Tests of 120cm antennas

[RimaNTSS]

OK, as I got more or less enough 120cm antennas I am going to perform some tests of them this year. Only plastic dishes will participate in this competition, I also have couple of 120cm metal dishes, but, most likely will not add them to this test.
#1 - CM120;
#2- NSC 120 (Made in West Germany, means quiet old one);
#3 - Cēsu 120 (Latvian product);
#4- Visiosat 120 (hope to have it this week);
And maybe also #5 Echostar 120 (if I manage to find one at all).
So, my testing steps will be:
1 - String test them to make sure they are not warped (warped ones will be excluded from tests);
2- perform exact measurements of dishes, if possible, calculate their offset angles, opening angles, Focal points, "Le point G";
3- check whether original feedarms hold LNB in proper place and LNB is pointed to the right spot on the surface of the dish. Laser-pointer will be used to check aiming of LNB.
4- will install IBU in original LNB holder on original feedarms and point antennas (one by one) to satellite which has variety of transponders across whole frequency range, and where are weak and strong signals. And is better this satellite is on the top of the arc. I think that will be 28,2*E
5- Will scan all frequencies and record signal levels to use this data for future comparison.
6- If original feedarms are not holding LNB in the right place than will probably make new feedarms and do scanning again.
7- if have enough time than install different subreflectors to dishes and record data again;
7- after all test are done and all data in the spreadsheet, will draw some conclusions and say which system perform better and also how much better it performed.
That is the plan. As we know, not all the plans are executable and they can be changed immediately after start, but, anyway it is better to have bad plan than do not have any
O, yea, critics and ideas are very welcome!

Test "rabbits"

 

[archive10]

Suggestions:

1) I doubt stringing will be necessary - only to detect very bad mould technology.
Point is that warping of dishes is a metal-dish phenomena. You just don't see it in the plastic dishes.
(Also, you need to assume that the front rim of the dish face is in fact intended to lie in a plane. In principle it could have any shape, as long as there is a parabolic reflector.)

2) Check reflectors for steel-mesh reflecting effeciency - use radar devices (e.g. automatic door opener or similar) to check how much signal the dish absorbs / reflects in a small area.
This is not uncomplicated - but would ideally show reflectivity, absorption and pass-through at frequencies from C-band to Ka-band.

3) Ideally, you would also check performance of dish-feedhorn combinations of the dishes.
different feed-horns may match difference reflector effeciencies better... Can't quite get my head around how that would be practically done, but I'm sure someone can come up with a suggestion.

 

[Captain Jack]

Will be very interesting to see the results of this.

Any chance of a Laminas 120cm test?

 

[gibertini]

thought i was nuts having two 1.2m cm, one 1m cm and one 1.2m echostar smc dishes here but you put me to shame @rima.. triax do a 1.2m smc dish also but looks like a badged skyware

 

[RimaNTSS]

1) I doubt stringing will be necessary.................
.......... In principle it could have any shape, as long as there is a parabolic reflector............
2) Check reflectors for steel-mesh reflecting effeciency...............
3) Ideally, you would also check performance of dish-feedhorn combinations of the dishes......................

1- Agree with that, but stringing is not so difficult to do. And I have some doubts about perfectness of SMC dishes, especially when you attach weight to lower part of it, such as LNB or several LNBs. Usually dishes have flat surface with some exceptions, like my #3. Those, not standard dishes are not very grateful to work with- impossible to calculate all needed angles and Focal point.
2-Sounds too complicated, and I am not ready to do this....
3- Could probably also try to uses several LNBs and feedhorns, but something tells me that IBU will bring best results.

Any chance of a Laminas 120cm test?

Yes..... if you provide me one Same applies to 1,2m Gibertini SMC

but you put me to shame

Do not worry, you still crazy enough

 

[Captain Jack]

Gibertini didn't do smc dishes... Their 1.2m is aluminium construction.

 

[timo_w2s]

Looking forward to seeing some of the tests.

I'm sure you've already thought of this, but worth keeping in mind signal level variation where you are close to the edge of a footprint. This may not be an issue for you at your location but levels can change fast even if weather remains stable for some satellites.

 

[Riverblue]

Test "rabbits"

"Guinea Pigs" ;)
Looking forward to your results.
Nice find that 120cm Channel Master with a polar mount! It looks almost new.

 

[samoloko]

test will be no serious If you do not compare to Gilbertini

 

[RimaNTSS]

test will be no serious If you do not compare to Gilbertini

Why?

 

[RimaNTSS]

I'm sure you've already thought of this, but worth keeping in mind signal level variation where you are close to the edge of a footprint. This may not be an issue for you at your location but levels can change fast even if weather remains stable for some satellites.

Yes, I did think about doing tests in same weather and time of the day conditions. Installation and tests are going to happen in Latvia, where we do not have 28,2*E signals very strong, and some beams, such as UK one, are even not receivable on reasonable dish size (under 3 meters)

 

[Huevos]

Laser-pointer will be used to check aiming of LNB.

Be careful not to burn a hole.

 

[PaulR]

LOL, I think we're talking microwatts not James Bond splitting power here.

 

[samoloko]

Why?

gibi Is regarded as one with the highest gain

 

[RimaNTSS]

gibi Is regarded as one with the highest gain

Do they make 1,2m plastic dishes? I can not find any

 

[samoloko]

thread title does not say anything about plastic

 

[RimaNTSS]

thread title does not say anything about plastic

But if you read first line of my writing than:

Only plastic dishes will participate in this competition

Even if metal dishes would be allowed, do Gibertini make 1,2m dishes? Or their dishes are little bit bigger? If they are bigger than test would be not fair, something like comparing uncompilable things. Why not add to the test CM 1.8m dish then? That would probably perform even better with better gain?

 

[Captain Jack]

I think adding a Gibertini is a good idea. They are not plastic but aluminium. The width is 125cm so slightly larger but not by much. Also, it's the dish that a lot of people ask about when comparing it to a Channel Master. It's not like comparing two completely different dish sizes as it's so similar to others. The tests and results might help people make a more informed decision when picking between the two dishes...

 

[Riverblue]

But CJ if you add the Gibby to the test then you should get better results with it as it is bigger! On a like for like basis with the type of lnb, weather conditions, positioning etc being the same for each dish then size will surely be the difference. I thought Rima's point was to see which was the best performing "plastic" (SMC, fibreglass etc) dish of the same size, 120cm. I get your point about the Gibby as a comparison, but if you start adding different sized dishes then where do you stop, 1.5m, 1.8m?

I think Rima's reasoning for this test is because there are so many of us that speak so highly of our Channel Master 120cm dishes that now he has got one he wants to see if they really do perform as well as we think they do, or are they just the same as a similarly made same sized dish!

 

[RimaNTSS]

Agree with Riverblue, if Gibertini dish 125cm than it, only because of bigger size should work better than CM1,2m by some 8%. But, from another hand if we compare 2 dishes 1,2m and using proper LNBs at the same weather conditions we will, most likely have exactly the same performance of systems. Or difference will be under possibility to do precise measurements.
Another issue- I do not have Gibi 1,25, do not want to spend money on it, and, TBH, do not want to spend any money for any dishes anymore. It is time to stop someday.
I have aluminum 1,2m PFA Kathrein, can also try to add it to test.