Anyone tried to make BIG dish at home?

[pride21]

hi all pics of wooden dish i made a couple of years ago,i made it into four sections that could be bolted together.

[divibi]

If you are striving for pefection and trying to get weak signals, then pefection is needed. But you can also do it the way american car manufacurers used to do: Instead of cultivating a small sport engine they just added more volume...

Yes, perfection is needed, especially in KU band. In C-band you can get away with a lot of imprecision.

[divibi]

divibi, you may not know, but a lot of people do at home parabolic reflectors for telescopes (of course not 2m, but 50-60cm), and they achieve micrometre accuracy, not mm

Hi BombedOne,

Thanks very much for very good info. I didn't know about MICROMETRE accuracy that they achieve. Do they use lasers to check the accuracy and wear magnifying glasses like watchmakers and jewellers? You've just given me hope it's possible to make a 1m dish that has the same gain as 1.80m one. Just imagine what dish gain those micrometres could give you!!!

[pedro2000uk]

hi all pics of wooden dish i made a couple of years ago,i made it into four sections that could be bolted together.

Amazing... so how well did it actually do...?

[BombedOne]

Sorry, divibi, you misunderstood me. Micrometre precision is needed when dealing with waves, much much shorter than ones in Ku band (visible light), and regardless how well you polish your dish, antenna gain can't increase above certain level - which is directly related to dish size. So you'll have to do big dish in any cases.

[koansrc]

AMAZING! Great pictures, if anyone else got some more of the same subject please post them. I really like them home made dishes!

Here's my attempt. Not quite a "big dish" ...

http://www.satellites.co.uk/satellit...tml#post732855

and here's how :

http://www.satellites.co.uk/satellit...tml#post731602

[divibi]

The real problem is, book doesn't mentions quantity of fiberglass and epoxy needed even for 2 meter model (trough it says - 5 or 6 layers will be needed). So if it really needs large amount, maybe manufacturing will be expensive, than buying ready one. For test purposes, I bought 0.5kg of epoxy and 1x1m sheet of fiberglass fabric. This weekend I'll try to reproduce small scale (20-30cm) model, just to check manufacturing problem/expenses, I will not target parabolic shape, just will use beach ball as preform.

Hello,

Did you make that small scale model? Does it work and what do you estimate the costs to be for a 60 cm, 1m, 2m dishes? Thanks in advance.

[BombedOne]

No I still don't, too much work these days. But will do it asap.

[casser]

Nice to see a couple of homemade antennas..

what is the expected efficiency of those antennas?

I´m not a dish guy...i prefer waveguide antennas At this moment i´m testing a multibeam homemade antenna, but with 24dBi i´m only getting 18% of signal...i was expecting 40%

[Satcom1]

Hello Everyone,

This subject is of great interest to me. I found a little program that designs the parabola for you and is very easy to do "What If". You can match f/d to diameter and depth. It is called Parabola Calculator V 1.0 and you can Google it.
I was thinking of using a sand box and a screed board with the shape of the parabola. By using damp sand a very smooth surface is made. Once the surface was defined a Urethane plastisizer would be sprayed on with spray bottle. The Urethane hardens in contact with water. A layer of aluminum window screen is applied. Or, layers of fine woven glass cloth would build up. Once set hard and removed the back or mold side would be sanded smooth and Copper Leaf would be applied.

A sand mix concrete mixed somewhat dry could be used instead of the sand.

_http://www.educypedia.be/electronics/easoftrf.htm
This is the link for the parabola calculator.


I've attached a project report.

[divibi]

Nice to see a couple of homemade antennas..

what is the expected efficiency of those antennas?

I´m not a dish guy...i prefer waveguide antennas At this moment i´m testing a multibeam homemade antenna, but with 24dBi i´m only getting 18% of signal...i was expecting 40%

Hi casser,

Nice to see you in this section. I read your post in pictures of members' setups.. I must say it blew my mind how creative you are. I liked the pictures of your umbrella dishes. That mesh umbrella with 2 lnb's, what are those lnb's? Are waveguide antennas more tolerant of imprecision and inaccuracy? Could I be 1cm off without dramatically affecting the gain? So 40cm diametre conical antenna is 260cm long, but it performs like a 70cm offset dish??? If I ever built WALK-IN TYPE OF CONES how long would they be - 50 metres long?

I can only say that for KU-band dish antennas you need 1mm precision. If you can achieve that 1mm accuracy then you got yourself a COMMERCIAL GRADE dish and the efficiency is the same you'll find in textbooks and articles.

[divibi]

Hello Everyone,

This subject is of great interest to me. I found a little program that designs the parabola for you and is very easy to do "What If". You can match f/d to diameter and depth. It is called Parabola Calculator V 1.0 and you can Google it.
I was thinking of using a sand box and a screed board with the shape of the parabola. By using damp sand a very smooth surface is made. Once the surface was defined a Urethane plastisizer would be sprayed on with spray bottle. The Urethane hardens in contact with water. A layer of aluminum window screen is applied. Or, layers of fine woven glass cloth would build up. Once set hard and removed the back or mold side would be sanded smooth and Copper Leaf would be applied.

A sand mix concrete mixed somewhat dry could be used instead of the sand.

Hi Satcom1,

Welcome to the forum!!! Thank you very much for sharing with us your preferred method of making a dish. Slowly but surely by reading all the posts here I'm building a picture of how it all may just work with a great deal of precision down to the millimeter. What is aluminum window screen?

[casser]

Hi casser,

Nice to see you in this section. I read your post in pictures of members' setups.. I must say it blew my mind how creative you are. I liked the pictures of your umbrella dishes. That mesh umbrella with 2 lnb's, what are those lnb's? Are waveguide antennas more tolerant of imprecision and inaccuracy? Could I be 1cm off without dramatically affecting the gain? So 40cm diametre conical antenna is 260cm long, but it performs like a 70cm offset dish??? If I ever built WALK-IN TYPE OF CONES how long would they be - 50 metres long?

I can only say that for KU-band dish antennas you need 1mm precision. If you can achieve that 1mm accuracy then you got yourself a COMMERCIAL GRADE dish and the efficiency is the same you'll find in textbooks and articles.

If you don't mind me asking; maybe you are located in Azores or know anyone from there who can receive Echostar satellite at 61.5 west with American package- Dish Network? Or anybody receiving Canadian packages? Can you also receive proper BRAZILIAN C-band satellites? Thank you in advance.

Hi divibi..

If you´re refering to the mesh umbrella in this topic, that´s a umbrella made for 2.4Ghz (WIFI), you can see there is a USB Adapter in the focal point. That umbrella it´s not mine.

Without lying, i have build more than 20 conical horn´s antennas and i can say for sure, that a Conical Horn antenna is not critical for 1mm construction that we should expect in these frequencies...you can see here-->_http://img373.imageshack.us/img373/746/semttulois9qv7.jpg, some of my simulations to conical horn´s...variations of 10/20mm dont do much in a conical horn. I joke saying "size? doesnt matter, the waves will enter in the cone and find the way to the LNB"

Conical Horn´s and antennas like DigiDish/Selfsat/Arcon need less gain to outperform a offset dish with bigger gain... that´s why i prefer the waveguides, parabolic dish need 1mm precision like you said...it´s very difficult to achieve that using homemade material´s. But >32dBi Conical Horn, the lenght of the horn it get´s unpracticable..i dont remember for sure, but i think that a 36dBi conical horn will be 6meter long.


Yes, i´m from Azores I dont know anyone that can receive any American C/Ku Band satellites..but that´s an interesting idea! I believe that´s possible..

[divibi]

Thanks everyone for reply.

Regarding method I've read in book. It has drawing for making specially cutted out metal plate, which you install on tube, to allow 360 degree rotation over center axis, and you use it to create preform from concrete and (or) clay. Below I tried to reproduce drawing from it:

_http://img329.imageshack.us/my.php?image=dishov4.jpg

First you make metal plate (The formula I mentioned defines it's shape calculation, and book already contains design for 2m dish plate), then mount it on stable pole. Then build pyramid like construction around of it made from bricks or stones. After that - roughly apply concrete, and start using metal plate to achieve exact form. For finishing touches, modelling clay is recomended. Regarding reflecting layer, it should be made from aluminum foil.

Is that what is called a POSITIVE mould?

[BombedOne]

Today I went to building materials store, and I think I found a source for fiberglass dish. I don't know how to name it in english (it is used during plastering works on non-flat surfaces, to support plaster material), it's a special tape, in rolls, made of fiberglass. It has anti mosquitto net like structure, but crossed lines aren't connected in their joints, so stripe can be deformed more freely. Only disadvantage is, that size of "cells" was too high, about 8x8mm, but salesman said, that there's exist more dense variations of that tape, and warned, that some models are made from plastic, not fiberglass.

Next days I'll try to find one with desired parameters. I believe, using stripes, instead of solid mesh of fiberglass cloth, during dish construction, will make work much more easier.

[divibi]

Today I went to building materials store, and I think I found a source for fiberglass dish. I don't know how to name it in english (it is used during plastering works on non-flat surfaces, to support plaster material), it's a special tape, in rolls, made of fiberglass. It has anti mosquitto net like structure, but crossed lines aren't connected in their joints, so stripe can be deformed more freely. Only disadvantage is, that size of "cells" was too high, about 8x8mm, but salesman said, that there's exist more dense variations of that tape, and warned, that some models are made from plastic, not fiberglass.

Maybe it's called plasterboard tape???
BombedOne, is the preform built partly with bricks stacked in a pyramid-like structure what they call a POSITIVE MOULD? Do you know how Klaus Schumacher built his 8m dish? There are 2 clips on youtube 'Astra in Brazil'. They say he used a NEGATIVE MOULD made of concrete. I don't understand which is which.

[pedro2000uk]

that is plasterboard jointing tape used to avoid plaster cracks on joints and is quite strong.. whether it is OK I would say maybe to add strength on the back of the dish and help add webbing.

[BombedOne]

Yes it may be positive. There are several advantages of both kind of moulds:

Positive: Provides better quality of reflective surface, but hard to made in large sizes.

Negative: Has worse quality of reflective surface, but easier to made in large sizes.

[Satcom1]

Hi Satcom1,

Welcome to the forum!!! Thank you very much for sharing with us your preferred method of making a dish. Slowly but surely by reading all the posts here I'm building a picture of how it all may just work with a great deal of precision down to the millimeter. What is aluminum window screen?

Hi divibi;

Very interesting post about the Umbrella antenna. I was in Farm & Fleet the other day and found a golfer's umbrella with a fiberglass mast. It was 2 meters wide and I almost bought it for an experimental dish. If I could get my hands on very fine mesh, I would try this. Can you post to me the link for the umbrella dish?

In USA most screen windows are fiberglass but they still sell aluminum window screen (BUG screen) about 2 meters by 1 meter roll for $8USD. By itself it shapes and contours very nicely and is an open mesh of about 1 mm square. Back in the 1940's most window screen was made of copper.

Yes, I read somwhere that the dish surface tolerence should be within 1 mm at KU band.

[Satcom1]

Hello divibi -

I found the information about the Umbrella Dish interesting. I was at Farm & Fleet (Large general merchandise store) and found a 2 meter umbrella with fiberglass mast. I almost bought it to experiment with. After reading this other thread and the poor efficiencies I'll pass.

In USA (Bug Screen) is now made of fiberglass but in the 1970's it was made of Aluminum and is a woven metal cloth with 1 mm square openings. In the 1940"s it was made of copper. You can still buy Aluminum screen in 2 meter by 1 meter rolls for $8 USD. It molds to shape very nicely.

Cheers

[divibi]

Very interesting post about the Umbrella antenna. I was in Farm & Fleet the other day and found a golfer's umbrella with a fiberglass mast. It was 2 meters wide and I almost bought it for an experimental dish. If I could get my hands on very fine mesh, I would try this. Can you post to me the link for the umbrella dish?

Hi
It is Casser who knows about umbrella dishes. His post is on this page. post number 63. In it you'll find a blue highlighted topic link. Those umbrella dishes are for wi-Fi. Thanks for the info about bug screens.

[casser]

Hi
It is Casser who knows about umbrella dishes. His post is on this page. post number 63. In it you'll find a blue highlighted topic link. Those umbrella dishes are for wi-Fi. Thanks for the info about bug screens.

Umbrellas doesn´t have a perfect parabolic shape...but i have seen a Carlberg "sun umbrellas" (i dont know the correct name) with +-1.8meter

In the attachments files i have a 500mm parabolic shape with a F/D of 0.25...giving a focal point of 125mm. That antenna have 32.8dBi with a efficiency of 50%. "Half"--> print in A4 paper (print two of them, cut, an join the two half parabolic shapes); Intire-->print in A2 paper.


Since many people are interested in building their own antenna, why dont we "study" a Tecnhisat antenna...a 45cms version perform better than a 60cm version. Or even a Arcon Multi 57cm that perform´s better than a 80cm dish..

If we find the patent´s of those antennas, we have all the information to build one or we can try to find some paper´s related to that kind of antennas in ieeexplore.ieee.org.

[divibi]

Since many people are interested in building their own antenna, why dont we "study" a Tecnhisat antenna...a 45cms version perform better than a 60cm version. Or even a Arcon Multi 57cm that perform´s better than a 80cm dish..

If we find the patent´s of those antennas, we have all the information to build one or we can try to find some paper´s related to that kind of antennas in ieeexplore.ieee.org.

Hi

It is a very good idea. There is something special about those anntennas you mentioned; the precision must be incredible. At the moment I'm trying to get the knowledge of how to achieve 1mm accuracy. Today I'll be searching for answers.

[BombedOne]

There's only one way to achieve such precision - use power of rotation - just look how precise round ancient clay dishes are...

[Satcom1]

There's only one way to achieve such precision - use power of rotation - just look how precise round ancient clay dishes are...

Yes, this is very true. I watched a show on the Science Channel here called "How It's Made". They showed a man working a flat aluminum plate into a deep drawn metal pot with a lathe and a tool with a roller on the end of it.

I have also seen very precise large dishes made of metal using an explosive charge located about 1 meter above the plate.