WS Net Primestar 84E Dual Feed

[ziggy1222]

I acquired a WS Net Dual Feed dish on ebay some time ago. I wanted to post the particulars as to how it is designed for those who like to experiment with multiple feeds on one dish.

It is a Channel Master 84E elliptical dish with two 75E feedhorns using NJR 2119F LNB's(two F connectors...one vertical & one horizontal). It is designed for 93 degree and 99 degree satellites. The LNB spacing is 2 13/16" center to center for this 6 degree span. Neither LNB is boresighted...they are both equally placed off center. The LNB focal distance is about the same as that of the 84E arm.

Those familiar with the Channel Master elliptical dishes know that the 75E feedhorn arm is about 1 1/2" shorter than that of the 84E feedhorn arm. Also the feedhorn itself on the 84E(3 3/8" tall) is larger than that of the 75E(2 5/8" tall).

I guess they figured that using the smaller feedhorn would keep this from over illuminating with the dual feed. I thought they might shorten the focal distance to keep this from happening. Most of the hobbyists here probably use a round feedhorns for multiple feeds rather than the stock elliptical feedhorn so your risk of over illuminating is reduced.

All of this just for your information...FWIW.

 

[Anole]

I had to read that three times to picture it.
Think I got it.
Could you post a few pictures so I can check against my mental one?

Who is WS Net, and why do/did they have dual feed dishes?


edit:
Oh, the shorter LNB support arm on the 75e vs the 84e is no problem.
The focal length of the dish is probably less.
But, the F/D ratio is probably equal.

And on the 84e dish, the little horns are located about the same distance as the 84e feed would be.
...because that's where the dish focuses.
Would 84e feedhorns have bumped into each other?

 

[ziggy1222]

I can't give you pictures because its not set up.

WS Net has gone bankrupt some time ago-it was an Austin, Texas based private cable operator and provider of satellite video programming to small cable operators...the vast majority which were private cable operations in multiple dwelling units. I suspect I got this as surplus equipment on ebay.

You are right the 84E feedhorns are too big-they would have bumped into each other. It probably was a physical reason for using these...I thought it would have been an electronic reason because a LNB off center would over illuminate the dish on one side wouldn't it? I figured a 75E feedhorn would illuminate a smaller footprint and maybe somewhat under illuminate the dish top to bottom and on one side...but not over illuminate on the other side.

Another way to prevent over illumination if you used and could use the 84E stock elliptical feedhorn that was offset from boresight would be to shorten the focal distance wouldn't it?

Hobbyists using round feedhorns on an elliptical dish instead of the stock elliptical shaped feedhorn would probably run little risk of over illiumnation on the one side because the footprint is round not elliptical.

One other thing I forgot to mention was this dish came with a real sweet mount that let's you skew the entire dish. If you want to see pics of that I could do that for you.

Corrections, amplifications, bricks etc. welcome !

 

[Anole]

dish talk:

You are right the 84E feedhorns are too big-they would have bumped into each other.

It was just a guess. If the birds had been a little farther apart, they might have used the bigger feedhorns.

But, this is no different from getting SatAV's little GeoSatPro Bullet LNBFs.
They are very small diameter, and some of the members have used them to great advantage for getting two very-close birds.

Another way to prevent over illumination if you used and could use the 84E stock elliptical feedhorn that was offset from boresight would be to shorten the focal distance wouldn't it?

No, the focal distance for a given dish is the focal distance.
The dish does have an F/D ratio, and you want to match the F/D of the feedhorn to the dish.
In the case of round dishes and round feedhorns, that's straightforward and obvious.
The elliptical dishes 'n feeds are really no different.

Hobbyists using round feedhorns on an elliptical dish instead of the stock elliptical shaped feedhorn would probably run little risk of over illiumnation on the one side because the footprint is round not elliptical.

The round feedhorn sees a round piece of the dish, and that's not a 100% match to the dish.
So, in theory, you don't get maximum gain.
In practice, many such collaborations produce sufficient signal for the task.
One example that comes to mind would be where a stock linear LNB and feed is on a wide elliptical DirecWay dish, with side-mounted DishNetwork LNBfs.
The DirecWay feedhorn sees the entire dish and gets great gain/side lobe suppression.
The round DBS LNBs see round portions of the dish, but since they are working with much stronger signals, the result is excellent.

One other thing I forgot to mention was this dish came with a real sweet mount that let's you skew the entire dish.

Elliptical dishes really need to be skewed for maximum performance.
... and also to line up multiple LNBs, if you are using them.