that band.
      > 80m - the same as for 40m.
      >
      > So does this means the hex also is a good rcv antenna for the bands it is not built for, or is the loop just plain lousy?
      >
      > 73
      > Robin
      > OZ6ABM/5P5R
      >
    • Steve
      Russ, I hope you don t mind me correcting a possible misconception - capture area has almost nothing to do with the physical size of a typical HF antenna. By
      Message 2 of 4 , Aug 1, 2009
      • 0 Attachment
        Russ,

        I hope you don't mind me correcting a possible misconception - capture area has almost nothing to do with the physical size of a typical HF antenna.

        By way of example, at 14MHz the capture area (or Effective Aperture) of a 33ft half-wave dipole is about 640 sq ft compared to 590 sq ft for a dipole just 1ft long - that's only 8% more; in other words they "intercept" pretty much the same amount of incident power.

        The problem with very small antennas is not their capture area - its how to match efficiently the very low Rrad which they have. If you could match efficiently to a small magnetic loop, it would deliver almost exactly the same received power as a half-wave dipole at the same height.

        73,
        Steve G3TXQ


        --- In hex-beam@yahoogroups.com, "k1hop" <k1hop@...> wrote:
        >
        > On 80M they're both equally lousy hihi :)
        >
        > It all comes down to capture area, and there's just not much of it with a loop on lower frequencies, whether or not it is made to resonate.
        >
        > For those bands, you'd probably be better off connecting the inner and outer conductors of your hex feedline together at the rig and feeding it as an end-fed long wire antenna top loaded by all the hex wires. An antenna coupler would help lots, but might not be required simply for use as a receive antenna.
        >
        > Russ K1HOP
        >
      Your message has been successfully submitted and would be delivered to recipients shortly.