Fixed skewed dish install

[Shawn95GT]

Wow, there must be some trick to this because I tried for well over an hour and got zip with my dish skewed while hunting for 43.1W.

Is there a calculator out there that calculates the dish elevation when the dish is skewed?

I had the dish pretty much standing on it's side with a skew angle of 54° or so. It didn't take me too long to figure out that the dish elevation scale wasn't particularly useful if the dish is skewed.

I finally gave up, skewed the dish back to straight up and down, skewed the LNBF and locked the sat in a couple minutes.

I'd like to give it a shot with the dish skewed again as I'm sure the dish is more efficient that way vs a skewed LNBF. The signal at 43.1W is marginal. Any way I can better that is welcomed!

Thanks,

 

[concord]

It is my understanding that if you are using the motor to move your dish, the motor will tilt the dish, therefore the LNB will be skewed. Normally you set the skew to zero at your True South location. Skewing it once on a sat may help to fine tune it a little bit. Haven't tried the sat at 43, over the atlantic yet...

Check out the fixed dish calculator at:
http://www.satelliteav.com/page/show/418

 

[Anole]

I'd like to give it a shot with the dish skewed again as I'm sure the dish is more efficient that way vs a skewed LNBF.

I agree that the dish might be more properly oriented on it's side for large angles of skew, if it's a non-round dish.
For instance, if you have an oval ChannelMaster (like some labeled as PrimeStar, StarChoice, and Globecast).
And most surely for the DirectWay.

However, I'd like to theorize that the round dishes (yea, egg-shaped offset feed) do not benefit from skewing the reflector.
You know actual center-fed dishes wouldn't.

The signal at 43.1W is marginal. Any way I can better that is welcomed!

... more metal...

But onto more practical suggestions.
If you want to practice your aiming and check the antenna elevation errors...
.rig up a small dish with a circular LNB,
..dial in your elevation and skew,
....and shoot for a DBS bird that's low on your horizon.
Should be easy to acquire, and even tune with a meter, then you can check the elevation errors.

 

[Shawn95GT]

Ok.. let me explain further .

I have the motorized 75e... and then I have my 'old' 75e which is on a starband skewable mount.

I put together a non-penatrating mount that's been sitting in my yard dang near a year now and decided to shoot for Dr Dish this weekend. Now this particular non-pen was from a small company what was rolling it's own wireless connectivity between remote sites. Because of this the mast is 10' tall (see pic). I skewed the dish to 54.5, dialed in 9 degrees elevation to start with and went to work.

This got old to play with like this but I wanted to try it up there first because I figured with my low elevation to the bird (8.7 degrees) I needed all the help I could get.

This didn't pan out though...

I took the dish off and went after my sawzall. I cut the pole roughly in half, re-skewed to zero (well 90 on the dish, but you get the point), eyeballed the LNBF to 45 degrees or so and went hunting. I set the elevation as per Satfinder and didn't get a thing.

I decided to hit somehting I knew I 'could' see and use it as a point of reference. 58w here I come. I quickly locked on 58w and compared my elevation marking to what Satfinder said. It was +4 degrees.

I dialed in 12.7ish elevation and swung the dish East. There it is!

Ok... where to go from here...

I figure I can take the body off the LNBF and get it siting down in the saddle like it should. This may correct the +4 situation. It may even better illuminate the dish. This is an eliptical dish (75E) and I think it would be beneficial to skew it. Of course I'm kind of already in a 'less than optimal' situation with a universal LNBF strapped on the Primestar saddle. I just want to optimize what I've got to work with here .

Now... Let's say I take the dish, locked on 43W and skew it 54 degrees. My effective elevation is now something in the neighborhood of 3-4 degrees and my azimuth is dorked 15-20 degrees East.

There must be a calculator for this. What really sucks is not knowing the exact Azimuth you're aiming the dish at.

See where I'm coming from?

PS - never mind the wiring around my polar mount and the motorized 75E. That was my dog's handy-work

 

[Anole]

I just want to optimize what I've got to work with here .

Damn!
You don't give a guy much to work with, tying his hands like that
Let's see:
1) non-optimal dish
2) non-optimal LNB
3) non-optimal LNB location
4) non-optimal LNB feed-horn
And we can't change any of these variables?
...hrmmm... you sure make it a challenge...

 

[Shawn95GT]

Damn!
You don't give a guy much to work with, tying his hands like that
Let's see:
1) non-optimal dish
2) non-optimal LNB
3) non-optimal LNB location
4) non-optimal LNB feed-horn
And we can't change any of these variables?
...hrmmm... you sure make it a challenge...

I'm flexible - I just don't want to buy anything .

#1 - If it can be made to work, cool. Otherwise I'll keep holding my breath for a free 1.2M from a gas-station tear down. If not that I might have to break down and buy a 90cm dish when I find a smoking deal.

#2 It's a good LNB (0.3 Univ), just not optimal for the eliptical dish.

#3 is fixable, just pop the case and strap it down.

#4 goes with #2. I have the QPF / proper feedhorn I could try on the dish from my motorized dish to see if it helps. The TP is 12.050 so the STD LNB should be fine.

I'll try the QPF / proper feedhorn next weekend. It'll be a good goal to try to match whateve rit can do as it really should be the 'best case' scenario.

Am I totally off base with my observation of a skewed dish vs a skewed LNB?

Thanks,

 

[Mr Tony]

Shawn
When I set up Hispasat on my Starchoice skewable dish, it was bang on (well really close...the elevation was 9.1 and it was maxed around 8 or so)

 

[Mr Tony]

This is an eliptical dish (75E) and I think it would be beneficial to skew it.

yes. If you can skew the dish, by all means do that. Then more signal can hit the dish

 

[Shawn95GT]

Thanks Iceberg. Maybe they 'did' put a little more thought into this dish than I gave them credit for.

Here's the gameplan:

Lock 43W like I did before
pop the case on the LNBF, re-peak and hopefully see an improvement.
skew the dish, re-peak.
If it isn't a total PITA, try the QPF / Starchoice feedhorn on for comparison's sake.

 

[Anole]

You can prove me wrong in your tests, but . . .

Theory suggests you won't get any signal change on your elliptical dish from skewing it with that improper LNB
If you put an LNB with a horn to match the elliptical dish (say the horn that came with the dish), THEN I would expect to see a better signal by skewing the dish on its mount.

I'm flexible - I just don't want to buy anything

That's why I found your restrictions above so frustrating.