How important is Dish alignment? Watch out - Signal boost! ;)

[Phoenixx]

Hi all Satters, Update .. Amazing Dish Emprovemant ;)

This Sunday afternoon i try to get my feedhorn exactly in the hard of my Jonsa 180 pf dish.
I have an idea to get a tiolet koker thats fit exactly to my feedhorn rings to get an
good indication of angle when i stand at the opposite from the dish and align the feed
now woth this help in to the middel of the pf dish.

Its also possible with my yellow waterpass angle meter.
Dish angle must be the same as feedhorn angle.

The first result was a lower signal but that means two thinks:

- The feedhorn was not exactly into the mid of the dish
- Reangle the dish to the zenith 0 grad south for me its siries 5 E
- Clarcbelt check Badr 26 E to get also ther optimal signal
- Turn dish little down to get the weak of Badr transponders
- Back to zero optimize with Sirius
- Badr check for the weakest transponders
- If ale good go to 70.5 E and check the signal
- If its all good then the dish is sygronizised to the clarcbelt.
- With 1 polarmount from 50 W to 80 E ;)
- Make sure that the feedhorn distance is good and exactly in the center.

After succesful aligment, all satelites arrived good and beeming good into the dish ;))

Note that not the full size of the dish can be used becaus some angles are blocked
from my balcony. For 70 E the sat bundle arrived few meters from the church roof
to the 70 E satelite.

Some people say in some forum that the Jonsa 180 pf dish was garbage and can not used for ku
but if you handle the rules also with wire around forside from the dish angle together in the middel and the wire do not touche each other then the dish bundle is optimal and low ber and
an easy lock with weak signals.

I am impressed with the results of my cheap primefocus dish, 70.5 E 11210 V is booming in ;)
And .. take or modify an lnb with a good cros polarisation > 25 db the result is amazing!.
later i wanna try an Smw lnb, expencive but good for feedhunting.

Happy Sat dxing from Holland.. ;)

 

[RimaNTSS]

Could you show pictures of your antenna? For the interest: Can you turn antenna to Eutelsat 7 West A @7,3*W and announce signal level?
There is mine, received on 1,2m dish not far from you.

 

[Phoenixx]

Yes offcause, this is my dish on my balcony and recive good signals.
Nilesat arrives good here in Holland but the dish are blockt from the upsite from the roof
from the neigbours and the pertinax plate 80 cm from the ground.
Even that i have enough signal to recieve Nilesat.

later i will get another dish with a f/d of 0.42 because the randement is higher then a dish
with an f/d 0.38 because the angles from the feedhorn are always have the lowest signal transmission.

Then i want to try to make a Cassegrain from the Jonsa and replace the lnb for a reflector and 30 cm inside the lnb with fixed feedhorn to get optimal signal. Then i don`t have also the feedhorn optimum flat for all frequentions because adf 120 and other feedhorns are not good gaining at the lowest astra 2 f freq 10.900-11.000 Ghz.

Ofcause i recieve Astra 2 but i want a flat frequentie gain in my recieve signal, i have also buy 2 inv black ultra to modify, 1 lnb for my prime focus dish and 1 for my offset dish ;)

 

[Channel Hopper]

This Sunday afternoon i try to get my feedhorn exactly in the hard of my Jonsa 180 pf dish.
I have an idea to get a tiolet koker thats fit exactly

Is this red light district talk ?

 

[RimaNTSS]

Nilesat arrives good here in Holland but the dish are blockt from the upsite from the roof
from the neigbours and the pertinax plate 80 cm from the ground.
Even that i have enough signal to recieve Nilesat.

Somehow I doubt you easily receive Nilesat in the Netherlands. Maybe you receive Eutelsat 7 West A, which is receivable in our area. From Eutelsat 7 West A I was asking about one particular transponder, which is
11661V 2/3 27500. So, if you can get it, could you say what the signal level is?

Then i want to try to make a Cassegrain from the Jonsa

This is interesting. Before you made it, could you tell the idea? I mean, how are you going to make subreflector?

 

[archive10]

Some people say in some forum that the Jonsa 180 pf dish was garbage and can not used for ku.

Good to hear about the positive results.
My main gripe with the Jonsa 1.8PF for Ku is that it's obviously designed for low-cost C-band deployments in dry climates.
Accordingly:
1) You need special feed-horns (jonsa don't make 'em) and C120 LNBs as the dish is 0.36 f/D, most integrated Ku LNBs are 0.6.
2) The dish is not galvanised and the coating comes off whereever there is conteact with other parts or screws.
3) Comared to a plastic dish of same size, it is extremely difficult to get the same performance no matter how much tweaking and updating is applied.

My dish was a difficult to assemble (required stringing and careful alignment of the petals), and the result never got better than a Black Ultra on a 120cm SMC dish.
I am not saying it can't be done - you have obviously had more success with it. I jut didn't in the end.

Mine started rusting the day I installed it. And then later that year, an autumn storm took the reflector off the circular based and put it at the end of my garden.
Lucky it didn't hit anyone...

It probably fares a lot better on a balcony

Good luck with the project!

 

[Phoenixx]

The rust from the Jonsa is a problem i agree @ st1 thats why i first want a few thinks for
testing and later replace the dish for a better one. The f/d from Jonsa is 0.38.

Two years ago i have install the pf dish o my balcony and set the reflector in 3 parts
of two reflectors at the same time, so first 2 inside home connect and bring it on dish
and then 3 times because dish on te ground to aligtmant the panels have no space for it.

You can aligtment the dish with horizontal and vertical wires so they just don`t
touch eachother an play with the panels to get tuned the maximum of it with 4 wires.

The i replace the invacom lnb and make a mod lnb from the ap 82xt2n ku lnb and cut off
as short as possible and later replace the adf 120 for my old triax pf feedhorn from
the old analoge times for testing. The signals are good badr 11919 are 85 % to the
Clarctech 5100 Combo reciever. I have 24 " to drive the arc at 47 W to 72 E

First tuning from 0 south (Sirius 4.8 E Amsterdam / Beverwijk) was good and signal
on my Clarctech was 90 % , then i go to Amos 4 w and have good signal and retune
and note steps from my vbox. I don`t need memory from my reciever to drive i tune
directly to the sat ;)

later i test nile sat an quatar was the first station to cache and gives 53 % on the
Clarctech, with retune steps and angels i have be clean weather 57 % that is terrific!

Note for Nilesat my balcony blocks the upper and a part of the lower site of the dish
so the realy virtual dish is i guese 1.35 insteat of 180 so when i compare at the full
diameter to recive the nilesat 201 booming in and also nile 102 the old one can be recieved.

The subreflector i want to test have the same diamater as the conical rings from the c band
i how have on the dish, and the same angle and f/d as the dish, i must be found someting
as a part of an old footbal with aluminium folie. The other site to the lnb must be
a sort of fibo horn with variable distence to tune for optimal signal.

The 11.919 from Nilesat are earlier 50 % on my technomate 5500 HD with sharp tuner.
Have a good axample at 70,5 E for picture..

Later comes from ku a Deltaster fibo 120 and then i can chack 11919 from Nile again.

Ger..

 

[RimaNTSS]

The subreflector i want to test have the same diamater as the conical rings from the c band
i how have on the dish, and the same angle and f/d as the dish, i must be found someting
as a part of an old footbal with aluminium folie. The other site to the lnb must be
a sort of fibo horn with variable distence to tune for optimal signal.

If you have this subreflector at your hands, could you show some pictures of it? And what shape this subreflector has?

 

[Phoenixx]

ok good ;)

 

[Phoenixx]

Update from the cassagrain project:

The cassagrain has a better cros polarisation and a lower beamwith so the quality of weak signals wil be better
Also the critical f/d and the problem with adf 120 scalaring s optimalisation only for 11 --12 freq problem is solved
becaus you can use the rave feedhorn as horn to mach a c120 lnb or manuel omt with twe norsat 8515 for exelent recieve quality
I think it`s a good idea to convert prime focus dish to a cassagrain antenne.
First i have thinking and search and i found someting intrested an worth to try working ;)

 

[Trust]

Nice find that drawing , stored for when i run out of projects .

 

[Phoenixx]

Update ..

Ok Trust thanks for the replay and good to get on the cassegrain, its worth to work.. ;)

Today i must working on the kringloop factory and i have found a second big subreflector
in the metal part and i found also in the playground colored wires to check the accuraty
of my prime focus dish because i have before a few time ago the panals a little turn
backwards to expiriment with the f/d but i want to set the panels as accuration as
possible to create the maximum gain from it..

What i can do is let the c band holder into the Prime focus dish and draw a 6 mm into
the reflector and put it on the foresite of c band scalar rings.
I know the distance is importent but if the distence is shorter or longer then you
can tune the distance from the reflector to the horn to get maximal signal so there is a
marge to combinate both distances and get the best part of signal, first with a strong
transponder and if all angle`s are correct then the weak transponder and when all optimum
is present then go to Nilesat and we shal see what happend ;))

It`s also a interest thing to ecpiriment with the horn. There are diffrent horns to recieve
like the channal master or gibertini or raven feed (tuned low band astra 2g) or fibo feed.

If you have a rillen feed those feed are always have a optimum in the frequention band
but it is also possible to get 2 omt stube copple to improve the cros polarisation and
if the omt`s ar build to get 2 for ku and 2 for c band resp h/v and circulair l or r
and ku bss cirulair all in one phase wit optimum performance, where do you find that ;)

If you want a maximal cross polarisation use the side of the omt and not the lengt
to the output, use this as the vertical because most the horizontal transponders
are weaker and need a little more cross polarisation..
View attachment 80148 View attachment 80149 View attachment 80148 View attachment 80148 View attachment 80149

 

[RimaNTSS]

@Phoenixx I hope to not disappoint you but using coocer's lid will not bring you any positive results. Also your another find, namely "big subreflector" does not look like subreflector of the Cassegrain antenna.

 

[archive10]

Now, I do like experimental approaches to antenna building - sometimes it can be quite an eye-opener.
And I do support the experimenters; these guys are where we get inspiration from.
So do please try your ideas out, and let the forum know what your findins are.

But there a few points that are not clear to me in your writings, or could benefit from some discussion:

1) Are you trying to build a Gregorian or Cassegrain antenna?
Gregorian antennas have a concave secondary reflector, Cassegrain ones have a convex.
Cassegrain often have a focus in the center of the primary reflector, allowing reception electronics to be behind the bigger reflector, out of way of the signal.
Gregorians, such as the Fibo design, often put the focus point between the refletors, closest to the secondary.

2) Sub-reflector construction.
The secondary reflector (aka sub-reflector) is generally made a a sperical (or elliptical) shape.
Kitchenware lids are normally not designed to have specific spherical properties.
The green one you have is unlikely to be designed as a spherical shape...

That is not say that it won't work - it's just not a given that it will perform better then not using a secondary reflector.

Your idea with the football and alu foil is probably going to yield better results.
Although I would probably be using something like a (new) bowling ball, and put a couple of successive coats of reflective paint on it, then continue with resin and fibreglass fibres until you have a couple of mm of thickness. Then remove from ball and trim to size.
The only problem here might be the required size of the bowling ball - see next issue.

3) Feedhorns and f/D translation.
As you indicate, feed-horns need to be tuned to the f/D of the dish as seen through the secondary optics.
For Ku-band LNBs, it would be possible to use high-performing Ku feed-horns and C120 LNBs (or even modded universal ones), as you would be able to translate the f/D of the PF dish to the f/D of the feedhorn.
But you need to make sure that your secondary reflector accurately translates the around 0.36/0.38 to the around 0.6 f/D of the most common Raven/Channel Master feedhorns (and similar). This calls for the correct size and opening angle of the secondary reflector.
Considering the f/D of the PF dish, you will need probably need a *very* large bowling ball, or make your reflector fairly small (and thus difficult to tune and more susceptible to geometry errors and reflecting surface defects.

So get out the slide-rule, and start calculating the size of that bowling ball...

 

[Phoenixx]

Update..

One step further

First question whay not experiment and try to get the best out of the antenna specealy
when i have the idea for a little time against to 7 years of search to find the inv
black ultra lnb ? If there was no passion to find out, the lnb was probly not found ..
So i agree @ sd and thanks i am a little step further..

The second idea was to search the internet and i found a radar page where are the same
info was printed with a cassegrain reflector with radar basics ..

http://tiny.cc/1bawzx

If you are look carefully you can see that the curve from the dish is the same curve
of the reflector..

I has another idea to go to satlex and find the f/d from the 3 reflectors..
the curve from the forside is the same (mirror) curve on the backside ..

- First the grean reflector 27 x 175 mm > satlex > f/d 0.41 lnb distance foresite > 7.09 cm
- The second big reflector 77 x 265 mm > satlex > f/d 0.22 lnb distance foresite > 5.70 cm
- The second kook reflector 15 x 150 mm > satlex > f/d 0.63 lnb distance foresite > 9.38 cm

- Note thats the dicetance when you use a reflector to the forsite against the dish..
- This is the opposite site from the reflector so the backsite has a longer focal distance.

- The f/d from my dish is 0.385 .. ( must reangling the panels to exactly 0.38 )

- Note, the fibo is the same idea anly for the offset antenna..
- Also the fibo can be optimezed with a second reflector to improve
the cross polarisation agains one reflector..

Read ..

http://tiny.cc/ibawzx

- I found it worth to expiriment and optimize the angels to get the best out of the dish..

We go on .. ;)

 

[RimaNTSS]

If you are look carefully you can see that the curve from the dish is the same curve
of the reflector.

If you look carefully you can see that curve of main reflector of all dishes (PFA and Offset) is always -PARABOLA
Subreflector of Cassagrain antenna is always - HYPERBOLA, subreflector of Gregorian antenna is always ELLIPSE. And there are big difference between those 3 geometrical shapes. You can not use 2 paraboloids to make Cassagrain or Gregorian antenna.

- Note, the fibo is the same idea anly for the offset antenna..

Fobo is not the same idea, as it is Gregorian antenna.

Of course, it is always good to experiment, but direction of experiments should be right, or that will lead you to nowhere.

 

[Phoenixx]

ok Rima youre right i have study some thinks and search for awnsers and indeed
the reflector must be am hyperbole and not an parabole.

Further i have seen a lot of calculation how to find out the optimal form and
the other methode is to sign a elipse from two points to get the optimal form on paper.
If the reflector is good i try to find the reflectig angle of 60 gread for a normal
black ultra lnb to see what happend with the signal.

When i test and get the dish to a strong satelite for example hispelsat then i have
always signal on my trimex 3500 realtime spectro meter, the point is to get the signal
bundle backwards to the begin of the dish. How longer the reflect bundle how better
the cross polarisation and how lower the ber and cleaner the signal i think..

I have read a lot of intresting things on the russians forum to make a good cassegrain
reflector..

But first i have aligtment my Jonsa Dish and increase the two cm spatial between panels
to almost zero in the dish, the panels are now almost optimal in acurate prime focus form ;)

 

[Phoenixx]

Info to make a good cassegrain reflector, i wanne try to get it working with the inverto black ultra lnb with feedhorn.

http://www.w1ghz.org/antbook/conf/Multiple_reflector_antennas.pdf