[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
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
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.
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???
>Moon-Net posting and subscription instructions are at
73, Ed - KL7UW
"Kits made by KL7UW"
Dubus Mag Business e-mail:
dubususa at gmail.com
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