Re: Directive Systems 3/6cm dual feed


John Lemay
 

Bernie

 

Disclaimer – I’m still learning about microwave dishes and feeds, so I’m prepared to be corrected ……..

 

Directive Systems say that their dual band feed is designed for dishes with an F/D of 0.39 to 0.45. That’s a pretty common  installation in a PF dish.

 

Commercial offset dishes generally require a feed designed for around 0.7 to 0.75 F/D. So it may well be that the lack of performance in your combination is due to non-optimum illumination of the offset dish. It is either over-illuminated (with lots of wasted energy outside the dish rim) or under-illuminated (which only uses a fraction of the dish surface).

 

There’s lots of info in the on-line W1GHZ antenna book. You just need to get your head around the geometry !

 

Regards

 

John G4ZTR

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Bernieg4hwa
Sent: 28 May 2022 11:27
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] Directive Systems 3/6cm dual feed

 

Hi Guys 

 

Wonder if anyone out there has had problems trying to get a directive systems dual feed for 3 and 6 cms working properly .I emailed directive systems some time back but received the "we have only used it on prime focus dishes" !!

 

I've tried it with my 65cm o/s dish and it doesn't seem as good as my original horn feed with flexi waveguide .On 6cms I couldn't hear the beacons I can on my grid pack parabolic dish for 6cms.

 

I also tried it with a 97cm o/s dish with very poor results on 3cms (didn't test 6cms at that time )

 

Any help would be appreciated .

 

73

 

Bernie

G4HWA

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