Ground losses for both antennas were included to the extent that EZNEC
Sommerfield-Norton ground is accurate. At the heights used in these
examples, that should be a good estimate.
What is "real world" height varies a lot depending on whose station it is.
Jerry, K4SAV
Joe Subich, W4TV wrote:
>W4SAV wrote:
>
>
>
>>Well, my original statement is not 100% true for all heights, and
>>neither is yours. Here are some EZNEC numbers for a three
>>element Yagi turned either vertically of horizontally.
>>
>>
>
>Even at 20 meters, 150 feet or more is a bit out of reach for most
>people. However, your statement is correct at heights that begin
>to approach free space conditions (5 to 10 wavelength). With those
>heights horizontal antennas loose their "ground reflection gain"
>and the vertical antennas lose the ground losses (which are not
>reflected in your models).
>
>When one reaches true free space conditions, the antennas will
>have identical gain but amateur HF antennas are located in the
>real world (above ground) unless your station is located on ISS.
>
>73,
>
> ... Joe, W4TV
>
>
>
>
>>-----Original Message-----
>>From: towertalk-bounces@contesting.com
>>[mailto:towertalk-bounces@contesting.com] On Behalf Of K4SAV
>>Sent: Wednesday, June 20, 2007 11:01 AM
>>To: towertalk@contesting.com
>>Subject: Re: [TowerTalk] Trapped Tribanders Turned Vertical
>>
>>
>>K4SAV wrote:
>>The higher the antennas are, the less difference in gain
>>there will be between mounting vertically and horizontally.
>>
>>W4TV wrote:
>>Not true ... the vertical beam will always miss the "ground
>>gain" and will lag the horizontal antenna by three to six dB.
>>
>>------------------------
>>Well, my original statement is not 100% true for all heights, and
>>neither is yours. Here are some EZNEC numbers for a three
>>element Yagi turned either vertically of horizontally.
>>
>>Height ___ Horz Antenna ______ Vert Antenna ____ Gain Difference
>>20 ______ 9.6 dBi at 36 deg ___ 4.8 at 17 deg ______ 4.8 dB
>>30_______11 dBi at 28 deg _____ 5.7 dBi at 15 deg __ 5.3 dB
>>35 _____ 11.6 dBi at 25 deg ____5.9 dBi at 13 deg __ 5.7 dB
>>40 _____ 11.9 dBi at 23 deg ___ 6 dBi at 12 deg ____ 5.9 dB
>>80 _____ 12.7 dBi at 12 deg ___ 8 dBi at 9 deg _____ 4.7 dB
>>100 ____ 12.9 dBi at 10 deg ___ 8.8 dBi at 8 deg ___ 4.1 dB
>>120 ____ 12.9 dBi at 8 deg ____ 9.4 at 7 deg _______ 3.5 dB
>>150 ____ 13 dBi at 7 deg ______ 10.1 dBi at 6 deg __ 2.9 dB
>>200 ____ 13.2 dBi at 5 deg ____ 10.8 dBi at 5 deg __ 2.4 dB
>>300 ____ 13.1 dBi at 3 deg ____ 11.6 dBi at 3 deg __ 1.5 dB
>>
>>When a horizontal antenna is placed very close to the ground, like 35
>>feet or less for a 20 meter antenna, the ground loss for the
>>horizontal
>>antenna increases dramatically making my original statement
>>not exactly
>>accurate. However, above about 40 feet, the gain difference
>>between a
>>horizontal and vertically mounted antenna steadily decreases.
>>
>>Jerry, K4SAV
>>
>>Joe Subich, W4TV wrote:
>>
>>
>>
>>>>The higher the antennas are, the less difference in gain
>>>>there will be between mounting vertically and horizontally.
>>>>
>>>>
>>>>
>>>>
>>>Not true ... the vertical beam will always miss the "ground
>>>gain" and will lag the horizontal antenna by three to six dB.
>>>Over salt water the vertical beam will have more gain at
>>>lower take off angles but its maximum gain will never equal
>>>that of the same beam mounted horizontally.
>>>
>>>A good frequency for comparison is 10 meters as the height
>>>required for a horizontal antenna to have a take off angle
>>>similar to that of the vertical antenna becomes reasonable.
>>>A vertical dipole at 55' (center) over perfect ground (salt
>>>water) has a peak gain of 4.13 dB at 7 degrees. A horizontal
>>>dipole at 55' has a peak gain of 8.08 dBi at 9 degrees (7.63
>>>dBi at 7 degrees). Move the antennas to 70 feet and the
>>>gains are 4.71 dBi for the vertical dipole and 7.92 dBi for
>>>the horizontal dipole (at 7 degrees).
>>>
>>>73,
>>>
>>> ... Joe, W4TV
>>>
>>>
>>>
>>>
>
>
>
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