I Will Be Reckless.

TJExcalibur

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That sounds very optimistic.
I can only quote from those with more knowledge than I, and that is almost everyone when it comes to satellite setups.
Tried to upload but unable, web page not complete.

xxx.satellite-calculations.com/Fibo/fibo.htm
 

TJExcalibur

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I have Visiosat 120 antenna. The mirror only weights 13.4kg (against Channel Master's 10kg). But parameter-vise it as almost a copy of Channel Master- 1200x1300mm and 22.6* offset angle. Very solid dish, I must say.
Now you are getting me tempted again.......must admit it looks like a very nice solid dish.
 

Captain Jack

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Given the price differences between all these 1.2m dishes, a Channel Master wins hands down. Especially their abundant availability in 2nd hand market. From practical experience, a Fibo 120 just about has the edge over the CM but it's quite negligible.

The Fibo does look better, though!
 
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Now you are getting me tempted again.......must admit it looks like a very nice solid dish.
Too heavy. Gain diffs between equally sized (120cm) dishes is neglible.
Dual optics give better signal quality, yes, but the visiosat w. Dual optics is even heavier.
If you crave new gear, go for laminas on a stab120. Should work if mounted properly.
If you want to experiment, and are more budgetminded, find a cm120 w. Polarmount, and modify w. Arm and subreflector of your current fibo. @RimaNTSS can point to his thread where hes done something like that.
 

Channel Hopper

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If you want to experiment, and are more budgetminded, find a cm120 w. Polarmount, and modify w. Arm and subreflector of your current fibo. @RimaNTSS can point to his thread where hes done something like that.

That is already on the cards, though sticking a subreflector from another design is unlikely to improve on the original design, with the exception of the aperture, meaning a narrower feed will be needed.
 
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That is already on the cards, though sticking a subreflector from another design is unlikely to improve on the original design, with the exception of the aperture, meaning a narrower feed will be needed.
As I said, this is if OP is willing to experiment.

On a different note, as I seem to remember that the dual optics stuff was/is most often used for Rx/Tx configurations, where cross-polarisation separation was at a premium. @Channel Hopper: Can you confirm whether this mostly makes a difference in Tx, and that Rx does not benefit as much with a sub-reflector, or if Rx also gains enough to make it worth pursuing?
I know that the Fibos came with the dual-optics for most configurations, including Rx-only.
(And of course @RimaNTSS mini-Fuba :) )
But the Visiosat with dual reflector is almost always shown in an Rx/Tx configuration, so I wonder if it really makes enough difference for Rx applications on relatively small dishes for it to be worthwhile chasing after?
 

RimaNTSS

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By theory, dual-reflector antennas have ~10% better aperture efficiency, that means ~10% better performance of the system. And that is in Rx and Tx. That is theory, but, as we all know, practically it can be different. Performance of SAT-systems it is something what is hard to measure and compare.... IMHO.
 

Channel Hopper

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As I said, this is if OP is willing to experiment.

On a different note, as I seem to remember that the dual optics stuff was/is most often used for Rx/Tx configurations, where cross-polarisation separation was at a premium. @Channel Hopper: Can you confirm whether this mostly makes a difference in Tx, and that Rx does not benefit as much with a sub-reflector, or if Rx also gains enough to make it worth pursuing?
I know that the Fibos came with the dual-optics for most configurations, including Rx-only.
(And of course @RimaNTSS mini-Fuba :) )
But the Visiosat with dual reflector is almost always shown in an Rx/Tx configuration, so I wonder if it really makes enough difference for Rx applications on relatively small dishes for it to be worthwhile chasing after?


The advantage of gregorian/cassegrain designs is the improved cross polarisation isolation, so for receive/transmit application it does have an advantage (caveat co-pol systems).

The longer path to the feed from the primary reflector can also give a higher rejection from adjacent satellite and background noise since the feed is looking at a smaller part of space, though the latter is used more in transmit mode to improve isolation, to pass more stringent certification at higher frequencies. It will however offer a better downlink on a receive only system, but only on very close satellites where they have similar bouquet frequencies.

In a dual optics installation, all angles designed into the geometry, including the feed design need to be far better than the single reflector / LNBF combination, much like a quality magnifying glass when pitted against an average microscope.
 
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