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Re: How long horizontal wire do i need for a 1/2wave AM Di-Pole.. where do i g

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  • Greg W:-)
    I agree with that 100% :-D heheh gW:-)
    Message 1 of 20 , Nov 11, 2006
      I agree with that 100% :-D heheh

      gW:-)

      ======================================================================


      --- In loopantennas@yahoogroups.com, John Popelish <jpopelish@...> wrote:

      >
      > I would expect excellent reception of both AM band radio
      > transmissions and lightning.
      >
    • Greg W:-)
      Ahh ,,but the built in safety fuse will trip during a lighnting or severe static event . Unfortunately that fuse is the radio :-) gregW:-)
      Message 2 of 20 , Nov 11, 2006
        Ahh ,,but the built in safety fuse will trip during a lighnting or
        severe static event .

        Unfortunately that fuse is the radio :-)

        gregW:-)

        http://www.swdxer.co.nr/

        ====================================================================


        --- In loopantennas@yahoogroups.com, QRP_1@... wrote:
        >
        >
        > I would expect excellent reception of both AM band radio
        > transmissions and lightning. [snip]
        >
        > Be careful on a cold windy day too, static electricity can build up
        > enough on that wire to knock you on your butt and can damage the radio.
        > If you use it, connect a 250 mH choke from the wire to ground to bleed
        > off any static charges.
        >
        > Rick McKee - KC8AON - Southern Ohio
        > http://www.angelfire.com/electronic2/qrp
        > http://www.angelfire.com/electronic2/qrp/forsale.html
        > Monthly QRP Field Day Group: http://groups.yahoo.com/group/mqfd
        > With God all things are possible <><
        >
      • QRP_1@juno.com
        Ahh ,,but the built in safety fuse will trip during a lighnting or severe static event . Unfortunately that fuse is the radio :-) [snip] Fuses won t protect
        Message 3 of 20 , Nov 11, 2006
          Ahh ,,but the built in safety fuse will trip during a lighnting or
          severe static event .

          Unfortunately that fuse is the radio :-) [snip]

          Fuses won't protect you if you are in contact with the lead in wire ! I
          grabbed a lead in wire once and got a nasty shock ! It was a very cold
          windy day, and after it happened I went outside to make sure the power
          line hadn't fallen on the antenna. All it was, was a static charge on
          the antenna wire. But it hurt as bad as a shock from the 117 volt AC
          power would or maybe even worse ! I later switched to insulated antenna
          wire to help keep the static off the antenna. I'm a ham now for the last
          11 years, and I still use insulated wire for my antennas !

          Rick McKee - KC8AON - Southern Ohio
          http://www.angelfire.com/electronic2/qrp
          http://www.angelfire.com/electronic2/qrp/forsale.html
          Monthly QRP Field Day Group: http://groups.yahoo.com/group/mqfd
          With God all things are possible <><
        • Laurence Taylor
          ... If you do exactly that, you ll short your signals to earth! I take it you meant the Ae and E terminals. I should think you d get excellent reception - and
          Message 4 of 20 , Nov 15, 2006
            In message <ej2ung+qc2v@...> "Danny" writes:

            > What do you think about the following. I know a place where I can go
            > anytime. This place is a mile away from any power line. If I put a 10
            > feet pipe in the ground and a 250 feet of vertical wire attached to a
            > helium balloon and I connect both wires to the antenna input of a
            > receiver, what could be the predicted result of a such arrangment?

            If you do exactly that, you'll short your signals to earth!
            I take it you meant the Ae and E terminals.

            I should think you'd get excellent reception - and
            transmission, if you ue it for that. Better still with an
            ATU.

            The problem, of course, is that baloons tend to blow about
            in the wind, so you'd have to anchor it, but it's certainly
            a good way of getting a decent aerial out!

            It's not an original idea, though; Radio Marti in Florida
            and Radio Laser in Europe both experimented with baloon-
            mounted aerials.

            rgds
            LAurence

            ... >°<<<=< (Thread Herring)
            ~~~ Tag-O-Matic V.13F
          • Greg W:-)
            ... SNIP ... And marconi did it 3 thousand years ago too ,,well , maybe not exactly 3 thousand years ,,but a long time ago anyway. :-P gregW:-)
            Message 5 of 20 , Nov 15, 2006
              --- In loopantennas@yahoogroups.com, Laurence Taylor <lozt@...> wrote:
              >
              SNIP
              > It's not an original idea, though; Radio Marti in Florida
              > and Radio Laser in Europe both experimented with baloon-
              > mounted aerials.
              >
              > rgds
              > LAurence


              And marconi did it 3 thousand years ago too ,,well , maybe not exactly
              3 thousand years ,,but a long time ago anyway. :-P

              gregW:-)

              http://www.swdxer.co.nr/

              =======================================================================
            • dariusfranke
              I think also some of the winners of the crystal set DX contests do much the same technique, so it must be pretty effective - more wire up higher , as they
              Message 6 of 20 , Nov 15, 2006
                I think also some of the winners of the crystal set DX contests do
                much the same technique, so it must be pretty effective - 'more wire
                up higher' , as they say...

                Dave



                --- In loopantennas@yahoogroups.com, "Greg W:-)" <onegammyleg@...> wrote:
                >
                > --- In loopantennas@yahoogroups.com, Laurence Taylor <lozt@> wrote:
                > >
                > SNIP
                > > It's not an original idea, though; Radio Marti in Florida
                > > and Radio Laser in Europe both experimented with baloon-
                > > mounted aerials.
                > >
                > > rgds
                > > LAurence
                >
                >
                > And marconi did it 3 thousand years ago too ,,well , maybe not exactly
                > 3 thousand years ,,but a long time ago anyway. :-P
                >
                > gregW:-)
                >
                > http://www.swdxer.co.nr/
                >
                > =======================================================================
                >
              • Danny
                ... would do ... into the ... but not an ... vertical ... but ... But given a ... has a ... match to 50 ... definitely ... you could ... the ... is for the ...
                Message 7 of 20 , Nov 18, 2006
                  --- In loopantennas@yahoogroups.com, Ken Javor <ken.javor@...> wrote:
                  >
                  > It certainly sounds impractical, but here is what that antenna
                  would do
                  > theoretically. First, I would not rely on a ten foot pipe driven
                  into the
                  > ground for a ground plane connection. That is a lightning ground,
                  but not an
                  > rf ground. You want 250' radials emanating from the point where the
                  vertical
                  > comes to ground. And I think you want a radial every 22.5 degrees,
                  but
                  > there are probably others here who have a better feel for that.
                  But given a
                  > decent ground plane, at 1 MHz you have a quarter-wave monopole. It
                  has a
                  > source impedance of about 36 Ohms, so it is a reasonably close
                  match to 50
                  > Ohms. If you had to pick between 50 and 75 Ohm coax, you would
                  definitely
                  > use 50 Ohm. However if you had a 2:1 unun or step-up transformer,
                  you could
                  > use 75 Ohm coax.
                  >
                  > The effective height of a half-wave dipole into a matched load is
                  the
                  > wavelength divided by 6.28 (2*pi). I think it is the same for a
                  > quarter-wave monopole, but the matching impedance is half what it
                  is for the
                  > dipole. The effective height is the transfer function between the
                  rf field
                  > intensity impinging on the antenna and the rf potential the antenna
                  delivers
                  > into a matched load. Thus:
                  >
                  > Vrcvr = E * he
                  >
                  > where
                  >
                  > Vrcvr = is rf potential delivered into matched load, Volts or
                  microvolts
                  > E = rf field intensity, Volts per meter or microvolts per meter, and
                  > he = lambda/(2*pi) = effective height, meters
                  >
                  > In this case, he = 48 meters. If your receiver has a sensitivity
                  of one
                  > microvolt, that means you can receive a signal strength of 1/48
                  > microvolt/meter, which is very good indeed.
                  >
                  > However, in order to do this your receiver would have to have very
                  good
                  > front end filtering to eliminate responses to stronger signals at
                  nearby
                  > frequencies, and of course you would have to be somewhere where no
                  other
                  > signal at the same frequency will overpower the signal of
                  interest. There
                  > is some lower level of "galactic" noise below which there is no
                  point in
                  > trying to improve sensitivity, because the background noise will
                  swamp
                  > everything out. I think that is where we are at with this design.
                  This is
                  > why a tuned loop would be ever so much more practical.
                  >
                  > In contrast to that, I have a very sensitive VLF (14 - 30 kHz)
                  receiver used
                  > on a Polaris class submarine dating from the 1960s. It has a
                  sensitivity of
                  > -153 dBm or 46 dB below one microvolt (1/200 microvolt). That
                  sensitivity
                  > is unusable on land - it was designed for an underwater antenna.
                  Because
                  > sea water is conductive and attenuates rf, the antenna operates in
                  an rf
                  > pristine environment where you can use all the sensitivity you can
                  get.


                  Thanks to everyone for your reply. Greatly appreciated.
                  Danny
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