Topband: INV. L vs Vertical

[Roger D Johnson]

cris blak wrote:
> Hello all,
>
> I did some simulation on MMANA-GAL with INV. L and 1/4 WL vertical for 160m band.
>
> I want to share with you some findings and I'll be glad to debate your experience either "on-air" or in theory.
>
> We have 3 antenna to compare:
>
> 1. INV. L with the following design:
>
> vertical section = 11m
> horizontal section slopping down to 9m = 28m
> wire diameter = 2mm
>
> 2. INV. L with the following design:
>
> vertical section = 28m
> horizontal section slopping down to 9m = 11m
> wire diameter = 2mm
>
> 3. 1/4WL Vertical with the following design:
>
> vertical section = 39m
> wire diameter = 2mm
>
> * All antennas will use a 0.5mm thickness radials as enumerated below.
>
> Evaluation criterion:
>
> All of the following criterion vs number of radials
> 1. Vertical radiation angle
> 2. Gain
> 3. horizontal radiation pattern (F/B ratio)
>
>
> a. 5 radials
> 1.1 = 28 degree
> 1.2 = 2.77dBi
> 1.3 = 2dB
>
> 2.1 = 24 degree
> 2.2 = 1.76dBi
> 2.3 = 0.1dB
>
> 3.1 = 23 degree
> 3.2 = 1.62dBi
> 3.3 = 0dB
> =================
> b. 10 radials
> 1.1 = 27 degree
> 1.2 = 2.88dBi
> 1.3 = 1.7dB
>
> 2.1 = 24 degree
> 2.2 = 2.02dBi
> 2.3 = 0.1 dB
>
> 3.1 = 22.9 degree
> 3.2 = 1.84dBi
> 3.3 = 0dB
> ================
> c. 30 radials
> 1.1 = 20 degree
> 1.2 = 3.06dBi
> 1.3 = 1.2dB
>
> 2.1 = 23 degree
> 2.2 = 2.64dBi
> 2.3 = 0.1dB
>
> 3.1 = 22.3 degree
> 3.2 = 2.4dBi
> 3.3 = 0dB
> ================
> d. 50 radials
> 1.1 = 18 degree
> 1.2 = 3.16dBi
> 1.3 = 0.9dB
>
> 2.1 = 22 degree
> 2.2 = 2.98dBi
> 2.3 = 0.1dB
>
> 3.1 = 21.5 degree
> 3.2 = 2.75dBi
> 3.3 = 0dB
> ================
> e. 100 radials
> 1.1 = 15 degree
> 1.2 = 3.28dBi
> 1.3 = 0.5dB
>
> 2.1 = 19 degree
> 2.2 = 3.45dBi
> 2.3 = 0.1dB
>
> 3.1 = 19.9 degree
> 3.2 = 3.27dBi
> 3.3 = 0dB
> ================
> f. 360 radials
> 1.1 = 10 degree
> 1.2 = 3.42dBi
> 1.3 = 0.2dB
>
> 2.1 = 14 degree
> 2.2 = 4.14dBi
> 2.3 = 0dB
>
> 3.1 = 15.1 degee
> 3.2 = 4.12dBi
> 3.3 = 0dB
>
> Putting those values on a graph, one could observe easily the following treads:
>
> Vertical radiation angle:
>
> Increasing the number of radials, the lower the angle. The best is INV. L with 11m vertical section. I did simulate one with 1000 radials and I got 7 degree!
> The poor is the Vertical!
>
> Gain:
>
> The Vertical and INV. L with 28m vert. section has increasing the gain with radial numbers. The INV. L with 11m vert. section has an almost flat gain (not very much dependent of radial numbers);
>
> F/B ration:
>
> For the Vertical and INV. L with 28m vert. there is no difference of the F/B (zero dB).
> For INV. L with 11m vert. section there is about 2dB F/B ratio with poor radials.
>
> Overall conclusion:
>
> I don't know why people struggle to built big verticals for DX because a better elevation angle (vertical radiation angle) could be achieved with an INV. L (as were demonstrated above). Gain is not a problem because the difference is small.
>
> One plus for the Vertical is that it has a big null on the bigger elevation angle. That means, the local station (within 1000Km radius) will be highly attenuated. This is not the case with either 28m or 11m vert. secion of INV. L.
>
> Think about this and I'll look forward for your thoughts/experience.
>
> 73 de YO3FFF
> Cristi 
>
>  
>
>
>   

Cristi....

I think you have fallen into a trap! MMANA is based upon the MININEC 
program and
will NOT properly model horizontal wires close to ground. Radial systems 
will not affect
the angle of radiation unless they are extremely large (several 
wavelengths). See W4RNL's
site for more information.

73, Roger

-- 
Remember the USS Liberty (AGTR-5)
http://ussliberty.org/