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Re: BBQ Dish Gain Data



Edward R. Cole wrote:
> Thanks, Gene:
> 
> Central States and other VHF/UHF groups do a good job of making the
> "reality" measurements to compare with our theoretical assumptions.  To
> summarize, it looks like the larger BBQ dish (labeled 38x26-inch and
> submitted by K5GNA) measured at 20.8 dBi, while the smaller BBQ 17x22-inch
> dish came in at best gain of 18.3 dBi.
> 
> These two data points kind of establish the upper limit of performance that
> one should expect...I would use these gains in the AO40v2.0 spreadsheet for
> estimating purposes.
> 
> Interesting to note that a 0.9m dish submitted by K5VH measured at 22.2
> dBi...I am using an 85cm-offset feed dish which is approx the same size (he
> uses a loop feed vs my helix).  This is approx. -3dB of my est. gain.
> 
> Also interesting to see the effects that choice of feeds make. 
> 

Okay, so 38x26 = 988 sq inch.
.9m = 35.4 inches area = pi r^2 = 3.14 * (35.4/2) * (35.4/2) = 983 sq inch

Would that be about 22.2db versus 20.8db or about 1.4db difference for the
BBQ factor?   Is that the whole difference?  Or is there something else
going on here?

Has anyone ever tried to make a monster BBQ dish, like 10ft orsomething?
It'd seem to me, that'd be easier to rotate than a solid/mesh dish of the
same size.
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