Accuracy of elevation scale on 33" dish

[kooguy]

Just wondering anyone had bad experience with elevation scale on FTA 33" dish? I had a Winegard 30" dish and the scale is very accurate once the mast is plump.

I was trying to help a friend's to aim his 33" dish and was having problem trying to locate Galaxy 3C. I used my Visionsat IV 20 PVR receiver and LNB on his dish, set the elevation to 37.5 degree but no luck getting any signals. I kept lower the elevation till 35 degree, the signal strength still at 87 but zero on quality. I try to go up to 38 degrees but the signal strength go down hill. I didn't go lower than 35 degree.

I'm pretty sure the azimuth is very close to where Galaxy 3C is..The 33" dish my friend had was made in Tawan and had letter "FT.." on the surface.

Just hard to imagine the scale on dish can be off more than 3 degrees.

Settings:

95.0W Galaxy 3c
Frequency: 11780 Mhz
LNB Power: ON
LNB Type: Universal
LNB Freq: 97500,10600
DiSEqC all OFF

 

[Anole]

Well, it could.
Also, the LNB support arm could be bent.
Sometimes people use the wrong LNB mount, making the LNB too high or low.
And, as you mentioned, the post it's mounted on could be off-plumb.

In one famous case, the manufacturer interchanged mounts between 80cm and 90cm dishes (if I remember correctly), causing an error of maybe 5°.

 

[Mr Tony]

What brand?

I've seen some old Fortec dishes be off by up to 7 degrees. Also if there is no edge like the WInegard you might have to line up the nut to the elevation. Had a "Hotdish" that was like that

 

[GrumpyGuy]

I feel your pain, Kooguy. Yesterday I was doing a site survey at a friend's place. I knew I would not be able to get a full view of the arc from any one spot on his property. With compass and protractor I found a spot where a dish would just barely see 74-125 ... maybe. It was going to be tight.

To be sure, I did a temporary setup using a no-name, untested, stamped steel dish I picked up on Freecycle. Much frustration followed.

Long story short: The elevation settings on the dish are off by roughly 7 degrees.

 

[AcWxRadar]

33" dish trying to locate Galaxy 3C.

Elevation to 37.5 degree but no luck getting any signals.

Lowered elevation to 35 degree, signal strength still at 87 but zero on quality.

Try to go up to 38 degrees but the signal strength go down.

I didn't go lower than 35 degree.

I'm pretty sure the azimuth is very close to where Galaxy 3C is..

Settings:

95.0W Galaxy 3c
Frequency: 11780 Mhz
LNB Power: ON
LNB Type: Universal
LNB Freq: 97500,10600
DiSEqC all OFF

Kooguy,

You made no mention of a motor, so I assume you are setting this dish in a fixed point manner. If this is correct, then have you set the LNB polarity correctly? The LNB should be rotated ~16 degrees CCW (when you are facing the dish).

If you are using a motor, then let us know as that is going to change some things.

Using your hometown location as coordinates (Ajax, ON) I get a dish elevation of 37 degrees and a True azimuth angle of 202.5 degrees and an LNB polarity angle of +16 degrees (this should be CCW if standing in front of the dish).

Ensure that you are using TP 11780 H with symbol rate 20.760 and FEC of 3/4 (if not auto set). This should be the CCTV channels. I think that is what you were trying for, correct?

You can also use TP 12050 H with symbol rate 20.000 and FEC of 3/4 also. This should get you MAC TV which I find pretty strong down here.

If you don't trust the elevation markings on the dish assembly, you can put a straight board across the front of the dish from top to bottom and place an inclinometer on the board to read the angle.

RADAR

 

[1ADAM12]

Kooguy,

If you don't trust the elevation markings on the dish assembly, you can put a straight board across the front of the dish from top to bottom and place an inclinometer on the board to read the angle.

RADAR

Yes that works very good, but you must know the dish offest angle (20,22,23,24) and subtract it.

On prime focus you read direct of course.

 

[AcWxRadar]

Yes that works very good, but you must know the dish offest angle (20,22,23,24) and subtract it.

On prime focus you read direct of course.

1ADAM12,

Correct. Kooguy will have to inform us of the dish brand and model so that the proper offset angle can be determined (if he doesn't know the angle of his friend's dish right off).

I am betting that it is just the LNB polarity angle that needs attention.

RADAR

 

[B.J.]

Well, it could.
Also, the LNB support arm could be bent.
Sometimes people use the wrong LNB mount, making the LNB too high or low.
And, as you mentioned, the post it's mounted on could be off-plumb.

In one famous case, the manufacturer interchanged mounts between 80cm and 90cm dishes (if I remember correctly), causing an error of maybe 5°.

What brand?

I've seen some old Fortec dishes be off by up to 7 degrees. Also if there is no edge like the WInegard you might have to line up the nut to the elevation. Had a "Hotdish" that was like that

Re the "manufacturer" that interchanged mounts, I'm not sure if it was the manufacturer or the dealer, but I think that WAS the Fortec dishes sold by Sadoun. My "guess" is that Sadoun sold the dishes with an optional U-bolt mount that was not specific to the dishes, and that caused some of the confusion. Ie the mount has to be matched to the offset angle and mounting position on that specific dish, so a generic mount won't have an accurate scale. However there also seemed to be some confusion with respect to just what was packed in the boxes. My 90 CM came with instructions for an 80CM dish.
I found that the scale on the stock pole mount on my 90CM was fairly accurate, however as Anole mentions above, the accuracy of the scale is only meaningful if the LNBF arm isn't bent. My LNBF arm was bent a little bit. I have since corrected this and additionally stabilized the arm by connecting wires to the arm that connect to a bolt up on the dish edge.
The lnbf arms on the Fortec dishes are not very sturdy. One poster at another forum had one which had gotten bent during shipping, and he was off by something like 15 degrees or more. That situation was solved by him posting pictures that made it apparent that the arm positioned the lnbf so high that it almost made the dish look like a prime focus.

 

[Anole]

Since the dish in question was NOT a Fortec dish, I didn't think it appropriate to mention the thread specifically.
However, since we've gone this far, here it is:

Sadoun discusses Fortec Star dish elevation confusion:
http://www.satelliteguys.us/free-air-fta-discussion/173704-general-fta-question.html#post1809188

Iceberg hit a point I always forget: where do you look to set the elevation?
He or others have posted pictures around here before.
Some show you set the elevation marking in line with the middle of the adjustment screw.
Some call for alignment with a tiny metal bracket on the screw.
Some you look through the adjustment slot and align the edge with the stamped numbers.
Not knowing the actual dish in question, it could well be no more than an operator error in setting the wrong elevation.

And that all said, a bent LNB arm is still my favorite.

 

[GrumpyGuy]

Kooguy, are you sure the LNBF is in fact a UNIVERSAL, and not the more common STANDARD type?

Even with 16 degrees of skew error, if everything else were correct, I would expect Kooguy to have seen at least some rise in Q - perhaps not enough Q for a reliable lock, but at least something. But yes, it is best to have everything possible working in one's favor when aiming a dish, skew included.

Also, you could try hitting your true south satellite with zero skew. Search a wide range of elevations. If you can get something there, note the difference between the elevation setting of the dish mount, and the actual elevation of the bird. Then skew the LNBF, and go back to your search for G3, using the difference as a correction factor.

 

[tvropro]

I never go by those, scales they usually are off. Better to use an inclinometer and yard stick as shown in my attached photos. Never went wrong with this method.

 

[AcWxRadar]

I never go by those, scales they usually are off. Better to use an inclinometer and yard stick as shown in my attached photos. Never went wrong with this method.

TVROPRO,

In your pix, what angle are you setting the inclinometer to? Are you setting it to the dish elevation angle that you would obtain from an angle calculator?

Is there a reason that you are not taking this reading directly off the LNB support arm? That appears to be fairly parallel to the angle you are setting with the yardstick, but I have a question about setting the yardstick on top of the LNBF and at the bottom perimeter of the dish. Is the angle you derive or set from this simply "just close enough" to get you into the ballpark? I understand the theory in what you are doing here, but I don't quite follow the accuracy. Please explain.

RADAR

 

[AcWxRadar]

There are many items to check in this case.

1] Is the LNB type correct? Standard VS Universal?

2] Is the LNB polarity (polarization angle) set properly?

3] Could the LNB support arm be bent (or not properly bent)?

4] How are you judging the elevation setting? What pointer/marker or reference point are you using to take the reading on the scale?

5] Are you absolutely certain of the azimuth position for sat 3C? You are not off a few degrees one way or the other?

6] Is the dish directly mounted to a mast or attached to a motor? If attached to a motor, there are other criteria to consider.

7] What brand and model is your friend's dish? What is the offset angle?

RADAR

 

[Conky]

Saved myself a lot of headaches using the board and printed out protractor. I was surprised how accurate it was. Just have to know your dish's offset angle

 

[kooguy]

Thanks for all the replies...Really appreciate all the help!

Brand: The dish has marking as "FTA Tech"
LNB: I took my LNB (Fortec FSKU-2VN, dual output) and mount it on the above dish.
Setting of LN: Universal, has been set correctly with my Visionsat receiver, no motor is used.
At my town, 37.5 degrees elevation is all I need for my Winegard dish.

I also try the skew like 10 degrees, didn't work either. On my Winegard dish, I don't have to set any skew angle.

I took my receiver and LNB over to my friend's house, so the only difference is the 33" disc. My receiver had the correct settings and working properly at my house.

At this point, I'm pretty sure the scale is off since the mast is level 100% (using a carpenter level) and also secure with two side support, little chance of off plumb.

I'll try again this coming weekend and let everyone know the result...

 

[AcWxRadar]

Kooguy,

The rest of the group and I have pointed out the most obvious and mundane items to check thus far. I am sure that you have the sense to check out each of these items for this installation and double check them to be certain.

I am going to place a bet, however, that your LNBF polarization angle is incorrect and that your azimuth aim is not quite on the mark.

I have little to base this assumption upon, I am just going upon my own first "gut" reaction. I hope you don't mind too much if I bet on your setup, but I want to test my first instincts.

From the information that you have presented thus far, I don't feel that I am gambling with too much. I think that you have a good handle on most everything that you are doing already, so gambling on the items that I have chosen leaves me with pretty fair odds.



I will definitely be awaiting your response regarding what you find to be the problem. There isn't a great deal that we can do from here at this point. You will have to do some testing and provide feedback from here on out so that we can analyze the situation better.

Good luck, of course.

Gordy (RADAR)

 

[kooguy]

Hi all,

The elevation scale was off by 5 degrees...With a little adjustment, I was able to get good signals for CCTV-4. I'll stick with a brand name dish like Winegard anytime.

Thanks for all the help.

 

[Mr Tony]

sweet

Glad you got it working