[Moon-net] minimuml dish size

[Edward Cole]

At 11:10 AM 4/25/2008, on4iq at telenet.be wrote:
>Hi all
>would like to know if a 3m dish is more suited for 13cm than 23cm
>
>tnx
>
>Johan

Actually, they are equal.  Pathloss increases with the square of 
frequency; dish gain increases with the square of frequency.  So if 
everything else is the same they would work equally well.  Since 
above 1000 MHz sky temperature is fairly minimal up to 12-GHz, a 
ten-foot (3-meter) dish will work equally well over this frequency span.

This is an artifact of aperture which is collecting an equal amount 
of energy.  Antenna gain is too often regarded as the determinate 
factor, whereas collecting area is really what matters in 
reception.  Below 1-GHz the dish becomes too small in wavelength to 
perform well.  Above 12-GHz Gallactic and Atmospheric noise becomes a 
bigger factor in the overall performance.

73 Ed - KL7UW