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Re: [30MDG] Take-Off-Angle (TOA)

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  • John Mac
    Hi all... Yes take-off angle is important and I have seen a 3/8wl Vertical for 2m, but I have yet to see one for 30m or any other band....how do you go about
    Message 1 of 4 , Aug 2, 2013
      Hi all...

      Yes take-off angle is important and I have seen a 3/8wl Vertical for
      2m, but I have yet to see one for 30m or any other band....how do you
      go about feeding it, I have put some numbers into the software and
      using 17m as the test dummy( as I have ally for that size here now
      )...still not able to get 1:1 matching...not without a 2:1 Balun
      ...The 2m version I saw, was able to be matched to a 50 ohm coax..

      John

      On 8/1/13, Scott Currier <scott_currier@...> wrote:
      > I agree with the 1/2 wave rule of thumb.
      >
      > Fortunately 50 feet is quite doable in many locations.
      >
      > As for gain, gain and directivity start the minute you go longer than 1/2
      > wavelength.
      >
      > If you use a full wave dipole, you can expect about 1.8 db of gain over a
      > 1/2 wave with a similar pattern.
      >
      > Increase the length to .64 wavelength on each side and you're up to about
      > 3db of gain with a similar but sharper dipole type pattern.
      >
      > Go beyond that and the pattern get's more complex as the length of the
      > antenna is increased.
      >
      > I was comparing my 80 meter OCF on 10 meters with a 10 meter dipole. In some
      > cases the OCF was lOT stronger. Of course the OCF on 10 meters was 4
      > wavelengths long so the pattern will be quite complex with lots of peaks and
      > nulls.
      >
      > 73 and have a nice day.
      >
      > Scott KT1B Haverhill, MA
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      > To: 30mdg@yahoogroups.com
      > CC: ki5fj@...
      > From: jen1joeo@...
      > Date: Tue, 30 Jul 2013 07:04:51 -0700
      > Subject: [30MDG] Take-Off-Angle (TOA)
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      > Folks please remember the
      > half-wavelength rule
      > for horizontal antennas.
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      > A low TOA (DX antenna) from a horizontal
      > Yagi or a flat top dipole is only possible when
      > the antenna is a minimum of 49 Ft up in the air.
      > Half-Wavelength on 30-Meter Band is 49 Ft.
      >
      > There is no free lunch.
      > Low TOA with directivity gain
      > can be obtained by a horizontal antenna
      > when it is size is over 4 wavlengths.
      >
      > A 3/8 wavelength (37 ft) vertical with
      > 20 radials is a mechanically reasonable
      > antenna with a LOW TOA!
      >
      > 73
      > Joe O
      > NNNN
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    • John Mac
      Hi all.... Tried the design again....now get a 1.2:1 swr in the software....Flat pattern, as its on 17m it is up 3m, has a 17.5 deg take-off. So now some
      Message 2 of 4 , Aug 3, 2013
        Hi all....

        Tried the design again....now get a 1.2:1 swr in the software....Flat
        pattern, as its on 17m it is up 3m, has a 17.5 deg take-off. So now
        some testing and I just may try the bigger one for 30m..

        John..

        On 8/3/13, John Mac <vk2fak@...> wrote:
        > Hi all...
        >
        > Yes take-off angle is important and I have seen a 3/8wl Vertical for
        > 2m, but I have yet to see one for 30m or any other band....how do you
        > go about feeding it, I have put some numbers into the software and
        > using 17m as the test dummy( as I have ally for that size here now
        > )...still not able to get 1:1 matching...not without a 2:1 Balun
        > ...The 2m version I saw, was able to be matched to a 50 ohm coax..
        >
        > John
        >
        > On 8/1/13, Scott Currier <scott_currier@...> wrote:
        >> I agree with the 1/2 wave rule of thumb.
        >>
        >> Fortunately 50 feet is quite doable in many locations.
        >>
        >> As for gain, gain and directivity start the minute you go longer than 1/2
        >> wavelength.
        >>
        >> If you use a full wave dipole, you can expect about 1.8 db of gain over a
        >> 1/2 wave with a similar pattern.
        >>
        >> Increase the length to .64 wavelength on each side and you're up to about
        >> 3db of gain with a similar but sharper dipole type pattern.
        >>
        >> Go beyond that and the pattern get's more complex as the length of the
        >> antenna is increased.
        >>
        >> I was comparing my 80 meter OCF on 10 meters with a 10 meter dipole. In
        >> some
        >> cases the OCF was lOT stronger. Of course the OCF on 10 meters was 4
        >> wavelengths long so the pattern will be quite complex with lots of peaks
        >> and
        >> nulls.
        >>
        >> 73 and have a nice day.
        >>
        >> Scott KT1B Haverhill, MA
        >>
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        >> To: 30mdg@yahoogroups.com
        >> CC: ki5fj@...
        >> From: jen1joeo@...
        >> Date: Tue, 30 Jul 2013 07:04:51 -0700
        >> Subject: [30MDG] Take-Off-Angle (TOA)
        >>
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        >> Folks please remember the
        >> half-wavelength rule
        >> for horizontal antennas.
        >>
        >> A low TOA (DX antenna) from a horizontal
        >> Yagi or a flat top dipole is only possible when
        >> the antenna is a minimum of 49 Ft up in the air.
        >> Half-Wavelength on 30-Meter Band is 49 Ft.
        >>
        >> There is no free lunch.
        >> Low TOA with directivity gain
        >> can be obtained by a horizontal antenna
        >> when it is size is over 4 wavlengths.
        >>
        >> A 3/8 wavelength (37 ft) vertical with
        >> 20 radials is a mechanically reasonable
        >> antenna with a LOW TOA!
        >>
        >> 73
        >> Joe O
        >> NNNN
        >>
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        >
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