[Moon-Net] 2.4M PRIME FOCUS / 2.4M OFFSET/ ALSO SEPTUM FOR 1296

Edward R Cole kl7uw at acsalaska.net
Tue Nov 22 00:54:38 CET 2016


Serge,

Just my opinion but if you can acquire an offset feed dish I suggest 
its slightly better:
1.  Feed does not block part of the dish surface (no apparent shadow)
2.  It requires a narrower beamwidth feed that may improve rejection 
of ground noise pickup (lower sidelobes; better G/T)
3.  You can mount all the electronics at the feed eliminating 
feedline losses (max bang for the buck)
4.  Often these dish surface are rated to 10-12 GHz so multi-band use 
is greater.

The feed support would need to be robust to handle the higher weight 
at the feed.
Dish may be fiberglass vs mesh so heavier weight.
Cost may be higher

Az-El requirements are the same.

Offset dish needs a feed designed for a F/d of 0.6-0.7 (W2IMU would 
work).  Ordinary septum would not be good.
I believe VE4MA is using one on 24/47 GHz so ask him about feedhorns.

I have a idle 1.8m offset feed dish I am considering for 10-GHz 
use.  It used to be our satellite-TV dish until recently switching to 
Direct-TV (which included free dish and HD receiver).  Recently 
occurred to me that 6-foot (1.8m) makes it a candidate for portable 
use with our RV trailer.
http://www.kl7uw.com/1.8m_dish.jpg

73, Ed - KL7UW

At 12:00 PM 11/21/2016, serge wrote:
>Which is best a 2.4M prime focus dish or a 2.4M offset dish? & WHY? 
>What kind of septum would you use on both dishes for 1296???
>Thank you
>Serge, VE1KG
>_______________________________________________
>Moon-Net posting and subscription instructions are at 
>http://www.nlsa.com/nets/moon-net-help.html

73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag Business e-mail:
     dubususa at gmail.com 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.pe1itr.com/pipermail/moon-net/attachments/20161121/22463f92/attachment.html 


More information about the Moon-net mailing list