[amsat-bb] Re: Antenna project with 2 ELK antennas

[Jean-François Ménard]

Le 8 août 2009 11:54, i8cvs<domenico.i8cvs at tin.it> a écrit :
> Hi Jean, VA2SS
>
> Since the ELK antenna is a log-periodic antenna covering a wide
> band from 2 meters and 70 cm it is difficult to connect 2 ELK in
> phase and gain 3 dB in 2 meters and 70 cm as well.
>
> Also it is difficult to connect 2 ELK with a phase offset of 90°
> to get circular polarization in 2 meters and 70 cm
>
> I would prefere to put one ELK horizontal and the other one
> vertical feeding each antenna with an individual coax line.
>
> Using a coax relay in the shack you can immediately switch
> from the Horizontal to the Vertical polarization.
>
> About the distance between the antennas over the plastic boom
> the distance is a function of the antenna gain and higher is the gain
> (in order do not overlap the aperture area of each antenna) larger
> must be the distance between booms
>
> Since the gain of the ELK in the lover 2 meters band is 6.6 dBd
> over the dipole or 6.6 +2.14 = 8.7 dBi over the isotropic then the
> aperture area wich is a circle perpendicular to the antenna boom
> can be computed using the following formula:
>
>                                   /  2
>                           G x /\
> Aperture area= ----------
>                           4 x Pi
>
> Since G= 8.7 dBi = 7.41 in power ratio
>
>                                            2
>                             7.41 x 2
> Aperture area= -------------- = 2.36 square meters
>                             4 x 3.14
>
> A circle with a geometrical area of 2.36 square meters
> has a radius of
>
>             \       /--------------------
> radius = \   /       2.36 / 3.14        = 0.86  meters
>                \/
>
> Hence the distance between the booms is 0.86 x2 = 1.72 meters
>
> In this condition both aperture areas are tangents but it is better
> to overlap the areas a 10 % to prevent the generation of side lobes
> so  that a distance of 1.55 meters between the antenna booms
> is recommended.
>
> I hope this helps
>
> 73" de
>
> i8CVS Domenico
>
> ----- Original Message -----
> From: "Jean-François Ménard" <jf.va2ss at gmail.com>
> To: "i8cvs" <domenico.i8cvs at tin.it>
> Sent: Saturday, August 08, 2009 4:00 PM
> Subject: Re: [amsat-bb] Antenna project with 2 ELK antennas
>
>
> Hi,
>
> I do not know much about antenna... But I tought that could be better
> for satellite this way... I did not do any search at this time about
> this project... it is only an idea that I had.
>
> If you have any suggestion for such project using 2 Elk antenna....
> please let me know.
>
> I don't want to spend much money at this moment... and I have only
> these 2 antenna.
>
Wow !!

Thanks !! This is the kind of answer that I really like.
I will try this with the recommendation you gave me. I'm not familiar
with all those formulas regarding antenna, so a little help time to
time is really helpful.... I like to learn, so you won't repeat the
same thing twice.

Thank again.

Best 73

J-F VA2SS

> 73
>
>
> 2009/8/8 i8cvs <domenico.i8cvs at tin.it>:
>> ----- Original Message -----
>> From: "Jean-François Ménard" <jf.va2ss at gmail.com>
>> To: "AMSAT Mailing list" <amsat-bb at amsat.org>
>> Sent: Thursday, August 06, 2009 10:44 PM
>> Subject: [amsat-bb] Antenna project with 2 ELK antennas
>>
>> Hi,
>>
>> I have 2 ELK antennas here, and I would like to do an experiment with
>> these two antennas. I would like to stack side by side, one vertical,
>> and one horizontal.
>>
>> 73
>>
>> Jean-François Ménard
>> VA2SS
>>
>> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>> AMSAT www.amsat.org / Member #37102
>> ARRL www.arrl.org
>> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>>
>> Hi Jean, VA2SS
>>
>> Staking 2 ELK antennas side by side,one vertical,and one horizontal
>> what type of polarization you plan to get ?
>>
>> 73" de
>>
>> i8CVS Domenico
>>
>>
>>
>>
>
>
>
> --
> Jean-François Ménard
> VA2SS
>
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> AMSAT www.amsat.org / Member #37102
> ARRL  www.arrl.org
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>
>
>
>
>
>
>
>
>



-- 
Jean-François Ménard
VA2SS

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
AMSAT www.amsat.org / Member #37102
ARRL  www.arrl.org
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=