Modifying Prodelin Series 1250 from C to Ku band

Put here by forum admin from email..

>>>Modding an old Prodelin Series 1250 from C to Ku, on a remote island...

Have Ku feed assembly but need to position it on the C "platform"...
Question about the focal length: compared to the position of the
existing C horn mouth, where should the Ku window be located? Same? A
bit closer to reflector? Or someone has the "ABCD" dimensions for Ku?
Any estimate highly appreciated!

Thank you

Cheers

Christian

Owner, ICTL
Main Camp, Kiritimati Is.
EASTERN Kiribati
ictl@linnixislands.com
+1 808 441 1939   -voicemail n fax to/from email
Time Zone: GMT-10 (Hawaii)

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Reply:

I think this is the key document that you need to download and print:

http://www.gdsatcom.com/vsat/Technical_Docs/feed_location_drawings/TD0641.pdf

It has ALL the ABCD measurements.

The document shows ABCD dimensions for various feed window diameters; so good for C or Ku band.

The phase centre of the feed should match focal point of the dish.

The phase centre of a feed is known only to the manufacturer. For a conical horn the phase centre may be at the aperture or further down inside.

If you examine the ABCD lengths, it is to be observed that as you reduce the feed diameter the distance the feed window needs to be from the dish increases. This indicates that for the Prodelin feeds the phase centre is deep down inside the conical horn.


Best regards, Eric.