[TowerTalk] 15 meter yagi height for 6000 miles

[Jim Lux]

On 3/1/12 5:54 PM, Jim Lux wrote:
> On 3/1/12 4:45 PM, Bob K6UJ wrote:
>>
>> Has anyone used the HFTA program and can tell me the best height for a 15 meter yagi for 6000 miles.
>> Assuming there aren't any hills obscuring the take off angle.
>>
>> The carribean is about 6000 miles from my qth and from experimenting I have noticed that lowering the beam
>> down from 90 feet down to 50 feet it is markedly better for 15 meters.
>>
>> I just bought the new antenna handbook and plan to dive in and learn how to do the HFTA myself but was
>> hoping someone else had an idea of the best take off angle angle for 6000 miles on 15.
>> I believe 50 feet is about 3/4 wavelength high and gives me a 20 degree takeoff angle on 15.
>> Hope this all makes sense, hihi.
>>
>
> There's some example charts in the Antenna Book that might work for you.
>    Pick another path that's of comparable length and see what it says.
> Europe is about 6000 miles from 6-land, isn't it?
>



Here's the antenna book data for LosAngeles to EU  (LA to Paris is about 
6000 mi).  It looks like you want an angle around 3-5 degrees, and maybe 
a bump around 8-10 degrees.  These numbers come from VOACAP, I believe, 
so you could get a copy of that load it up, and run it for your link.

HFTA would then tell you how high to make the antenna to make that first 
big lobe at 3 degrees.

Los Angeles, Ca to Europe
Elev      80m    40m    30m    20m    17m    15m    12m    10m
  1        2.5    6.6    4.1    6.8    4.8    1.8    0.0    0.0
  2        4.1    9.1   10.8    6.7    9.6    4.9    4.6    5.6
  3        4.2    7.0   15.3   13.7   17.5   20.2    6.2    0.0
  4       10.2   11.2   10.8    7.8   13.6   13.5    9.2    0.0
  5        6.2   10.2   14.2    5.1    5.6   12.3   15.4   22.2
  6        1.7    6.6   12.0    8.3    7.1    6.7    9.2   16.7
  7        3.5    3.3    8.1    8.6    6.8    7.4    9.2   16.7
  8        3.5    4.6    5.3   11.4    9.3    9.8   13.8   11.1
  9        9.3    5.6    2.7   10.0    7.6    9.2   13.8   22.2
10        5.4   11.2    1.6    5.0    6.5    4.9    9.2    0.0
11        5.2    6.5    4.4    5.0    3.4    3.7    3.1    5.6
12        3.5    2.5    4.1    5.0    1.7    1.8    1.5    0.0
13        7.5    1.0    2.8    2.1    2.8    1.2    0.0    0.0
14        6.0    1.6    0.7    2.3    1.4    0.0    0.0    0.0
15        4.6    4.5    0.4    0.6    1.4    1.8    3.1    0.0
16        2.9    3.3    0.1    0.4    0.6    0.0    1.5    0.0
17        4.3    2.4    1.2    0.5    0.3    0.6    0.0    0.0
18        4.6    0.2    0.4    0.5    0.0    0.0    0.0    0.0
19        3.4    0.7    1.1    0.4    0.0    0.0    0.0    0.0
20        1.6    0.6    0.0    0.0    0.0    0.0    0.0    0.0