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14888Re: AW: AW: [SDRSharp] ebay antenna

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  • Ken Alexander
    Jun 25, 2014
      To take things a logical step further, this forum is about one particular piece of SDR software, not hardware.  However, antennas are of interest to all radio users.  Witness the huge amount of traffic this one question generated, compared to discussions of SDRSharp.

      Sometimes, unless you're a member of multiple forums you have to ask a question where you think you're likely to get a useful reply, which might not always be the most appropriate place to ask.  There are a lot of smart people on the SDRSharp forum, so it's a good place to ask questions.

      That's why.

      73,

      Ken Alexander
      VE3HLS



      On Jun 25, 2014, at 9:13 PM, "'Alan Wheaton' alanwh@... [SDRSharp]" <SDRSharp@...> wrote:

       

      SDR,SDR,SDR,SDR,SDR, IS THIS NOT WHAT THE FORUM IS ABOUT

      WHY CARRY ON ABOUT OTHER RUBBISH

       

      Alan

       


      From: SDRSharp@... [mailto:SDRSharp@...]
      Sent: Thursday, June 26, 2014 10:35 AM
      To: SDRSharp@...
      Subject: Re: AW: AW: [SDRSharp] ebay antenna

       

       

      I won't quite call you on that one, John. An LPA has significant gain
      over a dipole in general terms. It is closer to something between a
      two and three element beam for most practical designs. The discone,
      however, generally does no better than a dipole mostly worse than a
      dipole.

      Now, that is presuming directional gain does not adversely affect your
      application. If you need an omni directional the discone is a vertical
      polarization very wide band "compromise antenna." And the LPA will not
      do the job. Define the application, learn the characteristics of the
      antennas that are available, remember you cannot get more power out of
      an antenna than you put into it (all you can do is concentrate the power
      in favored directions), and pick your antenna accordingly.

      On HF most hams think of the multi-element versions of the MonstIR up 100'
      as an "ultimate beast", especially if you have stacked versions. But, for
      some uses, such as regional rag chewing you have a different selection to
      make. Even a G5RV at a quarter wave up in the air works very well compared
      to a beam. At low heights the radiation pattern is pretty much that of an
      omni-directional cloud burner, a bubble sitting on the ground. The only
      thing you can do better for that is a full wavelength loop at just the
      right height to give a punched in bubble. It will reach out a couple dB
      worth farther. (At night on 75 meters that can mean you reach New York
      and Alaska from the So Cal/Vegas region. I've even (barely) made Hawaii
      with 100W once.)

      So it's really not practical to define a "best antenna" without the
      associated qualifiers that define what "best" might entail.

      {^_^} Joanne

      On 2014/06/25 08:50, John Ferrell jferrell13@... [SDRSharp] wrote:
      > In most cases a dipole cut for the frequency of interest will equal or
      > better perform than a discone or LP antenna.
      > Wide band antennas are a bit like a "Swiss Army Knife". They work, but
      > not nearly as well as the special purpose tool.
      > FWIW, I carry a Swiss Army knife, tiny Channel Lock pliers, and a tape
      > measure at all times.
      > I am finding SDR# with a dongle very effective on the 2 meter Ham band
      > (144-148 mhz) with an 11 element yagi at about 60 feet.
      > So far I am not happy with the sensitivity I experience around 14 mhz
      > with an upconverter and a 3 element beam at the same height.
      > The problem is NOT with SDR#!
      >
      > On 6/25/2014 4:54 AM, YT9TP Pedja yt9tp@... [SDRSharp] wrote:
      >> On 25.6.2014 5:54, MCH mch@... [SDRSharp] wrote:
      >>> Wish I could find an inexpensive LP antenna for 30-900 MHz...
      >>
      >> I guess discone or horn antenna might do.
      >

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