Anyone tried to make BIG dish at home?

[guest poster]

.........I didint understand the oblong cone.........

thanks casser,

instead of a round cone ... oblong..... like many pro' waveguides ....

also, can conical antennas be coiled in a spiral shape etc...?

I understand that there can be problems with picking up adjacent satellites, is that a very big problem?

cheers ...

 

[casser]

I'm not following you... 5.5m is the diameter of the opening of the horn or the lenght of it?

5.5meter is the conical horn diameter (opening horn, mouth)..412meter is the lenght of the horn.

thanks casser,

instead of a round cone ... oblong..... like many pro' waveguides ....

also, can conical antennas be coiled in a spiral shape etc...?

I understand that there can be problems with picking up adjacent satellites, is that a very big problem?

cheers ...

Oblong conical horn´s never heard about it...also it should be complicated to construct a oblong shape of the mouth to the oval shape of the waveguide. But i know that elliptical conical horn have +- the same gain of a oval conical horn (1º attached image)..sometimes i squeeze the conical horn to a elliptical shape and got the same results.

There are a lot of variations of conical horn´s, but one particular conical horn (Conical Horn reflector) should be perfect..

-Have the same +3dB performance
-The length of the conical horn is +- 2x the diameter


_http://www.afcsat.com/SatelliteConicalHorn.html
_http://www.ntia.doc.gov/osmhome/reports/bath/antennas.pdf

Images
_http://long-lines.net/places-routes/Garden_City/010221B-17A.jpg
_http://long-lines.net/places-routes/Garden_City/010221B-19A.jpg
_http://long-lines.net/places-routes/Garden_City/010221B-07A.jpg
_http://www.nps.gov/history/history/online_books/butowsky5/astro4k.htm

Brief explanation about the antenna:
_http://books.google.pt/books?id=njTri1942n4C&pg=PA257&dq=%22horn+reflector+antenna%22#PPA257,M1 (page 257)

Patents:
_http://www.google.com/patents?id=f34zAAAAEBAJ&printsec=abstract&zoom=4&dq=PYRAMIDAL+conical+HORN+REFLECTOR+ANTENNA#PPA2,M1
_http://www.google.com/patents?id=26dzAAAAEBAJ&printsec=abstract&zoom=4&dq=PYRAMIDAL+HORN+REFLECTOR+ANTENNA#PPA2,M


But it´s too much complicated for me

 

[kamaleon]

5.5meter is the conical horn diameter (opening horn, mouth)..412meter is the lenght of the horn.

Bugger then

 

[guest poster]

Great links ... Casser.... thanks..!

I remember now it was the big horn antennas of the 60s I was thinking of regarding 'oblong' and they can be sent round a bend then...

I'm not so sure they are that suitable for KU ... but maybe favour C band or lower frequencies... what do you think...?

One of those links (_http://www.afcsat.com/SatelliteConicalHorn.html) demonstrate the ground noise and local interference issues which they highlight their horn antennas have have much lower noise (temp) than satellite dishes .. (particularly offset)

all really interesting stuff...

thanks ..!!

 

[casser]

Bugger then

Like i said before, conical horn´s are really looonnnng

Great links ... Casser.... thanks..!

I remember now it was the big horn antennas of the 60s I was thinking of regarding 'oblong' and they can be sent round a bend then...

I'm not so sure they are that suitable for KU ... but maybe favour C band or lower frequencies... what do you think...?

One of those links (_http://www.afcsat.com/SatelliteConicalHorn.html) demonstrate the ground noise and local interference issues which they highlight their horn antennas have have much lower noise (temp) than satellite dishes .. (particularly offset)

all really interesting stuff...

thanks ..!!

In the AFC page, they mention on the 3dB gain over a dish " The lower noise temperature improves G/T signal and picture quality typically 3 dB"..but for what i understand until now, the reflector on that Conical Horn is based on a Offset dish...if it´s hard to do a simple parabola, i dont know how we going to make a offset reflector

but i´m still working in my own reflector design for "print, cut, mount" homemade antenna

This 80cm version it´s made from Styrofoam and aluminium tape on the back..the antenna was made from leftover´s and i was not patient enough to do the correct dimensions, so instead of 50mm depth i got 65mm depth:mad:

Also the LNB is not centered...the antenna is aiming +-10º from it should be and the elevation looks like 0º instead of 35º. It´s working like a 45/50cm dish..i need to center the LNB someway.

mobile phone pictures at night...

 

[BombedOne]

Do you need offset dish calculation formulas? I have excell preset somewhere...

 

[divibi]

Hi,

How do they do it???
I am asking again because that is the way to go and self build one's own dish, I think. We need accuracy.

 

[BombedOne]

DO you really need perfect, but 40-60cm sized dish?

google for "homemade parabolic reflector"

 

[casser]

Do you need offset dish calculation formulas? I have excell preset somewhere...

Thanks, but only few weeks from now i will try to make the Conical Horn Reflector. Later i´ll ask for it.

Yesterday i went to my university and run some antennas..

-The 80cm version (photos in my earlier post):

35.7dBi at 11.75Ghz (38% efficiency)(-red), almost 3dBi less than a good Offset dish...VSWR 1.8 max, i need to work on a better version.


Also i try the Fresnel "Satcom1" antenna, i didint know the dimensions for the antenna..so i guess, result..

30.2dBi at 4Ghz (30.32% efficiency), didint see anything that could justify the bad result that "Satcom1" said..but i´m no expert

 

[guest poster]

Do you need offset dish calculation formulas? I have excell preset somewhere...

I would like to see that BombedOne...

 

[Moradabad]

Do you need offset dish calculation formulas? I have excell preset somewhere...

Can you provide me that formula for offset feed:-worship

 

[BombedOne]

The formulas can be downloaded from here:

_ttp://satcat.nm.ru/parab-ant.dhtml

 

[guest poster]

The formulas can be downloaded from here:

_ttp://satcat.nm.ru/parab-ant.dhtml

hi Bombedone.....

couldn't get the link to work -... any chance to just type the equation.. we have our own for offset and it would be interesting to compare anyway.


cheers

 

[kamaleon]

Try here:

_http://satcat.nm.ru/files/ParabAnt.rar
_http://satcat.nm.ru/files/ParabAnt-v2.rar

 

[Moradabad]

this all are are in russian thats the main issue

 

[kamaleon]

Not sure if this helps but this is the best I've found on how to calculate the focal point of an offset parabola:

_http://pagesperso-orange.fr/f8apf/hypers/antenne_parabolique.xls

I know what you're really looking for is a formula to calculate the parabola, not the focal point but I thought thus might be useful too.

 

[electrobby2009]

Yes I made a 6 foot dish (Aluminium Mesh) at home and it is working fine after 10 years till recently an extra ordinary hailstorm unevened the mesh. I used it for C-Band in Pakistan

 

[z4reg]

Hi guys ... i m also trying to make one c-band dish(prime)!

What is optimum F/d ratio ? 0.388?

 

[Payo]

Here are some photos of an experimental way to make a dish out of a large party balloon (€2 from Toys'R'us, 80cm diameter and definitely NOT spherical) and about half a can of polyurethane foam (the stuff that builders use to seal gaps in walls) that I had left over from another project (€4.50 from Carrefour my local supermarket).

The foam dish is extremely light and rigid and while it is not good enough to bother finishing with foil the process is very cheap and incredibly easy. The foam is easy to trim with a sharp knife so the back and edges can be made to look neater. It should be easy to finish with a layer of car body filler and aluminum foil so it might be worth doing some more experiments with this system. My big mistake was not to do anything to remove air pockets from the foam once I had squirted it onto the balloon.

The next time I have spare foam I'll do some more tests.

 

[Payo]

Forgot to add: That measuring rod is marked with 10cm bands