Fibo 1.2m v Channel master 1.2m

Riverblue

Riverblue

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I was chatting to a guy the other day that was trying to sell his beaten up Fibo 1.2m dish and he reckoned that it had the performance of a 1.8m dish :rolleyes: Now I'm no expert but I know that when it comes to satellite dishes there is no substitute for size, so I cannot see how a Fibo can be that good! But it did get me thinking, I have a Channel Master 1.2m which I'm very happy with, but how does it compare with a Fibo 1.2m? How do the two heavyweights of the 1.2m department measure up against each other, which gives the most with a like for like install (if possible) the Channel Master 1.2m or the Fibo 1.2m? Are they both of similar size? What are the advantages of the "gregorian" dish over an offset dish, if any? I know there are members of this forum that have one or the other of these dishes, but what about those that have both, or have had both, what's your opinion or experience of these dishes? :)
 
I have the Fibo 1.2m dish. I would say it has the performance efficiency of 1.4m dish. It has a sub reflector which catches the signal from the main reflector refocusesand it before bouncing the signal into thelnb. Full details are below:
Offset antenna efficiency calculator
Antenna Beamwidth@11.7GHz1,45 degrees - 1,5 degrees theoretical
Antenna Offset18 degrees
Waveguide FlangeC120
Reflector typeGregorian offset - two reflectors
Antenna MaterialAluminium
Antenna surface & feedsupportCrom & epoxy
Polarmount+/-90 degrees
Weight11 kg
Elevation range30-75 degrees
Declination range30-75 degrees
Wind speed limit
Pipe for Polarmount/Fixed mount76mm X 5mm
Bolts on reflectorM8
Distance between bolts205x170
Suited LNBsInvacom C120 Single,Twin,Quad etc., MTI AP8-TW,Digistar SC-1
LNBs that does NOT fitDigistar TC-22,MTI AP82-TW,MTI-AP84-TW
 
The fibo is 1.4m tall and 1.2m across.
It is also said the 55cm Fibo performs like an 80cm.
 
Hi! I like this topic!
Before we start to compare different sat-systems, could we agree on methodology how to do measurements and then compare results with final goal to be able to say something like this: System A performs 10% better than system B!
Any ideas?
I have several offset, prime-focus and Gregory dishes and for long time wish to find formula how to compare their performance.
Last summer I did some measurements on 1,8m offset dish and then converted it to Gregorian type, and according to my way of thinking got up to 8% of improvement.
I only think I was calculated %% not the way they should be calculated.
Topic is here
 
Yes but the Fibo looks nicer IMO :D
 
Theoretical advantages for reception, of gregorian style dishes over offset dishes:
LNB overspill is more into the cold sky, instead of warm walls etc. (Depending on install location.)
No cross-polarisation degradation.
 
I think, theoretically and practically Fibo1,2m (not warped) will outperform CM1,2m (can not be warped). And this out-performance will be 5-10%.
But, at the same time, CM1,2m with properly designed and attached subreflector will perform not worse than Fibo 1,2m.
 
Riverblue said:
90cm = 110cm operating at 122.22%

55cm = 80cm operating at 145.45%

Sounds like speculation to me, or the larger dish is nowhere near as effective, probably the former.
Click to expand...

Well, you haven't done your maths correctly ;) You have to compare the area and not the diameter :)
 
BlindFaith said:
Well, you haven't done your maths correctly ;) You have to compare the area and not the diameter :)
Click to expand...
Even as a rough calculation (which it was) the figures would still be about the same as working out the area exactly and comparing them percentage wise . . . There would be a vast difference between "the claimed" performance of these dishes that doesn't equate when you scale them up. In other words something is not right with these claims!

Doing the maths properly . . area = π(length a/2)(length b/2)
90cm (0.69979m²) = 110cm (0.88844m²) Triax td110 = 126.96%

55cm (0.25918m²) = 8ocm (0.42883m²) Technomate TM80cm = 165.46%
 
Have to dissapoint some people , made a test against my Fibo 120 years ago wenn Laminas came with his first OFC 1200
Both equipt with BU single lnb , no difference between them at Nilesat .
A member at a dutch board claims to have a better signal on his no-name 120 offset dish , he is living ± 50 km more south to me .
 
@Riverblue, you don't have to take the length into account, cos from the satellite an offset dish is seen as a circle.

It's only the width that counts. The gain is proportional to the effective area of the dish. Comparing 110cm to 90cm yields a theoretical gain of -> 20log(110/90)= 1,74dB and 80cm /55cm -> 3,25dB

@hvdh has described the advantage of a gregorian dish correctly. The effective area is increased due to a more precise illumination. But don't believe in wonders ;)
 
@Trust1, IMHO it's not that easy to compare the dishes. A gregorian dish normally comes with a matched feedhorn which could give an additional advantage compared to a standard offset-LNBF.
 
I have made practical comparisons between a 1.2m Channel Master and a Fibo. Bottom line - the Fibo is slightly better than the CM but only just. And my 1.5m Gibby walks all over the Fibo. Search for my thread title 'Fibo project' and it will be on the 4th or 5th page. Can't do it here as I am in bed on my phone.

It's a good, efficient dish but it doesn't perform magic tricks.
 
And, as I mentioned before to compare dishes you have to have
RimaNTSS said:
Fibo1,2m (not warped)
Click to expand...
But, unfortunately, after so many years and stormy days it is not so easy to find Fibo in ideal shape (except Fibo55, cuz they seem unbreakable).
 
BlindFaith said:
@Riverblue, you don't have to take the length into account, cos from the satellite an offset dish is seen as a circle.

It's only the width that counts. The gain is proportional to the effective area of the dish. Comparing 110cm to 90cm yields a theoretical gain of -> 20log(110/90)= 1,74dB and 80cm /55cm -> 3,25dB

@hvdh has described the advantage of a gregorian dish correctly. The effective area is increased due to a more precise illumination. But don't believe in wonders ;)
Click to expand...
Sorry to be a thicko but could you explain your calc to me please, how do you get dB? What is 20log?
Okay, my methods may be wrong but even so your calcs still show a disproportionate amount of gain re difference in size, if I'm understanding them correctly. Which still suggests that one of these claims is wildly inaccurate, or am I interpreting this all wrong?:confused
 
20log is a logarithmic scale - can be found on most ' scientific' calculators. Been a long time since I had to do those types of calculations!
 
Having just "googled" for more info on logarithmic calcs and non linear scales I can honestly say that my head hurts, it must be all that extra gain in knowledge! :-wow Unfortunately it's about as clear as mud :confused
 
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