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Re: Q. for antenna experts!



A patch antenna is also a good choice, suggest a sprical package ( basket 
ball shaped) so that the wind has less effect on the package. QHA does have 
circular polorized side lobes, but the patch antenna is only 1/4 inch thick, 
has better axial ratio, better gain and the reflector can be part of the 
package.

Art,
KC6UQH
----- Original Message ----- 
From: "i8cvs" <domenico.i8cvs@tin.it>
To: "Jeff Kelly" <jkelly@bellatlantic.net>; "AMSAT-BB" <amsat-bb@amsat.org>
Sent: Saturday, May 05, 2007 8:22 AM
Subject: [amsat-bb] Re: Q. for antenna experts!


> ----- Original Message -----
> From: "Jeff Kelly" <jkelly@bellatlantic.net>
> To: <amsat-bb@amsat.org>
> Sent: Saturday, May 05, 2007 1:14 PM
> Subject: [amsat-bb] Q. for antenna experts!
>
>> On another list for High Altitude Balloons a question came up
>> on installing an 802.11 system on board and what antenna would
>> be best on the balloon.
>
> Hi Jeff, KT2K
>
> On board of the High Altitude Balloon the best circularly polarized
> antenna for 2.4 GHz is the Quadrifilar Helix Antenna or QHA
> Look please at the AMSAT Journal May/June 2004 page 6 to 10 for
> details to build it.
>
>> Circular polarization came up.
>
> RHCP on board of Balloon is convenient because the most part of ground
> stations are already equipped to receive RHCP on 2.4 GHz as they did with
> AO40
>
>> Of course
>> low cost - commercially available was key also.
>
> If you look at the above article you will realize that a Quadrifilar Helix
> Antenna for 2.4 GHz can be homebrewed at low cost in a few hours of job.
>
>>  Any suggestions
>> on the balloon side for 2.4?
>
> The Quadrifilar Helix Antenna is very light weight because do not
> requires a reflector but it radiates a circularly polarized wave all the
> way towards the earth.
>
>> I have seen low cost circular patch antennas
>> for 2.4.  Is that a good pattern for up to a 100,000 ft source?
>
> The Quadrifilar Helix Antenna was used on board of  OSCAR-7 for the
> 2304 MHz  telemetry Beacon as described in
>
> http://www.w2du.com/r2ch22.pdf
>
> and it's lobe as shown in Fig 22-5 is circularly polarized all the way
> around the pattern
>
>> Guess the balloon side should be LHCP?
>
> The ballon side can be RHCP or LHCP but considering that most
> radio hams are already using RHCP on the ground then RHCP on
> the ballon side is preferred.
>>
>> The balloon payload would be thrown around and spinning in flight.
>
> No problems using a QHA on board of a balloon as depicted in Fig 22-6
> and discussed by Walter Maxwell, W2DU in the above article.
>
>> Thanks for any ideas.
>>
>> Jeff
>> KT2K
>
> I hope this helps
>
> 73" de
>
> i8CVS Domenico
>
>
>
>
>
>
> _______________________________________________
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