Tests of 120cm antennas

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Repeated CM120 tests today. 2 measurements: with original CM LNB holder and with self-made one.
How I did it: installed original CM LNB holder and tuned antenna and LNB as perfectly as I could to 7,3*W , then scanned all 44 available transponders. Then, within 15-25 minutes (weather conditions did not change) installed self-made LNB holder, tuned antenna and LNB again and scanned same 44 transponders. Data analysis shows that I got increase of performance at about 5%, which is not bad IMHO.
Question: Can anybody of you receive 11661 V 27500 2/3, if yes, what signal level is?
View attachment 78829 View attachment 78830
Interesting results.
I am curious what instrument you are using to make the list; it seems practical to use the same...
 

RimaNTSS

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I use script for Enigma2 friend of mine made. I think I shared this script with instructions for it use some time ago. Search forum for keyword zap_to_every_transponder
 

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Question: Can anybody of you receive 11661 V 27500 2/3, if yes, what signal level is?
Just about on the 1.5m dish - breaking up badly. Looks like a NW African beam?

1_0_1_4_2A94_55E_DCA0000_0_0_0.jpg
 

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Not a hint of that transponder here in the north west u.k. using 1.8m cm
i can lock some of the stronger ones on you list though -- RimaTSS :)
 

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Hi! Continuing playing with this "toy" I've decided to do real measurements of CM120, and this is to continue proving that antenna's manufacturer made feedarms and LNB holder which are not holding LNB in proper position. For that purpose, on real CM120 antenna I am going to measure:
- distance A-F
- distance B-F
- position of the point G (aiming point of the LN:cool:
- angle between lines F-G and A-B

On the drawing I made is how everything should be :rolleyes:
I made drawing pretending dish is pointed at the satellite with elevation 30*.
ParabolaCM120cm (Large).jpg
 

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RimaNTSS

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I put strings to measure distances A-F and B-F IMG_20150531_172054 (Large).jpg IMG_20150531_175905 (Large).jpg . Got numbers 1225 and 712mm, not so bad, taking into account that calculated distances are 1220 and 720mm. Means that LNB is hold by original LNB holder only about 10mm (pink line) away from proper Focal point ScreenHunter_346 May. 31 18.17.jpg . Made one assumption: When LNB is inside the holder- it's Phase Center is about 25mm from the edge of the holder IMG_20150531_172927 (Large).jpg .

Next action will be angle-measurements.
 

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Put antenna on the floor and collected all tools I will need. Do I miss something?? O, yes, of course, I forgot about the pencil and tape. :rolleyes:
 

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Tururu

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By living in the south I have more signal and less need antenna fellow north, so I indicated that I cheat and I'm not a good reference.
And could live where you indicate. I live in a village north of Madrid more capital in a village community in Madrid indicates my signature (40.545847, -3.612012), less than 3 KM that point (IKEA).
img_a4540.gif


I'm outside the official satellite footprint.
Then I send data 100% in San Google, as always, the antennas look good.
It is an OS-100 STB antenna, the actual measurements are 98x90cm, they would have to actually sell as 90cm by physical measurement are 0'692m², which corresponds to an antenna of 94cm (quick calculation, the average of its measures 98x90 = 94xm ).
The 2000 my friend recommended that I participate in its design, its performance compared to other antennas of larger measures.
------------
Al vivir por el sur tengo mas señal y necesito menos antena que los compañeros al norte, por eso indico que hago trampas y no soy una buena referencia.

Ya podia vivir donde indicas. Vivo en un pueblo mas norte de Madrid capital, en un pueblo de la comunidad de Madrid segun indica mi firma (40.545847, -3.612012), a menos de 3 KM ese punto (IKEA).
img_a4540.gif


Estoy fuera de la huella oficial del satelite.
Luego te mando los datos 100%, en San Google como siempre, se ven las antenas bien.
Es una antena OS-100 STB, las medidas reales son 98x90cm, se tendria que vender como de 90cm realmente, por medidafisica son 0'692m², que corresponde a una antena de 94cm (calculo rapido, la media de sus medidas 98x90=94xm).
El el 2000 me la recomendo un amigo que participo en su diseño, su rendimiento la compara con otras antenas de medidas mas grandes.

The gain is/La ganacia es de:
10'7-11'70Ghz.- 40'2dB
11'7-12'50Ghz.- 41'0dB
12'5-12'75Ghz.- 42'0dB
3.jpg


Going up, wipe a little antenna, I have one family of owls in the area and liked the antenna to finish eating prey that hunt, do not see the gifts left by the "bugs" on the antenna and the wall that is behind .
-------------
Al subir, limpie un poco la antena, tengo una famila de buhos por la zona y le gusta la antena para terminar de comer las presas que cazan, no veas que regalos dejan los "bichos" sobre la antena y el muro que se ve detras.
 

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Last edited:

RimaNTSS

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@Tururu
It is an OS-100 STB antenna, the actual measurements are 98x90cm, they would have to actually sell as 90cm by physical measurement are 0'692m², which corresponds to an antenna of 94cm (quick calculation, the average of its measures 98x90 = 94xm ).
Antenna you have is 90cm. Small axis size represents the size of the dish.
 

Tururu

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@Tururu
Antenna you have is 90cm. Small axis size represents the size of the dish.
True, it is 90cm, but the gain has sold as 100cm.
For a topic with fellow Huevos and measure its useful surface is 94cm (0'692m²).:-rofl2
----------------------------------------
Cierto, es de 90cm, pero por la ganancia que tiene la venden como 100cm.
Por un tema con el compañero Huevos y medida sus superficie util, es de 94cm (0'692m²).
img_a4540.gif
 

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True, it is 90cm, but the gain has sold as 100cm.
For a topic with fellow Huevos and measure its useful surface is 94cm (0'692m²).:-rofl2
@Tururu Sorry to disappoint you, but many sellers show bigger dish size just to be able to sell it better.
And secondly (disappointment again) your dish is visible from satellite with it's surface is 0'636m² :eek:
Want to argue or ready to accept this as it is? :D
 

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Back to topic: So I have finished measurements and do not think I can do any better for this CM 1,2m dish.
Used laser to see where LNB is pointed and digital protractor to measure angles IMG_20150531_183858 (Large).jpg . Leaning of line from F towards dish was 66,3*, line A-B was 1,8*, that means angle between those 2 lines is 64,5*. Remeasured more carefully lines A-F and B-F got 1224 and 714mm. Therefore original LNB holder holds LNB in such a way that it's Phase Center is only 7mm from Focal point of the dish (pink line =7mm) ScreenHunter_347 May. 31 20.54.jpg . What spoils everything is direction of the LNB, so line from LNB hits the surface of the dish 126mm higher than it should be doing that. One could think, OK, we should lean LNB little bit lower and than it will be pointed to the right direction and issue will be solved! Bright idea, but will not work like that. If we lean LNB more down than it's Phase Center will also go more down, so situation will be even worse. To solve the issue, I suggest to make another LNB holder and then you will improve system performance at about 5%, which is more or less equivalent of increasing dish size for about 10-15cm.
On the drawing everything colored blue is calculated, everything in green- carefully measured ParabolaCM120cm (Large).jpg . That is all for today folks. ;)
 

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I would like to see the same tests with the dish set up on a PM tracking the arc with no alterations from the initial setup at 0.8w/ whatever it is for your location. I am sure your positioning of the LNB wont track the arc properly from my test.
 

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Martin! If it is possible to get improvement of reception on one satellite than it is possible to do the same on any receivable satellite and also across the whole arc. My arc on the balcony is small, therefore I did not adjusted whole arc after changing LNB holders. My central satellite is 4,8*E and 7,3*W is relatively not so far away to mess with declination and elevation adjustments, enough to do only elevation, azimuth and LNB skewing.
Anyway, original CM LNB holder sucks :D
 

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Martin! If it is possible to get improvement of reception on one satellite than it is possible to do the same on any receivable satellite and also across the whole arc

Nope, try it :) I have, it loses the arc ;).
 

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Than adjust your arc and you get best signal on all satellites.

Please do the test and tell me the same, i am always looking to improve my setup, and modding the LNB holder will give more signal but it loses the arc, anyone with a fixed dish go for it, it will give you more signal, but if your dish is on a PM leave it as it is ;).
 

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Sorry Martin but I disagree here :D Changing of position of LNB can not make impossible to tune antenna to the arc. It is just matter of adjusting of the PM.
But, of course, I will do some tests anyway. Will adjust dish to the maximum possible arc with original CM LNB holder and do measurements on most-West, central and most-East satellites. Then will change LNB holder, adjust PM and do tests on the same 3 satellites. Of course I will do that someday. I have no doubts on positive results.
 
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