[amsat-bb] Re: Mode S Antenna question

[Ronald Nutter]

What got me thinking about the circular polarized type of antenna is to 
minimize the signal dropouts from the satellite as it spins.  My other 
thought was to put a second antenna up, orient it horizontally and put a 
remote antenna switch in place so that I can flip between vertical and 
horizontal.  Is my idea sound or am I barking up the wrong tree ?

Ron
KA4KYI

Edward Cole wrote:
> At 05:26 AM 5/10/2008, Ronald Nutter wrote:
>> I have been using a 2.4 ghz Vagi antenna for my Mode S antenna the past
>> few days.  I am seeing quite a bit of signal droppout as AO-51 does a
>> little rotating.  With a circular polarized antenna do any better ?  I
>> have found a source for a 2.4ghz 10 db RHCP antenna and thought about
>> trying that.  I know I cant get it before AO-51 goes back to V/U mode
>> but thought I could try that next time.  The antenna I found has about a
>> 50 degree pattern so I should get decent coverage since I have it
>> pointed at a fixed elevation because I dont have an az/el rotor.
>>
>> Ron
>> KA4KYI
> 
> Ron,
> 
>  From what I have read on what others are using for 2.4 GHz (mode-S) on 
> AO-51 (or other Leo sats) a 10-dB circular pol. antenna should work 
> fine.  As far as using it without elevation control I cannot tell you 
> how that will work.  Ten dB may be a bit too narrow for best operation 
> at all elevations.  But the gain would be good to have for  the period 
> of time the satellite is within your beam.  I believe Bob Bruninga has 
> found that a fixed elevation of 20-degrees makes a good solution when 
> not moving elevation.
> 
> If the antenna is accessible you can experiment on what angle works best 
> by trying it at several angles.
> 
> I plan to build my self a simple corner reflector fed with a dipole 
> which should result in about 10-dB gain.  I also have an 85cm dish with 
> helix feed that was used for AO-40.  I have two 2.4 -GHz LNA's and two 
> Drake converters (123-MHz; 435-MHz output) so that any combination will 
> be possible when all is re-installed.  I have full az-el tracking.
> 
> 
> 
> 
> *****************************************************
> 73, Ed - KL7UW              BP40iq, 6m - 3cm
> 144-EME: FT-847, mgf-1801, 4x-xp20, 185w
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