Anyone tried to make BIG dish at home?

[JanH]

I have made LNB cooling test.
I use older Sharp LNB without plastic cover. Satelite 19,2 ASTRA, offset dish, multifocus, signal adjusted exactly above erros. LNB temperature before test 22 degree C. Receiver Dreambox DM 800 HD show S/N 10,6 dB. I use cooling spray with declared temeperature -55 C. I do not know exact temperature because my easy IR termometer do not measure it.
LNB was frostliness for some minute then recever show S/N 11,0 dB. Level was stabile for some time.
Nothing dramatic, small change.

Looks for nothink.
JH

 

[Captain Jack]

Would be interesting to see this on weaker satellites

 

[JanH]

Atmospheric conditions make much biger changes. I change dish setup for test to make signal smaller.
I mean, may be visible but not too practicle for 0,4 dB S/N.

 

[TheToad]

Is there a website with information on how he did this?

 

[JanH]

Any idea how to make big dish?

Dishes array exist. Have anybody idea how it is designed?
It is not possible to simply connect more ordinary LNBs together.
_http://en.wikipedia.org/wiki/Very_Large_Array
JH

Moderation Note

Please remember - no live links to outside sites

 

[mouse3]

Any idea how to make big dish?

Dishes array exist. Have anybody idea how it is designed

This it s one million dollar question .
Well,connecting more parabolic dishes to decrease the reception noise after my opinion have sense only to connect all dishes array focal point in one single spot.
But,looks to be samthing new,maybee it s the future.That dish farm relocate the dish position on field for maximum gain and directivity on rail.
Maybee the farm secrets are classified for us.Deserve more investigations this subject.

 

[JanH]

They may use arrayes to see biger part of space, huge dishes should have extremely narrow beam. Means each dish is pointed to other close point.

What about your BBC project. Some progress?

 

[mouse3]

They may use arrayes to see biger part of space, huge dishes should have extremely narrow beam. Means each dish is pointed to other close point.

What about your BBC project. Some progress?

The size of each dish it s not large enough for deep space.If it s true the project it s born dead.Maybee the space it s only coverage for samthing else.
Well,about BBC nothing yet,i must relocate away from town fxxxxx legislation against larges dishes first,after lots of possibilities are ready for test in the back yard.
Cooling equipment must be ready soon for testing.Unfortunately my job it s 200 Km away now,this delay my project.Delay only,not cancelling.
This toy keep me bussy for now.

 

[JanH]

Tell us more about your toy with adjustable wrench please :-)

 

[mouse3]

This dish it s made in China and it s very cheap here.The subreflector it s 20 years old and one guy give me for free.It s from commy times,manufactured for exports,it s old and rusty but perform well.I spend lots of time and beer to adjust the focal point and found the maximum gain from this 0,9m dish.Becose the dish it s small have nothing to do with DX-ing ,but the experience it s good for future projects.
I want to test pipes to connect more dishes focal point in one for DX-ing.This test it s very important,SHF are hard to handle.I want to remove the subreflector and install one mirror 200mm x 200mm and see what s happens with the signal.
Next,i want to install lenses before pipes from optical kit in the focal point,maybee helps,i dont know yet what happens.Last experiment with pipes failed on Ku band.Samthing go wrong,after one 90 degree curves and 200mm pipes Ku signal it s lost. Why ? I need for each dish two 90 degrees curves and 3m of aluminium pipes.It s enough for one Ku band array made from 4 dishes 3m diameter.

What have this device and SHF works and why failed on my experiment.Comments are welcome.

 

[JanH]

Giant and very interesting project. I can not imagine four 3m dishes on my garden if space enought. It is really fantasy.

I think it is about impedances.
I suggest use feedhorn cated from LNB to convert dish impedance to pipe impedance and use same diameter pipe as LNB have inside. Other side could be append to LNB without feedhorn.
Four pipes connected together means 4x smaller impedance, which should be converted back. Maybe help some lamda/x pipe (strongly depend on frequency) or some cone piece connected identically to LNB without feedhorn. Pipes must have exactly same length perferably lambda or lambda/2 to have same impedance on input and output.
There were old fashion feedhorns designed with flange to pipe as well as LNBs.

I have no idea if or how subreflector can change impedances. Probably yes.
JH

 

[T1154]

Wow!!
I could get a 4x3m array in my Garden but I think it would result in a visit from the Maire. All French citizens have right to install a Dish on the property they occupy but that would be stretching it . [ I already have 5 and I'm not a citizen, but I think perhaps that after twenty years I am tolerated ]
The system you are proposing. Would it have a feedhorn on each dish , with an identical length of wave guide from each to a combiner assy., whose output pipe would couple to the flange on the LNB ?
It seems as if 'mouse' must have encountered matching problems on his rig?

Alas its a long time since I played with pipes! T1154

 

[JanH]

Another point of wiev:

Dish gain should be eqal of dish ortogonal projection of dish area in satelite direction.
One 3 m dish have area about 4.7 m2. Classic round parabolic dish.
Three 3 m dishes are 14 m2 which eqal area of 4 m dish.
Am I crazy or not??

Maybe it is more easy to make 0.5 m collar round the 3 m dish?
There must be losses on pipes etc. and I can not imagine how to point 3 dishes to same very low signal satelite.
JH

 

[mouse3]

Maybe it is more easy to make 0.5 m collar round the 3 m dish?
There must be losses on pipes etc. and I can not imagine how to point 3 dishes to same very low signal satelite.
JH

Homemade extension for Ku band perform bad,the shape accuracy it s beyound us.
I make the pipes test,sory about the picture quality,next week-end on daylight i make more.
Signal turns 180 degree on pipes and the signal strenght decrease by 20%.
Between curves i want to install 3m pipes to see what happens,if it s works Ku band array project become possible for DX-ing.
How to point 4 dishes to satellite ? One dish at the times,after few hours are all dishes installed,one next to other,pointed to the same satelite.Astra 1N for example

 

[mouse3]

Here are the picture about,it was very intresting day,today.
Here it s winter time and it s cold autside,below 0 Celsius,maybee sound crazy,but i want to make one small hole in the wall ant to have the copper pipes inside the room for advance testing.
6 months of boring winter become 6 months of testing Ku band frecvency inside the house...

 

[digihoe]

Wow, looks like a big project! How is the LNB skew affected, do you see big diffrence? About pointing multiple dishes, how will will you know what the optimal positioning is, have you seen any signal pattern studies?

Good luck and best regards!

 

[mouse3]

Studies,no,and what pdf i found are floded with high level of matematics,hard to understand,testing at home after work...it s the best teacher,learning from mistake.
Skew it s not affected,i m free to turn LNC to falow the signal anywhere i want.
Optimal positioning for dishes it s not one big problem,one dish near other the pipes must be short as possible.The ammount of signal lost in the pipes it s all i want to know for now.

 

[JanH]

I see pipe variants on pictures. What is main problem for lostes? Distance or curve?

It may possible to use soft copper pipe instead semi-hard material. It is usually used for clima installations and it is easy to bow. Idea is to use one piece pipe and reduce lostes. Maybay

 

[mouse3]

Well,first i must buy 4m hard copper pipe and test on real conditions,but after New Year.
After each curves signal turns,skew to be more accurate,so,all curves must be the same and exact number otherwise skew it s not the same for all dishes array.
I hope You understand now,it s talking about skew only.I found no loses on signal where curves and pipes are connected with screw and O-ring.
I don t know what it s the main problem yet,distance or curves.

 

[JanH]

Yes, it is result. I did not think about skew yet. It should be about pipes angels only.

How to a bit change skew to adjust system? Ferrite-magnetic polarizer, what I can remeber.