Is it possible to increase the size of an offset dish?

D

DishDick

Regular Member
Messages
772
My Satellite Setup
.
My Location
Gran Canaria
Dear All,

I know you can add petals to prime focus dishes to increase their reception area, but is it possible to add petals to an offset dish to increase their reception area? I ask as I would like to try and attempt to get some of the missing vertical transponders. I am lucky that one of my neighbours used to have an engineering company and would welcome a challenge.

I thought that adding 30 cm all round (making dish 3.6 x 3.3m) could be done by using a section of the current outer 30 cm to make the mould, then making 8 petals that clipped onto the side of the dish. Thus the curve of the dish would be maintained.

Thoughts please.
 
Analoguesat

Analoguesat

Administrator
Staff member
Messages
47,866
Location
Scottish Borders
My Satellite Setup
TM 5402HD
Skybox F3
Sky+ UK.
My Location
Scottish Borders
You would be wasting your time - the lnb focal length is engineered to illuminate the manufactured dish size. You can add as much metalwork as you liked - the lnb wouldnt see any more.
 
Zorba

Zorba

Regular Member
Messages
2,201
My Satellite Setup
3m(28.2E),1.5m(19.2E.13E,10E),1m (4W ,7W)1m (?).diseqc 10,sky plus,VU+,telergy iptv.
Satlook nit colour + Horizon hdsm.
My Location
Limassol, Sunny Cyprus
What if you moved the lnb out more in proportion to the area expansion?
 
rolfw

rolfw

Believe it when I see it Admin.
Staff member
Messages
37,928
My Satellite Setup
Technomate 5402 HD M2 Ci, DM7000s, Transparent 80cm Dish, Moteck SG2100 DiseqC motor, lots of legacy gear. Meters: Satlook Digital NIT, Promax HD Ranger+ spectrum analyser.
My Location
Berkshire
I you moved the LNB out, you would lose focus on the original part of the dish.
 
Robbo

Robbo

Retired Mod
Messages
6,424
My Satellite Setup
TM6800HD, TM1000, TM600 Linux,TM2200 motor, Channel Master 1.2m motorised, TD110 dish Meter=Satlook Micro+G2 NIT
My Location
Gravesend,Kent,UK
If the dish were bigger, and the focal point the same as it is now, as AS says the standard LNB would not see the extensions, without a different feedhorn, with a lower F/D.

However, I think the biggest problem would be to get the extentions the right shape, making a mold from part of the existing dish wouldn't work, the offset dish is part of a hypothetical very much larger prime focus dish.
 
Telia

Telia

ASBO Club Member - Persona non grata
Messages
335
My Satellite Setup
Vu+ Duo PVR 1GB HDD
Channel Master 1.2m with Jaeger SMR1224.
My Location
Stockholm, Sweden
I tried this once on a 90cm dish, i added CDs all around the dish rim, i actually got about 0.5dB more signal.
 
Topper

Topper

Amo Amas Amant Admin
Staff member
Messages
22,832
My Satellite Setup
IDD CI24 ECONO MM Penta 1.20 Galaxy II
1.2Mtr Polar MTG yes it has been on the arc for 25 years and is now fixed on 13 East using two pairs of rusty molegrips. Unlike me they never groan but always perform.
My Location
Blackburn, Lancashire
Telia said:
I tried this once on a 90cm dish, i added CDs all around the dish rim, i actually got about 0.5dB more signal.
Well that was lucky....... but i'll bet your your dish ended up looking a bit like a pansy or should that be a daisy
 
T_G

T_G

The Consumate Dreamer
Staff member
Messages
6,664
My Satellite Setup
1 GigaBlue Quad plus, 1 Dreambox 5620, MOTECK SG2100A DISEqC Motor, 120 cm noname offset dish, Humax 95 cm offset dish and a few UK digiboxes.
My Location
Somewhere where the Sauer is Kraut and the Wurst is Brat
Making all the moulds, and then attaching them in such an accurare manner that they all focus to the correct point, and then fiddling with the LNB is more or less doomed. It will cost a lot of time and materials, and most likely the first samples will have to be remade until you learn from it. I have done a lot of work oncarbon fibre and glass fibre moulding - it never works out the first time.

If you have the time and money and the engineering possibilities, why don't you go and build a completely new large dish, that would probably have a better chance. we got a good thread about this here.
 
J

JanH

Regular Member
Messages
80
My Satellite Setup
Dreambox 800
My Location
Czech rep.
I perfectly agree that it is wasting time to make ready use offset dish biger. Another problem is that offset dish is not quite parabolic and dish should be exact round millimeters.

What do you think about other idea.
Next to original dish put second similar dish. To focal point of the second one could be fasten reflector instead LNB which is pointed to midle of first dish.
Signal phase could be set up by dishes distance.
 
E

essao

New Member
Messages
1
My Satellite Setup
v7combo 135cm dish
My Location
kenya
Well that was lucky....... but i'll bet your your dish ended up looking a bit like a pansy or should that be a daisy
hi...do you have pictures of this experiment?
 
Channel Hopper

Channel Hopper

Suffering fools, so you don't have to.
Staff member
Messages
29,667
My Satellite Setup
A little less analogue, and a lot more crap.
My Location
UK
hi...do you have pictures of this experiment?
Not for an offset dish, but check the threads for Vipersan and Christine.
 
Topper

Topper

Amo Amas Amant Admin
Staff member
Messages
22,832
My Satellite Setup
IDD CI24 ECONO MM Penta 1.20 Galaxy II
1.2Mtr Polar MTG yes it has been on the arc for 25 years and is now fixed on 13 East using two pairs of rusty molegrips. Unlike me they never groan but always perform.
My Location
Blackburn, Lancashire
hi...do you have pictures of this experiment?
Not for an offset only a prime focus dish
 
Top