A 3.7m Prodeline dish for Astra 2D

[pjgregory]

In previous post

http://www.satellites.co.uk/satelli...0155-astra-2d-central-italy-smaller-dish.html

I described how I managed to get daytime reception of Astra 2D in central Italy with a 1.2m CM dish. Well my new Prodeline 3.7m arrived from the USA a few weeks ago, so this is the ongoing story of getting it assembled and working. Hopefully it will have a happy ending - BBC1 24/7!

The first thing you realise is just how big and heavy this thing is. The shipping crate (a cardboard box on a wooden pallet) measures 2m x 1.9m x 0.6m and weighs 256Kg. The Prodeline assembly instructions tell you to first assemble the glass fibre dish and rear metal supports, and then lift it onto the mast. They do say "at least three persons are required for the installation.... ", but still no way! So I decided to change the processes as follows.

1. I marked out the positions of the 8 glass fibre petals on the garage floor. Then, on the circmference, I used packing pieces of plywood to ensure that the outer joint was level with the center point (002.jpg). This an interesting exercise as I found that the height difference around the rim was up to 4cm relative to the center. Never assume a floor is level, not over this size anyway.

2. Using the recomended 24" centre brace and metal cover plate to support the center, I then assembled the fibre glass sections with bolts just finger tight. (006.jpg)

3. Leaving out one of the sections, I attached the metal supporting brackets and angles to the central column, again will all nuts finger tight. (008.jpg)

4. Then with the last section in place, and a ladder balanced on the center support, I tightened all the bolts in the order specified to bring the dish into shape. (015.jpg) All of the bolts holding the metal arms and support brackets were tightened really hard to ensure that they would remain locked in position for the next step.

5. Finally, I numbered and marked each joint with a felt tip pen - drawing around the metal support brackets. I then removed the 2 bolts to each joint holding the metal arms to the dish and, with the aid of my wife and willing helper, removed the whole metal support structure in one piece. Although still heavy, we could now carry this down to the dish site and mount it on the mast.

 

[pjgregory]

The Prodeline dish AzEl mount has a screw support for elevation adjustment. For azimuth adjustment, you are supposed to swing the dish by hand. Knowing how critical pointing is for a dish of this size (0.5 degree beam width), I decided to impove my chances of accurate positioning by improving the mast bearing.

Instead of the top plate of the canister bearing directly on the top of the steel tube mast, I inserted a bearing made of a disk of 8mm ptfe rotating on a disk of laminate covered MDF. (012.jpg) The ptfe disk was fixed with silicon sealer to the underside of the canister, while the 25mm MDF plate was mounted on the top of the mast (016.jpg). This gives a much bigger bearing surface then the 4mm rim of the mast pipe.

Prodeline specify that you should use a 167mm diameter mast pipe, extending some 1.8m above the ground. Since I only want to receive Astra 2 at an elevation of 37 degrees, I can use a much shorter pipe. In fact, I used the existing 100mm pipe already installed for my old 2.4m dish, with three steel angle braces bolted down to the concrete pad.

With the mast in place, we then installed the dish support assembly. (017.jpg). Working with the assembly in the horizontal position, we unbolted each fibre pannel in turn from the dish in the garage, carried it down the hill, and then re-mounted it on the support assembly (019.jpg)

With all the pannels back in place, all the bolts were tighted up to bring the dish back into alignment. Here you see the assembled dish and the next problem. Its rather visible!

So now comes the camouflage. With the dish in its correct elevation and the lower pannel removed, I could spray paint (acrylic - matt) the camouflage pattern. For those interested - see

_http://industryfigure.com/berkeley/camo.htm

The next part will look at the LMB mount as I already know that the feed horn supplied with the Prodeline is not that good.

 

[gio2010]

Hi PJGregory,

Could you please tell me where you bought your prodeline 3.7m dish?
Thank you very much.

 

[pjgregory]

Hi gio210

I bought my dish from Vincor Ltd in USA. Here is the web page

_http://catalog.vincor.com/SearchResults.asp?Cat=175

It was shipped by sea from the US to the port of Milan. I arranged customs clearance and delivery to my house directly.

PJG

 

[gio2010]

Thanks very much PJGregory

I saw their site a few weeks ago and I asked them a quotation: I asked the dish to be delivered to Perugia.
But I didn't receive any reply.
Then I sent an e-mail. No reply.

I don't understand why. How did you contact them?

And what feed support did you buy?
Thanks for your help.

gio2010

 

[pjgregory]

That is strange. I had no problem.

I ordered the dish and feed assembly on the web site and the sale just worked. A lady in the sales department - Kelly A. Riney - contacted me to arrange an export licence and shipping. Her number is tel: 001 708 534 0008.

I ordered the feed option 0800-3734 = Ku SP with cover. However this is NOT correct as the kit contains a circular to rectangular converter piece.

Coviello has posted a modification to the Prodeline feed horn here

http://www.satellites.co.uk/satelli...eral/118791-msg-rd-100-3-7-prodelin-dish.html

I am currently corresponding with him to work out how I need to modify my feed assembly. I will post my results in the next few days.

PJG

 

[trigger]

Hi Pjgregory

What a great post.
This sort of post can be so helpful to others.

Nice one - keep us informed

Thanks

Triggs

 

[Channel Hopper]

With the mast in place, we then installed the dish support assembly. (017.jpg). Working with the assembly in the horizontal position, we unbolted each fibre pannel in turn from the dish in the garage, carried it down the hill, and then re-mounted it on the support assembly (019.jpg)

With all the pannels back in place, all the bolts were tighted up to bring the dish back into alignment. Here you see the assembled dish and the next problem. Its rather visible!

The dish will not be back in alignment as the support arms have a tolerance to allow for panel deformities and manufacturing defects. You will need to loosen each of the panels, string each of the eight pieces and use a boresight tool to get the panels in place.

 

[pjgregory]

The dish will not be back in alignment as the support arms have a tolerance to allow for panel deformities and manufacturing defects. You will need to loosen each of the panels, string each of the eight pieces and use a boresight tool to get the panels in place.

Hi Channel Hopper

As I mentioned, I did lock all the metal arms togther as tight as I could and only removed the bolts to the fibre pannels. However, transfering the weight onto the arms when the dish is reassembled rather than the other way round in the garage, could cause the arms to bend a little, moving things out of alignment.

With the lower petal removed, I can get 3 strings to cross in the center within a 5mm band. I know that I can improved this when the remaining petal is replaced, but then I cannot see the crossing point of the strings. I plan to make a scafolding support on Monday so that I can stand inside the dish. Then I can do the string test correctly.

What do you mean by a "boresight" tool? I know that I have to get the axis of the feed horn aligned with the center of the dish. I have ordered a green laser pointer to go inside the tube of the feed horn so I can align the spot with the center. Is this what you mean or is there an alternative method.

PJG

 

[iceman]

The dish will not be back in alignment as the support arms have a tolerance to allow for panel deformities and manufacturing defects. You will need to loosen each of the panels, string each of the eight pieces and use a boresight tool to get the panels in place.

I agree with Channel Hopper on his above point..
One other point i would suggest is to fit the panels on to the metal frame while the frame is in totally horizontal position (017.jpg)This will make sure a ballanced weight distribution on the metal frame.
Stringing the dish with missing pannels does not mean anything cos the dish will definately change shape when the missing panel is bolted.Make sure all panels are in place and the dish is in horizontal position (017.jpg) when stringing...adjustments can be made by loosening necessary panels and correcting them while observing the strings..
And last thing is...once you get the strings right,make sure you tighten every single bolt before you tilt the dish up into position for aligning.

 

[pipino]

i´m sure Roman Dávid has an extreme experience with the dish you have ,he´s been doing some great experiments with c/ku receptions, i would ask him for advice if any doute..cheers

_http://web.dxsatcs.66.sk/php66/index.php?str=7&spr=26

 

[pjgregory]

I agree with Channel Hopper on his above point..
One other point i would suggest is to fit the panels on to the metal frame while the frame is in totally horizontal position (017.jpg)This will make sure a ballanced weight distribution on the metal frame.
Stringing the dish with missing pannels does not mean anything cos the dish will definately change shape when the missing panel is bolted.Make sure all panels are in place and the dish is in horizontal position (017.jpg) when stringing...adjustments can be made by loosening necessary panels and correcting them while observing the strings..
And last thing is...once you get the strings right,make sure you tighten every single bolt before you tilt the dish up into position for aligning.

Hi Iceman

I did put all the pannels back together with the dish in the horizontal position. I then tried putting strings across with the dish horizonal. The problem I found was that I could not get my eyes close enougth to the center to see the cross over point, certainly not with the nylon fishing line that I was using. That is why I tried again with the dish tilted.

Tomorrow, I will bring the dish back to the horizontal, put the pannel back in place and try the horizontal strings again. I have since found some 1.3mm yellow nylon strimmer cable which at least I can see. However, with four lines touching in the middle, the height difference would be about 5mm. It this too much? What sort of accuracy should I be looking for?

PJG

 

[iceman]

Hi Iceman

I did put all the pannels back together with the dish in the horizontal position. I then tried putting strings across with the dish horizonal. The problem I found was that I could not get my eyes close enougth to the center to see the cross over point, certainly not with the nylon fishing line that I was using. That is why I tried again with the dish tilted.

Tomorrow, I will bring the dish back to the horizontal, put the pannel back in place and try the horizontal strings again. I have since found some 1.3mm yellow nylon strimmer cable which at least I can see. However, with four lines touching in the middle, the height difference would be about 5mm. It this too much? What sort of accuracy should I be looking for?

PJG

Even if all four strings touched eachother you will need to pull/push them up/down to be sure they are not applying pressure to others..or alternatively use only two lines by moving them around the dish.

 

[pjgregory]

Even if all four strings touched eachother you will need to pull/push them up/down to be sure they are not applying pressure to others..or alternatively use only two lines by moving them around the dish.

Taking Iceman's advice. I moved the dish back into the horizontal position, replaced the lower petal and then tightened up all the bolts. I have now managed to find some 0.8mm flourescent orange and yellow nylon line to use for the string test.

I put the first line between two opposite panels. The second line goes between the two pannels at right angles. I tried it both above and below the first line. They touched in both positions. Then I tried the third line above, below and between the first two lines, finding the position where moving it up or down slightly just moved its neighbour as well. Finally I did the same same with the fourth line.

As far as I can see both by eye and in the photgraphs, all lines touch giving an error band in the region of 3-4mm.

So Iceman - is this good enougth?

The Prodeline manual suggests it should be better than 6mm. I am inclined to tighten every thing up and make any final adjustmnet when the dish is back to the operating position. Then I can use much finer line and get my eyeball up close to the crossing point.

PJG

 

[iceman]

PJG
Well done....your dish should be in a good shape now.
I would have used a finer fishing line myself for more precission but hey...you have done a very good job.:-righton

 

[iceman]

PJG
What's your plan for the feed assembly?Are you planning to use the feed that came with the dish?Or do some machining to fit something else?
Post some jpgs of what you have and what you are planning to do..

 

[pjgregory]

PJG
What's your plan for the feed assembly?Are you planning to use the feed that came with the dish?Or do some machining to fit something else?
Post some jpgs of what you have and what you are planning to do..

My plan is to modify the feed horn that came with the dish (Prodeline part number 0183-579) to use it only as an adaptor to the 4 struts attaching it to the dish. I want to bore out the center to the same diameter as the tube for the Invcom adjustable feed horn. I found a local jobbing engineering firm with a lathe that can do the work, but tomorrow is a festa (holiday) in our local town so they cannot do the work until Wednesday. ( This being Italy, a promise of Wednesday could really mean anytime in the future). I will post pictures as soon as I have it back.

PJG

 

[iceman]

Is this the feed you are planning to use?
What is the marked lenght in mm?

 

[pjgregory]

Is this the feed you are planning to use?
What is the marked lenght in mm?

Yes.

I am sorry I cannot measure the length as the part is with the engineering shop. I do not think in matters however as I plan to remove all of the waveguide tube leaving just a mount fo the Invacom feed horn.

Just when I needed it, my scanner has stopped working. I hope you can see sufficient detail in the photo of the sketch to see what I am planning. The scaler ring will screw back onto the tube and C-mount flange which passes through the bored out mount. The invacome tube is held in place with two set screws though the mount.

PJG

 

[iceman]

I understand what you are planning to do BUT my concern is that invacom feed neck will not have enough play to move forward/backward in your machined Prodeline part when fine tuning the focal point...

attached is the feed/LNB assembly on my 3.0m Channel Master...
notice the nuts i used as spacers to give me the necessary play i needed to get the correct focal point?
I machined the assembly myself using a square plate made of 4mm steel then attached the black plastic clamp on to it which allows for the feed to move forwards/backwards.