Re: Dish Mesh information


John Lemay
 

Mike

 

If you download EME Planner by VK3UM, you will be able to experiment endlessly with the effect of different mesh sizes (along with different f/d, different dish sizes, different feeds etc.). A good starting point is to keep the gap in the mesh smaller than one tenth of a wavelength.

 

I made a 2m dish using aluminium mesh and it worked well, but I eventually concluded that the wires needed to be thicker than steel to get the same strength, and consequently the wind load went up. My current dish uses galvanised steel mesh – my mesh came from F H Brundle.

 

Your biggest challenge will be to make the ribs to an accurate profile. Mine were bent by hand in a heavy vice, bit by bit, with frequent checks against a drawn profile. The first one took hours, the last one just a few minutes. It might seem obvious to bend the material against a pre-formed rigid profile, but that requires you to understand and compensate for the inevitable springback.

 

Regarding aluminium sheet, remember that it has to be formed in three dimensions to obtain a parabola – in other words it is not a straight line between each rib. That’s not easy to explain !

 

John G4ZTR

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Mike GD6ICR
Sent: 18 May 2021 10:44
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] Dish Mesh information

 

I am considering building a dish from scratch. What is there a relationship between dish mesh size and frequency and aluminium or stainless (i know its heavier but more durable) or foil covered fibreglass or even lightweight aluminium sheet. I realize also that the solid type dishes have a much higher wind loading. But the aluminium sheet is free and I can form it into 6 or more sections. I have had a look at the W1GHZ microwave pages but would like to see how UK based amateurs have constructed them as we dont have the kind of suppliers US has. Any help would be appreciated.

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Mike GD6ICR IO74PF73TW

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