[time-nuts] GPS backup for the stationary time and frequencyuser

[Brian Kirby]

  20 log(base10) (diameter in meters) + 20log(frequency in ghz) +17.8 = dbi

On 10/8/2010 8:39 PM, jimlux wrote:
> Magnus Danielson wrote:
>> On 10/08/2010 08:22 PM, jimlux wrote:
>>> B
>
>>> You might do just as well with a flat cookie sheet.
>>
>> Well, a 1 m dish gives you 48 dB gain at L1 if I calculate correctly. 
>
> I don't think so..48dBi would be huge...A numerical gain of 48 I can 
> believe:
>
>  let's say we have an antenna that is 2x3 wavelengths (40x60cm, 1.5 
> GHz = 20 cm) or 6 square wavelengths. the gain is 4 pi * A, or about 
> 75. But in reality, the efficiency is typically no better than 50% 
> (because of sidelobes, illumination, etc.)... Call 66% to be sporty, 
> and you've got a numerical gain of 50, or 17dBi.
>
>
>
>
>> The normal antenna is at 6 db of antenna gain?
>>
>> Even if less than perfect, not too big size is needed to get 
>> meaningful antenna gain.
>>
>> Cheers,
>> M
>
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