torodiol -t90

[cyberham]

Anybody in Hawaii? http://honolulu.craigslist.org/oah/ele/4298197497.html

 

[RimaNTSS]

Pendragon
I came to approximately same diagram of sensitivity of T90.
Would be interesting to see some pictures of your installation.
As I've said before- I am happy with this dish.

 

[toucan-man]

In terms of sensitivity, I have to disagree with others. In a post way back, I provided test results from a very careful comparison of sensitivity across a T90's arc, and then to a 1.2 m as a reference. In the center few degrees the T90 outperformed a 90 cm dish, and was very close out to about +/- 10 degrees. By +/- 20 degrees, the the gain was only comparable to a 76 cm dish's performance.

This is good info. The center of my dish (105W) does just fine (excepting in heavy rain when the lnbf's front cover is getting pelted), but from your example it seems unreasonable for me to have expected to get both 125W AND 87W on the same dish with good results. I'd love to have a T120 dish! I agree the adjustment hardware is robust, mine aligned easily once I realized I had the secondary reflector on upside down and could only get vertical signals at the wrong elevation.

 

[Balock]

I'm guessing that the T90s have little problem with DVB-S2 signals? That's my main problem with my T55...I've never successfully received an S2 signal with it. The PLL LNBFs can't overcome the lack of signal strength from that smaller reflector.

Other than that, I'm happy with it and even have a second one that I've not assembled yet. However, I'd prefer to put up a T90 if I come across one at the right price and time.

 

[pendragon]

RimaNTSS - Your sensitivity measurements are stunningly close to mine. Science and engineering are great. I don't recall if I've posted anything before, but I've attached a photo of my toroid garden, along with another with detail of the LNBs on one of the toroids. This was a few years ago, but not a lot has changed.

Balock - I have no problems with DVB-S2 signals on any of my toroid LNBs. A 90 cm-equivalent dish is a decent threshold where one starts getting most of the FTA signals that are there. My understanding was the T55 was intended for the more powerful DBS birds. One minor point - while PLL LNBs are generally far more stable frequency-wise than ordinary LNBs, it is very common for them to suffer from higher phase noise. Unfortunately successful DVB-S2 reception is dictated more by low phase noise than frequency stability because modern receivers can easily track the latter.

 

[Dee_Ann]

View attachment 94806View attachment 94807

WOA......... :

 

[Balock]

Unfortunately successful DVB-S2 reception is dictated more by low phase noise than frequency stability because modern receivers can easily track the latter.

Good to know...I hadn't considered the phase noise aspect. The only non-PLL Ku LNBF I have is a Primestar dual-output from one of my 1M dishes and I currently don't have it installed. I very much doubt it would easily fit on the T55 without a custom mount.

 

[updatelee]

The signals were receiving are modulated by phase relationships. The higher order the modulation the closer those phase points are the more phase noise effects them. Pll's will always have a higher phase noise then a quality dro. Pll's excel at freq stability at the cost of phase noise. Freq stability helps allot on extremely narrow SR, sub 1000ks/s. Which we rarely see here in NA.

UDL

 

[RimaNTSS]

pendragon! Great toroid garden you've made! Mine is much more modest. And installation is still not finished.

 

[pendragon]

RimaNTSS - that's a very professional looking setup, and a very astute use of the space you have to work with. Hope your installation is soon complete and you can enjoy the benefits!

 

[RimaNTSS]

Thanks. This is my temporary installation. Dish simply moved with me (3rd time). Local rules do not appreciate installation of antennas, so hided it inside the balcony. My problem is, that I am eager to install also Gregorian type dish next to T90.
Actually, I have some technical issue with T90- main mirror has changed it's shape. I put horizontal and vertical treads and there is about 15mm difference between treads. Therefore ATM I can not tune it to maximum arc. First I should eliminate this bent first and than finish setup. I have 2 possible reasons of bent: something happened during transportation operation. Or, which I tend to believe, mounting pole is too big in diameter, and when I stick antenna to it shape of mirror changed. I need some time to check it.

 

[polgyver]

If there is such a distance between threads, there is a distortion of dish shape. Instead of threads, I used thicker rope and shoelace, more visible in pictures.
My dish also has focusing problems, and presently is waiting for better weather to be serviced. However, string test is OK...
It is highly unlikely that your mast caused distortion - there are so many "links" between mast and the "bowl". I used 60 mm aluminum pipe, and it fits OK.
What pipe did you use? Four pictures follow. Cheers, polgyver.

 

[Cham]

On the Ku dishes I usually use the strings in an X pattern rather than the + pattern, saves removing the LNB support. Sometimes the weight of the support can distort the parabola somewhat, and on the 1.2m fortec star I use a support rope and a spring to remove some of the weight of the arm components, I ran the rope through a hole at the top of the dish and tie it to a spring attached to the top of the mount in the back. Seems to do the job. That looks like a better dish than the one I have and I like the mount on it!
-C.

 

[mikekohl]

Be VERY careful. When they were first introduced, I had two shipped to me by BAX Global Air Freight to justify and reduce the cost each for freight charges. While packaged well, they are not very strong. Temporarily setting one up on a piece of plywood, I did not have enough weight on the base to keep it stable. In a 20 MPH gust, it tipped over, only falling about 2 feet. That small drop totally clamshelled the reflector. I now use the remaining two subreflectors as an overhead weather cover above the LNBFs on 6 foot offset dishes that I have managed to install multifeed platforms with as many as 13 LNBFs. See the front page of the Global website at www.global-cm.net to see what that looks like.