Another one for the Arsenal: Gibertini OP 125 L

[archive10]

Used the spring weather (10C) to give the dish a test-drive.
Equipped it with an Inverto BUQ (nearest LNB when I went looking).
Initially aligned it at 19.2E. Fairly easy to find, but SNR not hugely impressive - but reasonable.
Tried it then briefly at 28.2E, but again was not very impressed with the results.
Ran out of play-time, but will retry on 28.2E soon.
(If it works on a CM120, it should on the OP125 as well!)

 

[Trust]

First look like this and if it's worth, before my hopes, the OP130 has a defect, the signal is not focused 100% on the LNB and you can move this drawing a circle 10cm if signal loss.
I have more antenna signal 90cm (98x90cm) beam pointing to 28'2ºE UK with the OP130 (138x130cm) from Madrid (Spain).

PS:

Probably caused by wrong feedarm assembling (upside down)

 

[archive10]

Probably caused by wrong feedarm assembling (upside down)

Good point. So I went and checked, and the feedarms on mine is not like the ones in the picture.
Mine are entirely flat in the horizontal plane, so mounting them upside down makes no difference...
Although each arm is made from square tubing, it is not possible to mount them turned 90 degrees, as they would never meet at the LNB end.

So I don't think that they are the cause at this stage...

Edit: Just checked @Johns pics here Just Sharing This - 1.2 Precision / Octagon lnbf mod, and the arms on his are just like the ones on mine (ie flat).

 

[Tururu]

View attachment 101175
Probably caused by wrong feedarm assembling (upside down)

.

The arms of the LNB are not mounted around the original antenna instructions.
If I dismantle the LNB, I can move it with a 10cm radius around the LNB bracket (maximum signal) and I have the same signal.
If I put the LNB behind the stand, I have a better signal.
It is clear that the signal is concentrated behind the LNB.
I need longer arms or I convert the antenna into a Cassegrain.
These are not the arms of the antenna that I have (original, sealed in box).
Tests from Madrid pointing to the Astra at 28'2ºThis 10714H (very critical signal).
With the motorized antenna of 90cm without problems.
Gibertini_5.jpg


An antenista friend I set a similar antenna of 130cm this week and I asked that it measured the arms of the stand when observing that they are longer than mine, its arms are of 95cm.
The antenna arms I have OP130.- 77'5cm
@ ST1 if you can measure the arm length of the OP125? We will leave doubts
Giber_4a.jpg

----------------
No estan montados alreves los brazos del LNB, segun instrucciones originales de la antena.
Si desmonto el LNB, lo puedo mover con un radio de 10cm alrededor del soporte del LNB (maxima señal) y tengo la misma señal.
Si pongo el LNB detras del soporte, tengo mejor señal.
Esta claro que la señal se concentra detras del LNB.
Necesito unos brazos mas largos o convierto la antena en una Cassegrain.
Estos no son los brazos de la antena que tengo (original, precintada en caja).
Pruebas desde Madrid apuntando al Astra a 28'2ºEste 10714H (muy critica la señal).
Con la antena motorizada de 90cm sin problemas.
Gibertini_5.jpg

Un amigo antenista ajusto una antena similar de 130cm esta semana y le pedi que midiera los brazos del soporte al observar que son mas largos que los mios, sus brazos son de 95cm.
Los brazos de la antena que tengo OP130.- 77'5cm
@ST1 si puedes medir la longitud del brazo de la OP125? saldremos de dudas.
Giber_4a.jpg

My name is my friend, bring me some support arms (95cm), I'll already comment.
Me llamo mi amigo, me trae unos brazos del soporte (95cm), ya comentare.
Thanks for the info/Gracias por la informacion.

 

[John]

... Just wondering if this helps you

 

[archive10]

An antenista friend I set a similar antenna of 130cm this week and I asked that it measured the arms of the stand when observing that they are longer than mine, its arms are of 95cm.
The antenna arms I have OP130.- 77'5cm
@ ST1 if you can measure the arm length of the OP125? We will leave doubts

I just went and measured, and the distance from the bottom-most bolt holding the feed-arms to the plane of the LNB holder is 95,0 cm.
The distance from the centre of the dish to the plane of the LNB holder is 97,5 cm (just like @John 's)



Also, your feed-arms has a clear angle just before the LNB, as you indicate with a green line on the picture.
I have none of that, neither does john.

I think you have the wrong set of feed-arms...

 

[Trust]

quote [These are not the arms of the antenna that I have (original, sealed in box).]
How do they look like and why dont you use them ???
When the lnb is pointed higher in the dish , the focal lenght is longer , that will give you more signal .
But you have to change the elevation of the dish also .
Can you tell me at which elevation is that dish when pointed to 28.2º E

 

[Trust]

Good point. So I went and checked, and the feedarms on mine is not like the ones in the picture.
Mine are entirely flat in the horizontal plane, so mounting them upside down makes no difference...
Although each arm is made from square tubing, it is not possible to mount them turned 90 degrees, as they would never meet at the LNB end.

So I don't think that they are the cause at this stage...

Edit: Just checked @Johns pics here Just Sharing This - 1.2 Precision / Octagon lnbf mod, and the arms on his are just like the ones on mine (ie flat).

Upside down means 180º , I'm almost sure that will fit .

 

[archive10]

Upside down means 180º , I'm almost sure that will fit .

Yes, but as the feedarms are entirely flat, turning them 180º will make no difference...

 

[Trust]

Yes, but as the feedarms are entirely flat, turning them 180º will make no difference...

I'm talking about the arms of @Tururu

 

[archive10]

I'm talking about the arms of @Tururu

Then why are you quoting me? ;)

 

[Trust]

Then why are you quoting me? ;)

I dont think I did

 

[archive10]

I dont think I did

But you did...



I can see that you are quoting @Tururu above in the first post, but I do not quite see how that post comes into this thread??

But let's not digress...
The point is - Tururu has the wrong feed-arms, whereas I seem to have the right ones.
But I still do not have proper reception of 28.5E!
I will swap the Gib125 for a CM120 very soon to see what the reception *could* be like...

 

[Tururu]

@ st1
At the beginning, I ask you to come to sack in the post.
In the photo with the measurements you indicate and other photos, you have it with the antenna cable at 6 (imaginary relog), it would have to be almost at 8 (28.5E), At 7 is for 19'2ºE +/-.
I'm referring to the adjustment of lnb polarization, it's wrong, looking at the antenna in front.
Do not forget..
What size of antenna do the neighbors have in Nordsjælland, Denmark?
-------------------------
@st1
De entrada te pido perdor por entrar a saco en el post.
En la foto con las medidas que indicas y otras fotos, lo tienes con el cable de antena a las 6 (relog imaginario), tendria que estar casi a las 8 (28.5E), a las 7 es para 19'2ºE +/-.
Me refiero al adjustment of lnb polarization, esta mal, mirando la antena de frente.
No olvides..
¿Qué tamaño de antena tienen los vecinos en Nordsjælland, Dinamarca?

Thanks for the pictures/Gracias por las fotos.
Of course, the LNB brackets are not from this OP130 antenna.
Tomorrow, if time permits, change them.
The new stand is the same as the one you have ST1 95cm, Jhon has the same, with the new LNB support and the carton of the disk

100% plan.
Soporte_95cm_OP125.jpg


Photo so you can see the difference, the LNB is 2cm higher, than cold, freezing the fog.
Soporte_95cm_OP130a.jpg

----------------------------
Esta claro, los soportes/tirantes del LNB no son de esta antena OP130.
Mañana si el tiempo lo permite, los cambio.
El nuevo soporte es igual al que tienes ST1 95cm, Jhon tiene el mismo, con el nuevo soporte LNB y la caja de carton del disco
Plano 100%.
Soporte_95cm_OP125.jpg

Foto para que se vea la diferencia, el LNB queda 2cm mas alto, que frio, congelandose la niebla.
Soporte_95cm_OP130a.jpg


@ Trust1
It touches change orientation (Astra to 19'2ºE currently) and also elevation by the new position of the LNB.
The photo tricks the angle, points higher the LNB.
The support of the plate has no elevation reference, I have marked the position for 19'2°East and 28'2°East.
I will have to look tomorrow, I think if you have screen printing elvacion, total memory failure.
-------------
Toca cambiar orientacion (Astra a 19'2ºE actualmente) y tambien elevacion por la nueva posicion del LNB.
La foto engaña por el angulo, apunta mas alto el LNB.
El soporte del plato no tiene referencia de elevacion, tengo marcada la posicion para 19'2ºEste y 28'2ºEste.
Tendre que mirar mañana, pienso que si tiene serigrafia de elvacion, fallo total de memoria.

 

[RimaNTSS]

Gentlemen! I do not have such a dish, so I can not contribute, but..... would not that be easier to measure that beast, calculate its main parameters (position of the Focal point, offset angle, opening angle, position of the "la point G" ), afterwards place LNB in such a way that its Phase center is co-located with antenna's Focal point and LNB is pointed properly?

 

[archive10]

Gentlemen! I do not have such a dish, so I can not contribute, but..... would not that be easier to measure that beast, calculate its main parameters (position of the Focal point, offset angle, opening angle, position of the "la point G" ), afterwards place LNB in such a way that its Phase center is co-located with antenna's Focal point and LNB is pointed properly?

Ah, there you are RimaNTSS... ;)

 

[archive10]

@ st1
In the photo with the measurements you indicate and other photos, you have it with the antenna cable at 6 (imaginary relog), it would have to be almost at 8 (28.5E), At 7 is for 19'2ºE +/-.
I'm referring to the adjustment of lnb polarization, it's wrong, looking at the antenna in front.
Do not forget..
What size of antenna do the neighbors have in Nordsjælland, Denmark?

The picture of the Gibertini 125 was taken when the dish was aligned at 19.2E.
I am further east than you (13E is due south of me), so I need less skew.
But 28.2E does need more skewing than what's in the picture. In your terms, it's about 6:30 for 28.2E ;)

Regarding size: 180cm is good and has rain margin. reception of 28.xE is possible on a good 120 cm antenna, my CM120 works great.
This is why I was a bit surprised that I couldn't get better signal on the Gibertini 125 (which is a 121cm in reality) the other day.
(I have even received 28.xE on a Channel Master 100 - but the signal fades away too much in the late afternoon.)

The antenna size only works for eastern Denmark (Nordsjælland), because of a side-lobe centered on southern Sweden.
If you go further west in Denmark, you need much bigger antennas, and there's even a null straight down the middle of the country.

 

[timo_w2s]

My Gibertini 125 arms are straight too, but now I'm curious so I'll take a closer look at measurements when I can get to the dish.

 

[archive10]

Tried it then briefly at 28.2E, but again was not very impressed with the results.
Ran out of play-time, but will retry on 28.2E soon.

Spring has been here for a few days, so the itch was getting unbearable...
I needed to do something dishy!

So I snook out after dinner to fiddle with the Gib 125 in the evening light.
I was puzzled by the really poor 28.5 performance from December - it should be roughly as good as the CM120.
But even after much adjustment in Dec, I couldn't even make the meter lock unto 10730V.

My suspicion was directed to a whisk of branches of a Neighbour's bush (and to pre-empt several member's comments - no, the garden type bush), that could be in the beam of the reflector.



I therefore removed dish and ballast slabs, and moved the tripod some meters.



Much better - found 28.5 and 2E, and finally got at lock on the meter.
After a lot adjusting of bolts, I had to resort to mangling and wrestling the steel of the mount and the reflector itself to maximise the signal.

Maybe it's the (slight) rustiness of the adjustment bolts, maybe they would work better if lubricated, but I found especially the elevation adjustment not to be quite as smooth as I would like.
In fact, the best mount I have tried so far (for smaller dishes) in this respect is the Channel Master Az/El ones for the 100 & 120 cm dishes.

In any case, the signal now peaks at 71 dBuV and a C/N of 7.7 dB with an Inverto Black Ultra Quad.
Quite happy with that - it is most likely the effect of the branches that hampered the reception in December.



Finally went inside and compared the performance with that of the CM180.
The Gib 125 is (only) 3 dBuV less than the CM180 - so this is on par with expectations! Yeay!
(But note that the CM180 reading is through a multi-switch, so disregard the power measure.)



The other thing I tried was to find how the LNB should fit in the LNB holder of the Gib.
Experimentation showed that the long neck of the IBUQ was of no benefit here.
The best positioning was to have the feed-horn as far away from the dish as the LNB holder allowed, and then just a little back.
I interpret this as the Gib is happy and good with normal- to short-neck LNBs. No Channel Master BS here.



Next steps on the Gib is probably to loosen the screws on the back mount, and see of the same warping of the dish that @John experienced is also in this dish. But that'll be another spring day...

 

[Captain Jack]

Sleep is for the weak!