African Satellite World and Sat Gear

Lunsat2 · Jan 25, 2019

freq said:
Sorry I didn't get it..

Think in three dimension.

This is the problem. I think you need to understand what I am saying.

1. I am not disputing that an offset dish of say 120cm has more gain than a prime focus dish of 120cm.

1. I am disputing your thesis that merely increasing the tilt/ offset angle of the dish with dimensions held constant increases the illuminated surface and hence the signal gain of a dish. I hold that the light beam on the Wall example you gave is erroneous because a light imprint on a wall grows bigger when you change the angle of the light beam but a physical dish doesn't change its size when you slant it.

3. The other explanations which you are now bringing out are actually more sensible alternative explanations for the higher signal gain of offset dishes over prime focus dishes of the same size than the wall illumination crap you are defending: An offset dish is taller hence more surface area- I agree; an offset dish minimises ground noise- I agree; an offset dish avoids lnb obstruction of signal- I agree. On these I am in total agreement with you and I give you a standing oversion.

RankSat · Jan 25, 2019

freq said:
I've researched on what makes offset dishes better than pf dishes and come to think and read about it;

Think of someone shinning a torch at a wall at night... There are two ways you can do it..

One; point it directly and perpendicularly to the wall... You'll find a relatively small Perfectly Round area of illumination... If the torch is your satellite, light is your radio signal from the satellite and the wall is your dish pointing directly at the satellite (like a pf dish does). Your dish will gather relatively small amount of radio waves while pointed directly at the sat due to the small rounded area of illumination..

Scenario Two; You are pointing your torch at the wall but now at an angle say 30 degrees to the wall. You'll see the area of illumination on the wall is larger and Oval. (Like an offset dish)... So if the torch is your satellite radiating radio waves as light in this case, placing an oval dish to look at it at an angle will maximize the area of illumination, thus gathering more "light". More collection means better performance.

Of course in real world we cannot make the torch which represents our satellite to look at our dish or "wall" at an angle. What we do is tilt our "wall" or dish to look at the "torch" or satellite at an angle Called the offset angle.

Thus the birth of offset dishes which should perform better than their pf counterparts.

Perfect explanation!!

freq · Jan 25, 2019

Lunsat2 said:
the wall illumination crap you are defending: .

No need to be abusive and vulgar.

lets argue out our points in a civilized manner backed up with practical examples like scientists...

And with that I withdraw from this argument.

Every man has a right to believe in what he believes in ~ Bob Marley [Song: Zimbabwe]

X-PONDER · Jan 25, 2019

Perception

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freq · Jan 25, 2019

RankSat said:
Perfect explanation!!

Thank you

Eutelsat · Jan 25, 2019

kungu1 said:
My current location is Limuru, Kenya.

I specialize in fringe satellite reception.

Some of the satellites i have tracked of late in Kenya Include:

Measat 3/3a @91.5°E C band on 2.4 meter prime focus,
Thaicom 5 @78.5°E C band on 1.8 meter prime focus
Apstar-7 @76.5°E C band on I.8 meter prime focus
ABS-1 @75.0°E C band on 2.4 meter prime focus
Intelsat 7/10 @68.5°E C/KU band on 2.4 meter prime focus and 90cm offset
Intelsat 17 @66.0°E C/Ku band on 2.4 meter prime focus and 90 cm offset
Intelsat 906 @64.2°E C band on 1.8 meter offset
Intelsat 902 @62.0°E C band on 2.4 meter prime focus
Intelsat 904 @60.0°E C band on 2.4 meter prime focus
NSS-12 @57.0°E C/Ku band on 1.8 meter prime focus and 90cm offset
Yahsat 1A @52.5°E Ku band on 1.5 meter offset
Intelsat 26 @ 50° East C band on 1.8 meter prime focus
Paksat 1R @38.0°E C band on 1.8 Prime focus
Eutelsat 36A/36B @36.0°E Ku band on 90cm offset
Intelsat New Dawn @ 32.9°E Ku band on 90cm offset
BADR 5/6 @26.0°E on 2.4 meter offset
Amos 5 @17.0°E C/Ku band on 1.8 meter prime focus and 90cm offset
Eutelsat 16A @16.0°E Ku band on 90cm offset
Eutelsat 7A @7.0°E Ku band on 90cm offset plus 1.5 meter for fringe satellite recption of Eutelsat 7A Europe B footpring
Astra 4A 4.8°E Ku band 90cm offset
Rascom-QAF1R @2.8°E C/Ku band on 1.8 meter prime focus and 90cm offset
Intelsat 10-02 @1.0°W C band on 1.8 meter prime focus
Eutelsat 5 West A @5.0°W C abnd on 1.8 meter prime focus
Eutelsat-7WA and Nile201 @7.0°W on 1.5 meter offset
SES-4 @22.0°W on 90cm offset
Plus more satellites,

Eutelsat · Jan 25, 2019

Hi Kungu, Please advice the latest FTA within the Sub-Sahara region that brings sports, news , docs etc

Mfetra · Jan 25, 2019

freq said:
I've researched on what makes offset dishes better than pf dishes and come to think and read about it;

Think of someone shinning a torch at a wall at night... There are two ways you can do it..

One; point it directly and perpendicularly to the wall... You'll find a relatively small Perfectly Round area of illumination... If the torch is your satellite, light is your radio signal from the satellite and the wall is your dish pointing directly at the satellite (like a pf dish does). Your dish will gather relatively small amount of radio waves while pointed directly at the sat due to the small rounded area of illumination..

Scenario Two; You are pointing your torch at the wall but now at an angle say 30 degrees to the wall. You'll see the area of illumination on the wall is larger and Oval. (Like an offset dish)... So if the torch is your satellite radiating radio waves as light in this case, placing an oval dish to look at it at an angle will maximize the area of illumination, thus gathering more "light". More collection means better performance.

Of course in real world we cannot make the torch which represents our satellite to look at our dish or "wall" at an angle. What we do is tilt our "wall" or dish to look at the "torch" or satellite at an angle Called the offset angle.

Thus the birth of offset dishes which should perform better than their pf counterparts.

Well put.Tthe only hindrance is that offset and pf do not compare price wise

X-PONDER · Jan 25, 2019

Friendly fire.

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freq · Jan 26, 2019

Mfetra said:
Well put.Tthe only hindrance is that offset and pf do not compare price wise

That's mainly due to transportation costs...

Offsets often come as one huge thing or a huge thing separated in two thus occupying more cubic feet while shipping..

And you still have to fabricate some parts when it lands.

Let Love Reign · Jan 26, 2019

This debate always recur and until today, there is no cemented findings that every one agrees of! By the way, its part of the scientific principles that the research should leave room for others to challenge it so well mannered presentation is what's needed.

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nahdy · Jan 26, 2019

PF+OS combined..

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Let Love Reign · Jan 26, 2019

You guys remember, a month ago, I was here requesting a piece of advice when I wanted to go 2.4!
That is after doing a three months google research! and never came to a conclusion! Among the guys I usually salute are the so called US Satellite guys, as these guys have scientific equipments enough to check and balance but they also never came to consensus!
But one thing they both agreed!

That PF of 2.4 will never outperform offset of the same size in KUband.
And Offset dish of that same size will never outperform PF dish in CBand.
This also was indicated by if I'm correct GIDEN, and/or VICWA.

That being said
The other guys! Not sure if Asian forum or what, they had somewhat the above stand
although they said An offset could as well do both, KUand Cband better than PF could do both ku and Cband given precision is taken to point I.e equivalent CBAND LNB GAIN for Offset, should be the same with that Ku lnb gain for Cband, given that other factors too are the same.

2.4 Prime focus what will be its equivalence in Offset dish for Ku purposes?

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freq · Jan 26, 2019

Let Love Reign said:
You guys remember, a month ago, I was here requesting a piece of advice when I wanted to go 2.4!
That is after doing a three months google research! and never came to a conclusion! Among the guys I usually salute are the so called US Satellite guys, as these guys have scientific equipments enough to check and balance but they also never came to consensus!
But one thing they both agreed!

That PF of 2.4 will never outperform offset of the same size in KUband.
And Offset dish of that same size will never outperform PF dish in CBand.
This also was indicated by if I'm correct GIDEN, and/or VICWA.

That being said
The other guys! Not sure if Asian forum or what, they had somewhat the above stand
although they said An offset could as well do both, KUand Cband better than PF could do both ku and Cband given precision is taken to point I.e equivalent CBAND LNB GAIN for Offset, should be the same with that Ku lnb gain for Cband, given that other factors too are the same.

2.4 Prime focus what will be its equivalence in Offset dish for Ku purposes?

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Ok look at it this way..

Originally in the 70s Dishes came in the form of prime focus....

Then as technology and research improved, offset dishes were released as an improved product.

So offset must be better than pf in some way.

Now the actual factors that make or made offsets better were and are still patented trade secrets... We can only speculate about them...

X-PONDER · Jan 26, 2019

Ku lnb to offset.
Ku lnb for prime focus for cband dish.aka bud.
The usual Ku lnb is not designed to view a wide surface,so using it on a prime focus dish will result in some signal loss.(lnb designed to view a small surface) As the lnb is not viewing the whole dish.Ku band lnb for prime focus is just as effective ,as it is designed to view a large surface. The results are the same for off set and prime focus dish if the correct lnb is used.The difference is signal can be 1 PC,based on the arm design of the dishes.

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X-PONDER · Jan 26, 2019

Simple test
Use your Fuji Ku lnb for prime focus on a 90/100 cm dish and note the signal level.
Repeat the same with the usual Ku lnb and note the signal level.
The usual common Ku lnb performed better than the Fuji Ku prime focus.

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X-PONDER · Jan 26, 2019

Did that on Bud ,180 cm @ Badr the Fuji Ku prime focus was tops, difference was 7 percent.

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GIDEN · Jan 27, 2019

Munyaga said:
GIDEN tokea....

Thanks Munyaga , there are several versions of Openbox V8 original and copy.

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GIDEN · Jan 27, 2019

freq said:
I've researched on what makes offset dishes better than pf dishes and come to think and read about it;

Think of someone shinning a torch at a wall at night... There are two ways you can do it..

One; point it directly and perpendicularly to the wall... You'll find a relatively small Perfectly Round area of illumination... If the torch is your satellite, light is your radio signal from the satellite and the wall is your dish pointing directly at the satellite (like a pf dish does). Your dish will gather relatively small amount of radio waves while pointed directly at the sat due to the small rounded area of illumination..

Scenario Two; You are pointing your torch at the wall but now at an angle say 30 degrees to the wall. You'll see the area of illumination on the wall is larger and Oval. (Like an offset dish)... So if the torch is your satellite radiating radio waves as light in this case, placing an oval dish to look at it at an angle will maximize the area of illumination, thus gathering more "light". More collection means better performance.

Of course in real world we cannot make the torch which represents our satellite to look at our dish or "wall" at an angle. What we do is tilt our "wall" or dish to look at the "torch" or satellite at an angle Called the offset angle.

Thus the birth of offset dishes which should perform better than their pf counterparts.

Actually my friend in addition to your theory the fact that makes offset better perfomers is
1. They consist of a 1-4 petals for very large offset dishes, thus nil or very low signal leakage due to gaps on petal joints or chances of warping due to incorrect assembly (errors).
2. Placement of feedhorn/the lnbf on offset dishes is placed at an offset angle ie away from middle like in pf, which casts a shadow nearly as large as the signal beam. On offset it doesn't cast a shadow.

Mind you the dish is the one that receives and reflects the signal to the lnb. Its a reflector. How perfect the shape is determines how much of reflected signal is aimed at the lnb. A slightly warped offset or with wrong focal length loses more signal than a pf.

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freq · Jan 27, 2019

GIDEN said:
Actually my friend in addition to your theory the fact that makes offset better perfomers is
1. They consist of a 1-4 petals for very large offset dishes, thus nil or very low signal leakage due to gaps on petal joints or chances of warping due to incorrect assembly (errors).
2. Placement of feedhorn/the lnbf on offset dishes is placed at an offset angle ie away from middle like in pf, which casts a shadow nearly as large as the signal beam. On offset it doesn't cast a shadow.

Mind you the dish is the one that receives and reflects the signal to the lnb. Its a reflector. How perfect the shape is determines how much of reflected signal is aimed at the lnb. A slightly warped offset or with wrong focal length loses more signal than a pf.

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Yeah. I mentioned all those factors at a later post.

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