Hi All,
I received many comments about this. Thanks for your inputs.
First I need to say that, in first place, if I shared my results here, that was
because I found them interesting if not disturbing.
Both antennas were modeled horizontal.
In both cases MMana was set to run simulation on the model at 3m height over «
real ground ».
The Moxon model was created yesterday.
The Jungle-Job however I had it from a former simulation for a multi-band
jungle-job using coupled resonator.
The problem was the Jungle-Job model has a design that included an offset of
10m! (All wires were with Z=10m)
That explains the numbers.
The Jungl-job is still better than the Moxon, but only by 1dB.
Not worth the increase in size. It might still be easier to
assemble/disassemble for portable, though.
I apologize for the « noise »…
To Rick N6RK, sourcing lightweight 3,2m and 4,7m fishing pole is easy and
cheap. Anything longer is difficult to find and very expensive (for my
budget)...
To Pres N6SS, yes I hope to be participating in the AA DX SSB next september.
73,
Yan.
---
Yannick DEVOS - XV4Y
http://www.qscope.org/
http://xv4y.radioclub.asia/
Le 9 août 2014 à 05:02, Richard (Rick) Karlquist <richard@karlquist.com> a
écrit :
>
>
>
> On 8/7/2014 8:48 PM, Yan (XV4Y) wrote:
>
>> At 10°, the Jungle Job still has 7,4dBi gain, while the Moxon shows a
>> -2,3dBi loss…
>
> This is just a modified 2 element Yagi. Nothing that will
> magically give it good low angle radiation. I modeled
> a dipole, ZL special, and 8JK at 10 feet high, 10 degrees
> elevation vs the same antennas in free space. All three
> were down about 9 dB 10 feet over ground vs free space.
> The relative gains of the three antennas over ground were
> within a few tenths of a dB compared to their free space
> rankings. For the Jungle Job to have 7.4 dBi at 10 feet,
> it would need to have 16 dBi in free space. No way.
> In fact, it would be a stretch for it to have 7.4 dBi
> even in free space.
>
> What we can conclude is that ground gain is a function
> of height, not antenna type. If someone has a counter
> example, I would love to hear about it.
>
> In any event, a half wave vertical (IE Parz end fed)
> will probably beat anything horizontally polarized
> at 10 feet high on 20 meters, and the vertical virtually
> fits in your pocket. Add a 33 foot telescoping fishing
> pole if necessary for support. Very portable.
>
> Rick N6RK
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|