[eagle] Re: Another idea on phased array configuration

John B. Stephensen kd6ozh at comcast.net
Sun Apr 29 00:18:40 PDT 2007


It seems to me that it would be advantageous to design for operation with 
less than the maximum number of elements. If only 25 of 36 elements need to 
be used, 11 can fail and be replaced before the link budget degrades 
significantly. If more than 25 elements are required to get 18 dBic, then it 
would be advantageous to fly 40-50% more elements than that number.

73,

John
KD6OZH

----- Original Message ----- 
From: "Matt Ettus" <matt at ettus.com>
To: "John B. Stephensen" <kd6ozh at comcast.net>
Cc: "Louis McFadin" <w5did at amsat.org>; "Robert McGwier" 
<rwmcgwier at gmail.com>; "AMSAT Eagle" <Eagle at amsat.org>; <K3IO at verizon.net>
Sent: Sunday, April 29, 2007 06:57 UTC
Subject: Re: [eagle] Re: Another idea on phased array configuration


>
> So what?  We can have, and were planning on having, an 18dB gain array. 
> That doesn't mean we need to turn any elements off.
>
> Matt
>
> John B. Stephensen wrote:
>> The spreadsheet distributed early last year shows a 9 degree squint angle 
>> at the leading and trailing horizons at apogee. An antenna with an 18 
>> degree half-power beamwidth has a gain of 41000/(HPBW^2) = 127 = 21 dBi. 
>> It would be best to illuminate the earth with a loss of only 1 dB at the 
>> edges and the -1 dB beamwidth is going to be 2/3 or less of the -3 dB 
>> beamwidth. The gain should then be adjusted by 4/9 or 3.5 dB less. This 
>> would be 17.5 dBi.
>>
>> 73,
>>
>> John
>> KD6OZH
>>
>> ----- Original Message ----- From: "Matt Ettus" <matt at ettus.com>
>> To: "John B. Stephensen" <kd6ozh at comcast.net>
>> Cc: "Louis McFadin" <w5did at amsat.org>; "Robert McGwier"
>> <rwmcgwier at gmail.com>; "AMSAT Eagle" <Eagle at amsat.org>; 
>> <K3IO at verizon.net>
>> Sent: Saturday, April 28, 2007 19:57 UTC
>> Subject: Re: [eagle] Re: Another idea on phased array configuration
>>
>>
>>>
>>> John B. Stephensen wrote:
>>>> Since the generated beam needs to cover the entire earth from a maxmum 
>>>> of
>>>> 35,000 km in alttude, the beam can't be made very narrow. I don't think
>>>> that all 36 or 43 elements ever need to be on at one time. Many could 
>>>> be
>>>> held in reserve.
>>>
>>>
>>> Where do you come up with this?  What sort of analysis?
>>>
>>> Matt
>>>
>>>
>>
> 



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