Anyone tried to make BIG dish at home?

[ynotdu]

when Sky was Analouge at 19.2 east I used a Dustbin lid as dish
Not at all helpful I know but felt the need to boast about it! lol

 

[Satcom1]

Yes, you are very likely correct about the analog signal being easier to capture. Certainly it is better quality.

 

[vjkumar]

Hello

can any one guide me to get calculations for arriving the offset dish of size 10 and 12 ft.

vkumar

 

[T_G]

This dish produces signal strengths of 98% on Coolsat 6000 Premium receiver. Sorry to say that that does not produce a usable KU or C-band signal, either linear or circular.

It would make a dandy solar cooker with mirrored surface.

I will try to come up with a new parabolic dish that is simple to make and works really good for little cost and effort.

It is valuable to know one more thing not to try. <--

Thanks for your interest in my project.

Still: Well done, I applaud you for trying and testing and coming to a conclusion. I certainly enjoy reading this thread. Next dish will be better!! :-handclap

 

[BombedOne]

I talked with one local importer today, as he said, shortly he'll have stock of 2.4m and 3.6m C band mesh dishes for reasonable price. Interesting, if anyone had tried to receive Ku band signals using C band mesh dish.

 

[Satcom1]

I talked with one local importer today, as he said, shortly he'll have stock of 2.4m and 3.6m C band mesh dishes for reasonable price. Interesting, if anyone had tried to receive Ku band signals using C band mesh dish.

Hi BombedOne-

Many in USA use later model mesh dishes for both KU and C band. Earlier model mesh dishes had very wide mesh and KU was not useable. Now with smaller mesh made for KU it works.

The LNBF in my avatar is dual C/KU and is used on some prime focus mesh dishes here. Some people side mount KU LNBF to normal C LNBF. This requires a slight offset of dish for KU reception.

They tell me that KU on a big dish 2 meters or more is difficult to set up and many use one meter dish just for KU.

Good Luck, I hope this info. helps. you.

 

[BombedOne]

hehe yes I know - bigger the dish - sharper is the focus. We have 2 meter solid aluminun prime focus dish at work, just turning one of adjustment bolts for several degrees only, strongly affects signal.

 

[casser]

I talked with one local importer today, as he said, shortly he'll have stock of 2.4m and 3.6m C band mesh dishes for reasonable price. Interesting, if anyone had tried to receive Ku band signals using C band mesh dish.

If the mesh have smaller holes than 1/10 Wavelenght of the higher frequency, you will have no problem.

299.8/12750=0.0235 meter

0.0235/10=0.00235 meter <=> 2.35mm

To receive 12750mhz, the mesh holes will have a maximum diameter of 2.35mm.

This dish produces signal strengths of 98% on Coolsat 6000 Premium receiver. Sorry to say that that does not produce a usable KU or C-band signal, either linear or circular.

98%, what dish do you think it equal´s? 30cm/45cm/60cm/etc?

 

[BombedOne]

Today I went to visit that shop again. I liked the dish, I can't hardly say it's a mesh, it's more punctured aluminum, than mesh, holes are not greater than 2mm. But price was the thing I disliked the most - about $400 for dish with ground stand and positioner together. And as he said, he can't sell dish alone, since stand and positioner are made exactly for this dish, and he will not be able to sell them separately.

 

[Satcom1]

Casser-

On my 1 meter Primestar I get a 93% max signal on the strongest transponder. 98% on this 48" diameter, several sats. Iwould guess it is capturing like a 1.8 meter dish.

I don't have an analog reveiver to demodulate the signal. We still have a few NTSC channels (analog).:mad:

In Googling parabola, I came across a guy that used a rubber sheet over a 55 gallon drum and filled it with plaster of paris to make a parabola mold. Does anyone here know if this works? Does it make a true parabola?

 

[casser]

@Satcom1

A 48" dishoven performing like a 1.8m dish is great result´s..

But i dont understand why you say this: "This dish produces signal strengths of 98% on Coolsat 6000 Premium receiver. Sorry to say that that does not produce a usable KU or C-band signal, either linear or circular."

Why is not usable?

 

[Topper]

@Satcom1

A 48" dishoven performing like a 1.8m dish is great result´s..

But i dont understand why you say this: "This dish produces signal strengths of 98% on Coolsat 6000 Premium receiver. Sorry to say that that does not produce a usable KU or C-band signal, either linear or circular."

Why is not usable?

Signal strength is not so important with digital, it is more signal quality that counts. Anything below 15-20% and you would be hard pressed to receive a picture

 

[Satcom1]

@Satcom1

A 48" dishoven performing like a 1.8m dish is great result´s..

But i dont understand why you say this: "This dish produces signal strengths of 98% on Coolsat 6000 Premium receiver. Sorry to say that that does not produce a usable KU or C-band signal, either linear or circular."

Why is not usable?

Casser-

I need to modify that statement, the term (linear) can be misconstrued. I should have said produce a useable (digital) signal of either circular or linear polarisation.

The receiver seems to be telling me that it is receiving a very strong signal from certain satellites but cannot recover a MPEG TS.

It is 10 degrees here today but even with the gray paint the dish face is above body temperature. Nice and warm to the touch. Maybe it's all that Microwave energy.

One other thing, when I assembled the dish, I should have placed the second and third rings behind each other. This would have yielded a better F/D.

Divbi, is right on the mark with his insistance of 1 mm dish face accuracy. I suspect that the BER (bit error rate) goes nuts on my dish, which is actually, four cones phased some fraction of a wavelength from each other. In an analog signal that may not make much difference. In a digital signal, it maybe creating close to 100% collision at the LNBF.

While googling Parabola I found some folks making sheet metal dishes by cutting slits in the sheet like flower pedals. Maybe, I'll try that, It sounds easy.

 

[casser]

It´s strange the antenna is not producing enough quality, i cant find a explanation for that, neither experienced. Any explanations why is happening?

 

[vjkumar]

If the mesh have smaller holes than 1/10 Wavelenght of the higher frequency, you will have no problem.

299.8/12750=0.0235 meter

0.0235/10=0.00235 meter <=> 2.35mm

To receive 12750mhz, the mesh holes will have a maximum diameter of 2.35mm.



98%, what dish do you think it equal´s? 30cm/45cm/60cm/etc?

Hello

Nice information on mesh for ku band .Could you guide /post me the details on how to arrive mesh size hole for ku receiption,since I am trying to convert one of my C band mesh antena to ku band.(prime focus)

regards
Vjkumar

 

[Satcom1]

It´s strange the antenna is not producing enough quality, i cant find a explanation for that, neither experienced. Any explanations why is happening?

casser-

You may want to read up on two digital transmission formats. CDMA is superior to TDMA in wireless applications. CDMA can receive a direct signal and a signal that has reflected off a surface and is received slightly later. CDMA has Forward Error Correction software to prevent Scramble of signal. TDMA does not work so well with second signal.

This is a very simplistic explanation of these two technologies.

You may want to read about Forward Error Correction in the DVB signal.

I hope this is helpful.

 

[casser]

I never worked with Fresnel antennas, but i still find very strange..someday i will buid one and test it;)


About the 1mm accuracy, i dont have any theoricall explanation (this is only a hobby), but what i learn in the last couple of years:

-Conical Horn´s. 1mm wont make any difference, 10mm will increase/lower the gain of the antenna, maybe 0.3dBi?! yes, s-dB/VSWR/sidelobes will change, but again it doesnt change enough fto have very poor performance.


-Reflector antennas, my latest reflector antenna was a 32cm version (65% efficiency) made of aluminum cardboard (material for 1mm accuracy?), aimed to a 54dBW satellite i started with 70% signal (usually my receiver receives signal without freezes at 45/50%)..i spent the last days "molding" the antenna to perform better, the result´s..an extra 6%. If i touch or deform a little the antenna it wont affect that much.

I dont have a 30cm commercial antenna to do a comparisation, but the difference of signal between my 32cm version and a commercial one wont be very large (maybe 10%?)...for 60Ghz antennas, the 1mm accuracy will be needed, but in 12Ghz? I only need 1mm accuracy with microstrip/patch antennas (2.4Ghz).

 

[Satcom1]

I never worked with Fresnel antennas, but i still find very strange..someday i will buid one and test it;)


About the 1mm accuracy, i dont have any theoricall explanation (this is only a hobby), but what i learn in the last couple of years:

-Conical Horn´s. 1mm wont make any difference, 10mm will increase/lower the gain of the antenna, maybe 0.3dBi?! yes, s-dB/VSWR/sidelobes will change, but again it doesnt change enough fto have very poor performance.


-Reflector antennas, my latest reflector antenna was a 32cm version (65% efficiency) made of aluminum cardboard (material for 1mm accuracy?), aimed to a 54dBW satellite i started with 70% signal (usually my receiver receives signal without freezes at 45/50%)..i spent the last days "molding" the antenna to perform better, the result´s..an extra 6%. If i touch or deform a little the antenna it wont affect that much.

I dont have a 30cm commercial antenna to do a comparisation, but the difference of signal between my 32cm version and a commercial one wont be very large (maybe 10%?)...for 60Ghz antennas, the 1mm accuracy will be needed, but in 12Ghz? I only need 1mm accuracy with microstrip/patch antennas (2.4Ghz).

casser-

Have you thought about a C Band Cone antenna?

I tried to use HDL_ANT V 3 to calculate a 1.8 meter cone antenna but the formula fails to give me a length.

Do you have any suggestions?

Here AT&T had a nationwide network of folded 4-6 Ghz microwave terrestrial antennas. They looked about 4 meters high and a rhombic opening of 2 meters by 1 meter.

I'm intrigued by your use of KU cones.

I have a new layout pattern for a flat sheet parabola dish and when I get around to it I'll replace the Fresnel antenna with it. This time I'll spray paint it with the Zinc based paint.

PS: If you make a Fresnel antenna, please be sure to place the smaller cones behind the bigger cones. That was my mstake.

 

[ynotdu]

dont forget It is not only Size that counts,The L N B/L N B C(low noise block converter,makes a hell of a diffrience,the lower the better,good luck&regards

 

[slugworth]

It is interesting that old Channel Master 1 meter dishes (offset round) have been proven to perform as well as many 1.2 meter steel dishes and some 1.8 meter dishes. This dish is only available here to commercial accounts for POS terminals, what a shame. These Channel Master dishes are molded fiberglass and little is known as to why they perform so well.

Primestar retailer dishes were channel master 1.0 meter
Mine came off a radio shack roof (for free)
Many old radio shack stores that sold primestar in the early 90's still
have them on their roofs.
The back says part # 3040642-02
mold # 1.0M -02
If that is the good one you are referring to.