Re: 3.4G feed horn dimensions ?


John Fell
 

Nick,
The standard tin length is good enough - the probe point to the end short of the waveguide ( Tin can) is more important .
No doubt Peter's data will be fine .
The Chaparral flange addition is to enforce a better distribution  illumination of the dish surface for higher F/d ratio .

The open ended can without any flange addition will work fine with a near prime (0.25 F/d ratio ) reflector , which requires near to 90 degree feed angle .

An alternative , easier to make , flange is a Super VE4MA .This works well with dishes in  the 0.55 to 0.8F/d range , such as the majority of domestic  Sat dishes .It is also possible to adjust the flange position although the data given on the W1GHZ website is close enough to fix the position .

73/Seasons Greetings 

John
G0API

On Sun, 6 Dec 2020 at 14:34, Nick Gregory G0HIK via groups.io <nickg0hik=googlemail.com@groups.io> wrote:
The 9cm's SG-Labs arrived yesterday and I'm cant wait to get going.

I've found on the G3PHO site a "Soup Tin" feed horn.

I've copied it and the SWR is in the green straight away :)

But what length should I make the waveguide section, it is not mentioned in the article ?

And what does a Chaparral horn actually do ?

Nick G0HIK
 






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