T-90 LNBs for linear as well as circular?

[yuccabrevifolia]

Hi folks!

Quick question. The weather here in Socal is going to improve next week so I thought I would tackle the next project.

Week before last I picked up a sealed T-90 Wavefrontier off Craigslist. $100. Along with it I got two boxes of parts. Some Wavefrontier and DirectTV LNBs and a couple of Terk switches along with a heavy duty ground mount of some kind. The fellow I bought it from spoke almost no English. Based on what conversation we did have, I had the impression he found the whole lot next to a dumpster somewhere.

I've spent probably three hours looking at posts here and a couple of other sites. I am completely confused. I know these dishes use a special reverse polarity LNB for circular signals. That will work well for Ion and Nasa. But what about linear? Do I need special LNBs to do this? If not, is there anything I need to know about the focal points given how different this dish is? I have learned from the posts here that setting this dish up can be tricky, so I want to make sure I have as many of my ducks in line as possible prior to setting this up. Forgive me if this is answered somewhere fairly obvious. Since so many here have already set these up I thought it made sense to just ask.

Also, does anyone have a recommendation on mounting? I was thinking of sinking a piece of 2 3/8 conduit into concrete to mount it on and filling that with concrete. The ground doesn't freeze up here and is mostly decomposed granite, and so I figured a hole about 3' deep by 18" diameter would be adequate for a height of 4' to the mount on the dish. I could install guy wires to rebar around the post I suppose if needed. I can't go much deeper, as I hit rock. It does get windy here. We have the biggest wind farm in the US about ten miles away.

Thanks in advance!!! I'm looking forward to integrating the majority of the FTA that I watch with the OTA we get so the kids can just flip through the channels without asking for my help (they don't do delays well ).

 

[Lak7]

But what about linear? Do I need special LNBs to do this?

Nope.

 

[yuccabrevifolia]

Thanks Lak7. Can't imagine a more clear cut answer! ;-)

 

[updatelee]

hold a clock in the mirror, notice how it looks backwards, clockwise is now counter clockwise.
hold a pencil vertical, still vertical in the mirror, same with horizontal.

because of the double reflector on a T90 you need modified lnb's to use circular lnb's with commercial irds like bev/dish/directtv. This is because those ird's expect a freq to be R or L polarized, if your using a fta ird then you wont need special lnb's either, just your R and L will always be backwards no biggie.

linear freq are not effected by the double reflector so no special lnb's are required.

 

[Mr Tony]

If you look at the pics in the review I did
http://www.satelliteguys.us/fta-mpe...ve-frontier-toroidal-t-90-satellite-dish.html

it shows the different LNB"s I used. Most were Sadoun dual LNB's...his stock standard LNB

Worked really well

And congrats on the find. Those dishes are pretty cool to use

 

[yuccabrevifolia]

Thanks Iceberg. It looks like you have at least four different models of LNB. Great. I can use what I have then. How has it worked out for you in the long run?

Yeah this was a find. It was posted as an "antenna" on craigslist, which is why he didn't sell it earlier I suppose. Over about three weeks the price fell from $225 to $100. That was the point where it became worth the 200 mile drive to pick up.

 

[Mr Tony]

Thanks Iceberg. It looks like you have at least four different models of LNB. Great. I can use what I have then. How has it worked out for you in the long run?

It worked really well for me. I dont have it up right now as the C-Band dish is on that table and I motorized a 2nd unit.

But at one time when I had a bunch of FTA receivers set up it worked really well. Here are some more pics

http://www.satelliteguys.us/free-ai...ot-t90-dish-back-up-now-2-degree-spacing.html

 

[yuccabrevifolia]

hold a clock in the mirror, notice how it looks backwards, clockwise is now counter clockwise.
hold a pencil vertical, still vertical in the mirror, same with horizontal.

because of the double reflector on a T90 you need modified lnb's to use circular lnb's with commercial irds like bev/dish/directtv. This is because those ird's expect a freq to be R or L polarized, if your using a fta ird then you wont need special lnb's either, just your R and L will always be backwards no biggie.

linear freq are not effected by the double reflector so no special lnb's are required.

That is a great example, thanks! Makes the difference easy to grasp. That should be in the original documentation for this thing.

Based on Iceberg's pictures I'm going to need a lot more coax and connectors.

 

[Anole]

no answers, just some questions:

Congratulations on the great find.!. - :up

There are a number of good discussions on the forum when members set up their dishes.
Certainly Iceberg's top the list.

One of the problems is getting satellites that are only 2° apart.
To achieve that goal, you'll see all sorts of tricks to cut down the LNB feedhorns, or use tall/narrow elliptical feedhorns.
One product that may not have been on the market at the time, is the tiny LNBF from SatelliteAV.
They now offer both single output and dual output GeoSatPro Bullet models.
Linuxman used the dual output models on a 6' offset dish to get a lot of satellites.
You might want to try a couple and see how well they fit and how the spacing works out on your dish.
That's not a recommendation, that's a question, as I don't recall anyone doing it on a T-90 (or I have poor memory) -

The other thing to look for is some web site which gives special setup and alignment info for that dish.
You'll probably find it in any decent setup thread for the T-90.
NOT using that info would be very unwise, from what I've read.
It's far more helpful than any regular dish-aiming site, when it comes to getting the Wavefrontier up! -

 

[Shoes]

Hi Yucca, I have a T-90 with the orig manual and setup instructions if you need them let me know.
Shoes