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70208Re: Antenna problems?

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  • vbifyz
    Nov 19, 2012
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      My tuned loop is a hula-hoop about 1m diameter with 14ga wire threaded through it. You don't have to use coax, any round wire will do. The variable capacitor is from an old radio, 2 sections about 400pF max each. I tied it with cable ties to the loop and added a switch to flip between a single section and 2 sections in parallel. The coupling loop is about 20cm diameter.
      It does not give the optimum signal level for the Softrock, but in a high noise situation such loop allows to hear many more signals than any wire contraption. The tuning range is from 3.5MHz to about 15-16MHz.
      I tried PA0RDT mini-whip as well and didn't see any noise rejecting properties compared to a random wire.

      73, Mike

      --- In softrock40@yahoogroups.com, Ulf Holt Gmail <ulf.holt@...> wrote:
      >
      > I will try this construction, but I have a few questions.
      > 1) what dimensions are we talking about?
      > 2) how large capacitor and do I have to pick a frequency on the receiver and then go back to the antenna and tune the capacitor, for the optimal signal? As it is now, I can't hear any signals at all.
      > 3) what kind of coax? The only coax I could get my hands on here is 60 ohm coax for surveillance cameras, which i had to use for feeding the receiver,but off course when I go to Bangkok later this week, I can get whatever I want. I suppose RG213 would be a possible choice. RG58 is too soft if the ring has a diameter larger 20 - 30 cm. maybe I should replace the feeder, using RG58 instead?
      >
      > Ulf
      >
      >
      >
      > Sendt fra min iPad
      >
      > Den 19. nov. 2012 kl. 04:29 skrev "junius fox" <jfox05@...>:
      >
      > > Hello, You can construct a nice receiving antenna out of coax and a inexpensive plastic variable that are used in cheap radios.
      > > the antenna is shown below:
      > >
      > >
      > > ----- Original Message -----
      > > From: Ulf Holt
      > > To: softrock40@yahoogroups.com
      > > Sent: Sunday, November 18, 2012 2:44 AM
      > > Subject: [softrock40] Antenna problems?
      > >
      > >
      > > As I have mentioned in my request for Software (I have now choosen to use PowerSDR-iq) I have problems reveiving anything. I got a Chinese AM station the other day, so I suppose the RX Ensemble II receiver is working in some way or another, but I am not very impressed of the sensivity. My problem is how to put up an antenna to test this radio.
      > >
      > > I am on a long vaccation in Thailand, and we live on second flor in a building that is 18 flors, and the only chanse for me is a balcony which is not very large and east bound. To make things even worse, both sides are shielded with concrete, so I only have an free opening that is about 1.8 m x 4 m. I tried to put up a simple wire about 4 meter long, and connected it to the inner cord of a coax, which I connected to the receiver. A really bad solution, but I still would expect to pick up something, but I cannot get anything at all. If I remove the antenna, I can heare a difference, the noise level is falling, but that's about it.
      > >
      > > Any bright ideas out there?
      > >
      > > 73 de LA2SL
      > >
      > > Ulf
      > >
      >
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