New gregorian dish, fibo. missing funnel... how to mount universal lnb?

[MarsBar]

Okay, I picked this up locally as I allready have an identical dish, approx. 80cm. (BBC dropout in heavy rain in Rogaland, Norway)

The new one is 1m.

Fibo Gregorian Dual Reflector Antenna Information

Fibo Gregorian Dual Reflector Antenna Information

www.satellite-calculations.com

Unfortunately, the owner had replaced the funnel and original LNB with an universal LNB... Sounds cracy, but he said it worked perfectly. He installed it with a bracket made of wood... poorly made and rotten so I discarded it.

My question is now:

1)

Where is the exact location of the universal LNB? At the drawings it shows the focal line is not paralell to the aluminium beam holding the sub reflector. So the universal LNB should be tilted a bit accoding to the line on the drawing...

I am not sure of the distance either, the previous owner simply but the universal LNB by the screw hole for the original LNB bracket (!)

As mentioned I allready have a working dish, where I spliced in a universal LNB in line with the big funnel after the magnetic polarisator (not used).
Se other post for that picture.

I guess I could align the satellite dish, then fine tune the LNB on a strong sattelite, like hotbird to find the sweet spot of the LNB.

Another solution is to look for similar antenna and get hold of the missing funnel... maybe som small antennas for sale, I assume they only changed the main reflector for the different models.

It's gonna be a challenge to make a bracket of aluminium, but I have plenty of aluminum profiles.

2)

I have an old canal digital LNB, but it has 3 outputs. One output mentions 4 frequencies, while the two others are for some other service (?) Will get a picture later. Anyone know what kind of LNB is? Can it be used as an universal LNB by just using the one plug?

 

[Channel Hopper]

Did Fibo manufacture a 1m gregorian ?

 

[MarsBar]

Maybe I measured wrong, because it's taller than wider. This must be the biggest dish

 

[nelson_b]

Maybe I measured wrong, because it's taller than wider. This must be the biggest dish

Hi -
The Fibo dish is measured across the width .... so its a 90 c. m. ... the motor assembly you have there is also the one for a Fibo 90 ... i will take a pic of the arm+ feed later ... from the one i have stored here.
Cheers.

 

[nelson_b]

Hi

I,v enclosed a picture of the feed , to show angle and height ... but to use a normal universal l.n.b - i think will be trial and error to find the best spot . I have no spare parts for Fibo dishes - But @RimaNTSS may have .. or have some good suggestions - when he comes online.

Cheers.

 

[TJExcalibur]

Try here. They also parts not shown.

Masterfocus-Antennas

Wir sind Spezialisten im Bereich Kopfstellen, Antennen, Verteiltechnik, Antennenheizungen, Multischalter, Optische Übertragungstechnik, BK-Verstärker, MMDS, LNB, Receiver, Satellitentechnik, digital und analog. Wir liefern, Grundig, Astro, Polytron, Hirschmann, Masterfocus, Kathrein, Blankom...

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[RimaNTSS]

Interesting topic and nice antenna!

It's gonna be a challenge to make a bracket of aluminium, but I have plenty of aluminum profiles.

If you can not make it perfect make it adjustable. That is one holder I've made couple of days ago. You, of course, can come with another solution out of aluminum, plastic or even wood.
If you do not have original Fibo feedhorn I would suggest to:
- remove the SUB and install universal LNB in antenna's focal point and aim LNB to antenna's G-spot;
- catch your due-south satellite to get maximum signal;
- without moving the dish, remove the LNB and install the SUB.
- install LNB in the SUB's secondary focal point to get maximum signal;
- enjoy perfectly tuned Gregorian type antenna and perfect reception performance.

It is too late ATM. I will come back tomorrow with data about antenna's offset angle, location of focal point and LNB's aiming point.

 

[Channel Hopper]

The focal point of the antenna will be beyond the end of the feedarm in single reflector mode.

 

[scopus]

Did Fibo manufacture a 1m gregorian ?

90cm

 

[RimaNTSS]

@MarsBar on the attached picture you can see some data of your antenna. I used picture of Fibo55, but data is about Fibo90. Focal point if the main reflector is located somewhere in the red circle. So, for the first step you need to place universal LNB in such a way that it's phase center co-located with antenna's focal point. Offset angle of Fibo 90 is 24,6*. When you point your antenna to due-south satellite you can measure leaning of the reflector and from data you get it is possible to find out whether you have LNB in the right position.

 

[MarsBar]

Thanks for info RIMA!

When you look at the original funnel, the funnel ends in a round circle that leads the signal in a round pipe pass the magnetic polarizer. (The magnetic polarizer was simply a copper coil wound round the pipe with some DC current)

Where is the focal point originally? Inside the funnel at the end, middle, or by the funnel cap?

If the focal point is in the end of the original funnel, the focal point, I assume, should be at the end of the funnel of an universal LNB.

The strange part is that the funnel originally was quite big, I have never seen such a funnel later. Maybe aestetic purposes? The antenna won an design award once introduced for good design here in Norway.

(I have an original antenna setup 100% original I may take measurements on, so I have the measurements.

I am currently searching the net for antennas for sale, because if a smaller diametre one is for sale the funnel will be the same I assume.
This will be a winter project, but I am starting now to collect and make parts in my garage.

 

[RimaNTSS]

Second focal point of the SUB is located well inside the feedhorn, approximately where I put the red star.

 

[MarsBar]

One last question for now, ideally, where should the focal point hit an universal LNB? By the CAP entrance to the funnel, or inside the funnel like 1cm from the entrance cap? Then I have something to start with, LNB can be re-adjusted for best signal using a analogue sat meter later on, but I have to start somewhere.

 

[RimaNTSS]

This is the answer given by Inverto representative. That was about Inverto Black Ultra LNB.

 

[MarsBar]

I found this old LNB I am thinking of using on the dish.
It's from a canal digital subscription setup. Will this work 100% as a universal LNB if I use the right socket? The two to the right are marked "Legacy". What does this mean?

 

[ozumo]

Legacy is usually the standard universal LNB outputs.

 

[jeallen01]

I found this old LNB I am thinking of using on the dish.
It's from a canal digital subscription setup. Will this work 100% as a universal LNB if I use the right socket? The two to the right are marked "Legacy". What does this mean?

Google "fr8-q52" as there is some information on this LNB on the web, but I didn't see anything about the 2 "Legacy" o/ps - could they be either 2x conventional "Universal" ports, or 1 Vertical o/p & one Horizontal o/p (I suspect the first??)?

 

[MarsBar]

I had to drill out the gear from the aluminum base, had a spare from the locking kit 30 years ago in a drawer. All greased up now. Made an universal adjustable arm for the LNB in aluminum and stainless steel screws. I will move this bracket to an allready installed working similar dish in order to test where the focus point is using a meter, then lock the bolt tight. Hopefully this will work, this will enable me to change LNBs without modification.

 

[MarsBar]

Okay, swapped my home made bracket into a working setup today. The height of the LNB is critical, distance from 2nd sub reflector not so critical on the mm. Have taken note of measurements in case bracket moves... distance was approx. 100mm from reflector and height approx. 90mm from boom to LNB feedhorn bottom tip. LNB should tilt 3 deg backwards.

Test showed pretty much the same signal strength, but 2 percent lover strength with my bracket. Maybe it can be fine tuned for the last 2 percent?

I fined tuned the test dish, it had sagged a bit to I adjusted it a bit up, then tighening the bolts. I used a cheap analogue moving pin meter with beeping sound.

So, it is proven that it will indeed work. I think a signal loss of 2 percent is within reason?

 

[MarsBar]

It looks like both dishes are 90x100cm.

Here are the measurements:

Distance: 81mm

Height from beam top to center lnb: 102mm

LNB approx 3 deg backwards.

Current offset dish: 95x85cm

New dish, dub reflector: 90x100.