Support arms for Fortec Star Dishes

[emuman100]

Hello,

On my 2.4m Fortec Star prime focus dish, have you noticed the LNB arms are not adequate for a heavy dual output Chaparral feedhorn and two heavy Norsat 8515 LNBs? When re-aligning, I noticed that the whole scalar ring and feedhorn/LNBs seem to sag, but ever so slightly. I had to bend and twist the scalar ring position to get the focal point on the right spot as well, and find it very difficult to find the right spot when aligning. Once I got the azimuth and elevation spot on, it takes playing with the feedhorn position and LNB skew to get the strongest signal.

Is this normal with these dishes? My 1.8m Fortec Star prime focus dish had the same problem with the arms as well. Is this normal for all prime focus dishes? I'm guessing not. Should I use, say, metal wiring conduit as a good replacement? And use four of them instead of the three it comes with?

Thanks.

Jonathan

 

[cracklincrotch]

Yes, you can use metal conduit to do that. Just flatten out the ends so they mate with the dish the same way and you should be all fixed up.

 

[Anole]

alternative

I used some metal conduit to make LNB side support arms for a small Ku dish, recently.
So, the same thought came to mind.
They were a lot shorter than you'd have on a BUD, and quite stiff.
However for the span you're talking about, I don't know if the strength to weight ratio would be appropriate.
So, if you determine that a piece long enough, and large enough to be stiff, would be too heavy ...
... there's also aluminum tubing available at the Home Depot type stores.
It's anodized, comes in various diameters, and is a bit more expensive, but for three or four pieces, maybe worth the one-time cost.

Just something to think about.

Regardless of the tubing selected, there's a question of bending it.
If you don't have a proper tubing bender, could you have it done at a muffler shop?
Might be cheaper than a machine shop.
Or, the muffler shop might have other materials and suggestions.
Worth an ask. -

For the tube end where I attached to the dish, I did squeeze it flat, grind it off, drill a hole, and bend it to the appropriate angle.
If your dish has a different attachment technique, it might be best to duplicate it.

On the end where the support strut attaches to the LNB scalar (or scalar support plate), there are many ways in the many BUD pictues on the forum.
Here are two I like.
- commercial dish, in the picture gallery of McGuyver.
- bracket/tab designed by CadData, as seen in this picture by PopCornNmore.
(I've built the tab, and it's easily adjustable)

 

[phlatwound]

I have an old buttonhook-equipped dish that I was considering taking some very small cable (1/8" max), and some little turnubuckles to adjust the feed support with.

You might be able to rig something like that to adjust your existing feed suport, if it doesn't need to move much. Probably would have to reinforce the areas where you attached the cables to the edge of the dish, too much localized pull would tend to distort the parabola, I think.

 

[emuman100]

Thanks for the reply guys. I think the aluminum tubing or steel conduit might be the best solution, though the steel would be harder to bend and crush the ends. With a lightweight BSC621, the arms are perfectly adequate. I guess that's what the dish is made for, the lightweight LNBs.

I will use the steel cable and turnbuckles to hold down the dish to the ground so the wind won't blow it down like it did. The turnbuckles are a great idea to adjust the tension on the fly.

Jonathan

 

[Lone Cloud]

I used the smallest diameter aluminum tubing I could find for this purpose an another dish I have. I did it the exact way described here - flatten ends, make same length, identical bends and holes. Should work.