Anyone tried to make BIG dish at home?

franksanderdo

Member
Joined
Aug 31, 2010
Messages
13
Reaction score
0
Points
0
Age
55
My Satellite Setup
2m PFA
Invacom TWFH031
DM800HD S
AZBox Premium S
Mac Book Pro
My Location
Saudi Arabia East Coast
Hi and Hello,

well, some test further I can say:
1. The "Focus" of the Dish is about 9 cm closer to the Dish than the original support suggests ;-)
2. To talk about Focus is some how exaggerating. it is more a 10cm2 area.
3. With a quickly produced template I learned the shape of the Dish is some what round but far away from parapolic :-)
4. Lessons learned and preparing to build my own one.

Keep trying guys
Frank
 

dante2

Member
Joined
Oct 19, 2005
Messages
2
Reaction score
0
Points
0
Age
52
My Satellite Setup
Digital receivers: Mediamaster 9600, d-box1, Clarke-Tech 1500 Plus, Skystar1 rev. 1.3;
LNB: 2xInverto 0.3dB, Panorama C-band 13 kelvin;
Dish: 2x1.8m primefocus, Prodelin 1.4m offset;
Diseqc 1.2 positioners
My Location
Transilvania
Congratulations! Great job!
Yet, I have a small observation: I think is not sure that this form is a parabola, also can be a catenary.
_http://en.wikipedia.org/wiki/Catenary]Catenary - Wikipedia, the free encyclopedia
_http://www.carondelet.pvt.k12.ca.us/Family/Math/03210/page5.htm]Parabolas in Suspension Bridges! Oh, my!
_http://personal.strath.ac.uk/j.wood/Biomimetics/Engineering%20Areas/structures/STRUCTURES.htm]STRUCTURES
I also want to build a large dish at home, so I will continue to investigate this phenomenon.
 

JanH

Regular Member
Joined
Apr 23, 2009
Messages
80
Reaction score
0
Points
0
Age
65
My Satellite Setup
Dreambox 800
My Location
Czech rep.
"Therefore, the cables of a suspension bridge is a parabola, because the weight of the deck is equally distributed on the curve."

"When the structure is being built and the main cables are attached to the towers, the curve is a catenary."

I can not see difference between these two definitions and also can not imagine other curve similar parabolic with one focal point. Main cables still have weight equally distributed
on the curve with or without bridge. Probably bridge have not weight equally distributed.
It is shortcut.

I think same princip used discussed membrane parabolic.

What the point of the catenary usage?
 

JanH

Regular Member
Joined
Apr 23, 2009
Messages
80
Reaction score
0
Points
0
Age
65
My Satellite Setup
Dreambox 800
My Location
Czech rep.
franksanderdo said:
Hi and Hello,

well, some test further I can say:
1. The "Focus" of the Dish is about 9 cm closer to the Dish than the original support suggests ;-)
2. To talk about Focus is some how exaggerating. it is more a 10cm2 area.
3. With a quickly produced template I learned the shape of the Dish is some what round but far away from parapolic :-)
4. Lessons learned and preparing to build my own one.

Keep trying guys
Frank


Anything new Frank?
 

PaulR

Dazed and Confused Admin
Staff member
Joined
Jun 28, 2003
Messages
18,055
Reaction score
4,071
Points
113
My Satellite Setup
-----------See sig-----------
My Location
Wirral, NW UK and Vaucluse, France.
JanH said:
I can not see difference between these two definitions and also can not imagine other curve similar parabolic with one focal point.
It's a bit mathematical but have a read of this _http://whistleralley.com/hanging/hanging.htm
 

Satcom1

Regular Member
Joined
Sep 20, 2008
Messages
217
Reaction score
3
Points
0
Age
52
My Satellite Setup
1 Meter Primestar Elliptical C/KU. Twinhan 1025 PCI(Linux), Coolsat 6000, Winegard 76 cm dish. 8' Unimesh, HCC9300 Receiver.
Diamond 9000 HD, 1m prime focus, 1.2 m prime focus, both on C Band.
My Location
Chicago
This example defines ray trace between the parabola and catenary. LNBF focus can be assumed better with a parabola.

However, I have found that offset dishes tend to be catenary while prime focus are parabolic.:-gnome
 

Attachments

  • Catenary Solar Cookers.pdf
    842.7 KB · Views: 108

Channel Hopper

Suffering fools, so you don't have to.
Staff member
Joined
Jan 1, 2000
Messages
35,991
Reaction score
8,712
Points
113
Age
60
Website
www.sat-elite.uk
My Satellite Setup
A little less analogue, and a lot more crap.
My Location
UK
From memory a catenary curve (apart from being two dimensional) has no single focal point that can be derived within the equation.
 

PaulR

Dazed and Confused Admin
Staff member
Joined
Jun 28, 2003
Messages
18,055
Reaction score
4,071
Points
113
My Satellite Setup
-----------See sig-----------
My Location
Wirral, NW UK and Vaucluse, France.
Agreed with you CH. This is why it's OK to use a catenary for a cooker as it doesn't matter if the focal point is diffused.

Satcom1 - where did you find that offset dishes are a catenary? I was under the impression that they were an angled slice through a parabolic.
 

Channel Hopper

Suffering fools, so you don't have to.
Staff member
Joined
Jan 1, 2000
Messages
35,991
Reaction score
8,712
Points
113
Age
60
Website
www.sat-elite.uk
My Satellite Setup
A little less analogue, and a lot more crap.
My Location
UK
PaulR said:
Agreed with you CH. This is why it's OK to use a catenary for a cooker as it doesn't matter if the focal point is diffused.

Satcom1 - where did you find that offset dishes are a catenary? I was under the impression that they were an angled slice through a parabolic.

Two earlier posts on the page mentioned caternary in their answers.

For solar cookers it is important that there is no distinct focal point otherwise hot spots occur, leading to burnt food and reduced life of the cooker.
 

JanH

Regular Member
Joined
Apr 23, 2009
Messages
80
Reaction score
0
Points
0
Age
65
My Satellite Setup
Dreambox 800
My Location
Czech rep.
Looks like to me that catenary is similar parabolic with some difference what make less efficiency (for sat. antenne). Vacuum or presure antenne mentioned above should be catenary not a parabolic curve. It I figure out from the material above if it is right.
Cooker for shure do not need small focus point more likely with size of cup -:)
 

Satcom1

Regular Member
Joined
Sep 20, 2008
Messages
217
Reaction score
3
Points
0
Age
52
My Satellite Setup
1 Meter Primestar Elliptical C/KU. Twinhan 1025 PCI(Linux), Coolsat 6000, Winegard 76 cm dish. 8' Unimesh, HCC9300 Receiver.
Diamond 9000 HD, 1m prime focus, 1.2 m prime focus, both on C Band.
My Location
Chicago
PaulR said:
Agreed with you CH. This is why it's OK to use a catenary for a cooker as it doesn't matter if the focal point is diffused.

Satcom1 - where did you find that offset dishes are a catenary? I was under the impression that they were an angled slice through a parabolic.

Yes, I believe that an offset starts out as an offset section of a larger true parabola. However, measurements of Winegard dishes have their horizontal edges tipped in from a perfect parabola. I understand that their may be an attempt to improve issues with cross polarization that all offsets have. As you know no design is perfect and there are always trade offs in the design. Where focus may be sacrificed for improvement of signal to noise.
 

Channel Hopper

Suffering fools, so you don't have to.
Staff member
Joined
Jan 1, 2000
Messages
35,991
Reaction score
8,712
Points
113
Age
60
Website
www.sat-elite.uk
My Satellite Setup
A little less analogue, and a lot more crap.
My Location
UK
Satcom1 said:
Yes, I believe that an offset starts out as an offset section of a larger true parabola. However, measurements of Winegard dishes have their horizontal edges tipped in from a perfect parabola. I understand that their may be an attempt to improve issues with cross polarization that all offsets have. As you know no design is perfect and there are always trade offs in the design. Where focus may be sacrificed for improvement of signal to noise.

There is every chance someone was matching the reflector design to a combination of feed systems, over a number of bands.
Or it could just be a failure in the original design blueprints.
 

JanH

Regular Member
Joined
Apr 23, 2009
Messages
80
Reaction score
0
Points
0
Age
65
My Satellite Setup
Dreambox 800
My Location
Czech rep.
Offset dish designer should solve problem that feedhorn can see whole parabolic not only a cated part. Missing parabolic but "visible" section make noise and decrase effectivness as well as make problems with feedhorn/dish impedance.
It is why feedhorn is not pointed to centre of virtual parabolic but somwhere to centre of offset disch. Offset dish should not be parabolic or catenary but special curve based of parabolic.
 

PaulR

Dazed and Confused Admin
Staff member
Joined
Jun 28, 2003
Messages
18,055
Reaction score
4,071
Points
113
My Satellite Setup
-----------See sig-----------
My Location
Wirral, NW UK and Vaucluse, France.
JanH said:
Offset dish should not be parabolic or catenary but special curve based of parabolic.
As I said!

PaulR said:
they were an angled slice through a parabolic.
 

JanH

Regular Member
Joined
Apr 23, 2009
Messages
80
Reaction score
0
Points
0
Age
65
My Satellite Setup
Dreambox 800
My Location
Czech rep.
Nice, we are two :-)

Who is against the idea?
 

PaulR

Dazed and Confused Admin
Staff member
Joined
Jun 28, 2003
Messages
18,055
Reaction score
4,071
Points
113
My Satellite Setup
-----------See sig-----------
My Location
Wirral, NW UK and Vaucluse, France.
Satcom1 has posted that he has found that some off-set dishes are not.

Satcom1 said:
However, I have found that offset dishes tend to be catenary while prime focus are parabolic.:-gnome
 

fta-elite

Member
Joined
Mar 3, 2011
Messages
15
Reaction score
0
Points
0
Age
62
My Satellite Setup
Sonicview 360 Elite, 90cm and homemade 1.80 antennas
My Location
Colombia
hello everyone

I new in this forum, I read the whole thread and it´s very interesting, I made my own home dish and I want to know your opinion.


Best regards
 

Attachments

  • ParaSegment.jpg
    ParaSegment.jpg
    209.5 KB · Views: 187
  • AntenaFinal4.JPG
    AntenaFinal4.JPG
    602.1 KB · Views: 234
  • IMG_0207.JPG
    IMG_0207.JPG
    557.8 KB · Views: 220

franksanderdo

Member
Joined
Aug 31, 2010
Messages
13
Reaction score
0
Points
0
Age
55
My Satellite Setup
2m PFA
Invacom TWFH031
DM800HD S
AZBox Premium S
Mac Book Pro
My Location
Saudi Arabia East Coast
Hi fta-elite,

this looks like an interesting approach.
Especially for C Band I believe it is very good.
Can you give some description how you made it?
Which Materials have been used?
Do I read the drawing right that the dish is +- 2m dia?

Well done!!

See you around
Frank
 

PaulR

Dazed and Confused Admin
Staff member
Joined
Jun 28, 2003
Messages
18,055
Reaction score
4,071
Points
113
My Satellite Setup
-----------See sig-----------
My Location
Wirral, NW UK and Vaucluse, France.
What a great bit of work there. It won't work on Ku band but for C band - fantastic.
 

Vipersan

Emmett Browns Ghost
Joined
Jun 29, 2009
Messages
10,918
Reaction score
6,663
Points
113
Age
67
My Satellite Setup
IP9000HD +
TD110 Dish and TD88 Dish in Tandem
66°East to 60°West.
AZbox PrmHD + OpnbxS9HD + Skybox + DrHD F15
2x VboxII AZ-EL
2 m+ Alcoa PF + BSC421 C-Band lnbf...
+SS2/TwHnS2-3200 pci/TBS6925 pci
1.5 Fortec Star -Gbox - HtoH Ku/Ka/C
My Location
UK
Very Impressive work m8 ..
I do love it when ingenuity Is displayed accompanied by obvious talent..
This board abounds with such creative types..
certainly count yourself amongst them.

As has been said already ..
I doubt the construct is accurate enough for KU fringe work ..
..but for C band (a passion of mine) ...I suspect it will perform well.
rgds
VS
 
Top