Anyone tried to make BIG dish at home?

[Low Profile]

Without looking it up, I seem to remember from college days that noise is proportional to the square root of temperature (measured in Kelvin).
(In a receiver noise is proportional to √4KBTR)

 

[JanH]

Without looking it up, I seem to remember from college days that noise is proportional to the square root of temperature (measured in Kelvin).
(In a receiver noise is proportional to √4KBTR)

What do you think about LNB cooling?

 

[Low Profile]

It's not something I do myself and would be a little reserved about thermal shock, that said, I appreciate the benefits for fringe areas where signal to noise is critical.
One other thing you might want to consider is your coax run. If you bury your coax you will see noise reduce - particularly when the sun is high (but pay attention to water ingress).

 

[JanH]

Bury coax. You mean to cover cable between LNB and receiver?

Air RF signals on cables surface can make problems. I use ferrite rings fasten outwards cable. It sometimes helps improve signal.

For me usage of freeze LNB is a bit far away from my ordinary live. But I like to try it. Main problem is rain and tiling roof now

One more think is antenna painting. Long time ago ( ECS 1) I checked different paints for dish. For example some green paint cancel signal at all. Mayby if signal is very low, we can take care about dish temperature or it colour too.

 

[mouse3]

Bury coax. You mean to cover cable between LNB and receiver?

Air RF signals on cables surface can make problems. I use ferrite rings fasten outwards cable. It sometimes helps improve signal.

For me usage of freeze LNB is a bit far away from my ordinary live. But I like to try it. Main problem is rain and tiling roof now

One more think is antenna painting. Long time ago ( ECS 1) I checked different paints for dish. For example some green paint cancel signal at all. Mayby if signal is very low, we can take care about dish temperature or it colour too.

Why You not ask before about painting ?
Vadova and Adhezor it s metal free paint.Have no metal inside that composition,so, perform excellent like dish painting.Here i have few guys who buy from Hungary this paint.
Post please,one photo with ferrite rings.it s the same like the ferrite from computer data cable ?

 

[mouse3]

I If you bury your coax you will see noise reduce - ).

You means to burry cable underground ? If the cable it s inside metal pipes,old fashion pipes,not plastic the effect must be the same.Intresting subject for fringe testing,thanks.

 

[Low Profile]

The idea is to keep the cable cool, if a cable is left in the sun it will get warm and noise will increase.

 

[mouse3]

The idea is to keep the cable cool, if a cable is left in the sun it will get warm and noise will increase.

Thanks,i have one more question to ask.If i remove the receiver tuner from the box with all the RF measures for interefences done,it s possible to increase the tuner sensitivity cooling to -50C like LNC ?
Tuner it s mounted in the protective box,replace air with nitrogene for example,no air,no moisture,no condensation inside that box.
One option it s to be mounted near to the LNC in the same insulated box in the focal point of the dish,100mm coax cable only.From there few wires to feed the box,maybee coax if it s necesary,in this case signal lost it s reduce to a minimum rate.
What do You think,for fringe each fraction of dB counts.

 

[JanH]

LNB gain or LNB signal output level should be sufficient to make receiver input noise minor. Long cable from LNB to receiver could make problem. Usually about 100 m long cable is as limit. Of course it depend on LNB, cable quality, recever etc. If problem then can help through amplifier doas not metter noise parameter in the somewhere midle of cabling or midle of signal attenuation. Most important is receiver bandwith for S/N result. It is a bit complicated problem and I do know how exactly modern receivers designed.
I think it is same for cable bury. Only problem with cabing is attenuation and RF parasit interference going by cable surface which may influence, congest recever input. All other should cover LNB gain if enough.


I have made LNB cooling test.
I use older Sharp LNB without plastic cover. Satelite 19,2 ASTRA, offset dish, mutifocus, 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.

 

[mouse3]

This autumn my cooling LNC refrigeration units must be ready for testing at -50C.When it s i make the test for 2 D.Years ago i make one cooling LNC units from one butchered home freezer at -35C.On analogic signal increase by 50%.On today digital signals i have no ideea what happens.

You adjust signal above errors,if i understand well,in this case signal it s okay before testing,adjust signal below errors,only pixelation available on the screen.In this case cooling the LNC and image must „flow” perfectly for a few seconds.


Here are available only crap amplifiers,quality it s not there, add more trouble this amplifiers then save the day.I found only trouble using them.

 

[JanH]

Amplifiers usage is not so easy. There are limitations which can make problem. One is maximum signal output level which amplifier is able manage. If signal is bigger then cross modulation destroy the signal and quality include S/N going down. It is why not possible to connect amplifier near LNB. Usage on recever input is for nothing too because input noise of receiver may be better then amplifier or same. Big signal can congest tuner too. Only way is to use amplifier in the middle of attenuation. It could be cable and some divider, outlet etc. which make signal losses.

 

[mouse3]

I found on Your country forum one 4m dish for testing,it s full of reception raport there.It s impressive this dx club.
Today the best LNC ever it s the Invero Black Ultra.Using them i found only good surprise.I dont know if the same brand in line amplifiers are available on the market.I ask here but the replay it was no.

 

[mouse3]

Talking about dishes at home,one dx report,one guy from my country make at home one 4,2m dish for C band.
Intresting catch,Thaicom and Asiasat 5.The dish perform like 3m+, it s the only one to catch in my contry this tv channels.

 

[fta-elite]

Hi Mouse3

Do you know how this guy made this antenna?
Looks like my antenna.

fta-elite

 

[mouse3]

Hi Mouse3

Do you know how this guy made this antenna?
Looks like my antenna.

fta-elite

Work hard to finish the project,i have samwhere on database one picture with parabolic frame under construction.
If i remember well your s dish it s 1,8m this guy make 4,2m.The petals are made from 0,6mm aluminium.I found the post on my country forum,the project it s two years old,if you want i give you the name,page ant where to found details.The language it s in Romanian,if you speak Italian it s fine,you understand well.

 

[fta-elite]

Thanks Mouse3, I sent to you a PM.

Regards

fta-elite

 

[mouse3]

Yes,you have the replay.
I found samthing intresting about fresnel C band parabolic antenna to build at home.Looks intresting for one future experiment.The gain don t match the parabolics but are flat and more easy to buid one,i think.

 

[JanH]

Some photos from cooling experiment.

 

[JanH]

See in this section:
Thread: 8m dish in Brazil receiving Astra/Hotbird
Who is better :-)

 

[Captain Jack]

What signal gains did you get from cooling your LNB?