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70211Re: [softrock40] Re: Antenna problems?

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  • cbayona
    Nov 19, 2012
      Even better is a shielded loop like suggested a few days ago, the
      noise fighting capabilities on the low bands is fantastic.

      I have one and the noise from computers and related items
      went better than S9+10dB to .5 dB, I have 8 PCs and related gear
      and live next to a very noisy mid-voltage line and they bother me not one bit.

      Mine is an untuned loop so no tuning when you change frequency but a
      tuned one has it's advantages, if helps keep other frequencies from
      overloading your SoftRock, but no signals on the panadapter.

      At 09:54 AM 11/19/2012, you wrote:
      >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
      > > >
      > >

      Cecil - k5nwa
      http://www.softrockradio.org/ http://thepartsplace.k5nwa.com/

      Never take life seriously. Nobody gets out alive anyway.
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