[Antennas] Take off angles for short vertical

Fri Sep 8 11:02:07 EDT 2006

At 04:29 PM 9/7/2006, you wrote:
>I just installed DXLOG and among all it's many features is one called 
>PropView.
>It's requesting I enter take off angles for the various bands from 160m to 
>10m.
>>I need help on this please, as I have no clue what they are.
>>My antenna is a 12 foot tall center loaded vertical (tuned for 40m) 
>located at a height of 20 feet, on a flat gravel and tar roof. (*not metal 
>roof*)
>>For a ground it has sixteen, 13 foot long radials at the base, where it is 
>matched for 40m. All other bands are tuned with a tuner in the shack. 
>There is a coaxial balun (8 turns of coax) at the base of the antenna and 
>about 60 feet of coax to the shack from there.
>>What take off angles would the group suggest I use for:
>160m
>80m
>60m
>40m
>30m
>20m
>17m
>15m
>12m
>10m
>>TIA for the help.

Doing a quick and dirty model in NEC gives the following:
160m - 25º
80m - 25º
60m - 24º
40m - 21º
30m - 19º
20m - 16º
17m* - 14º & 52º
15m* - 47º & 13º
12m* - 41º & 12º
10m * - 36º & 12º
* - Two lobes with strongest listed first.
BTW: That's a pretty small antenna for multi-band operation. Efficiency is 
quite poor on the lower frequencies and nothing to brag about on the higher 
ones.
Hope this helps.
73,
Danny , K6MHE
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