Replacing the feed horn

[lme]

I'm replacing the c/ku Chaparral corotor II feed horn with a new genuine one. Noticed that the scalar ring in wider/thicker then the 8 years old one from TEK2000 store, witch I believe was a used one to begin with (see screw marks):
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My question is if there is any procedure &/or tools, to install the new scalar ring parallel and centered to the face of the dish.
I'm thinking about a laser pointer (beam) !!
Forgot to mention that last month we had 2 tornados in the area; 1 small branch slightly bent 2 holding arms and knocked
off the feed horn assembly: cone cover on the ground, so I assume that the hole assembly is out of the alignment. The signal is a bit less then before. I also had to replace the servo.
Any input is welcome.Thx.

[ArloG]

For the scalar. 3 or 4 tape measures around the dish rim and a lot of patience. Or perhaps some el-cheapo fiberglass driveway marker poles from tractor supply with sharpie or printed paper markings taped to them. And patience.
To get the feed pointing straight at the dish center. I used paint can tops that fit the feed tube. Punch a hole through the center dimples. Tape a few together. Measure and cut a 'glass pole or wooden dowel. Stick it through the holes. You'll be very close. Try to get max signal aiming the dish and then tune the lnbf in.

Edit:
Thanks guys. That was a pretty sucky description. A few rulers around the dish rim that extend to a reference point on the scalar. Perhaps big binder clips or gorilla tape to hold them in reference to the rim.. I like EB's method of long bolts and nuts on the dish face to give fine adjustments. On my button hook feed, my adjustment bolts are on the scalar.
There's my spray paint can top jig I just dug out of the pile. I don't think it would fit inside of the Chaparral feed tube w/o interfering with the....."butterfly???....just inside it. But you're a smart guy. You'll figure it out.
Brain fart. Why not find a flat disc of metal that would sit in the scalar center with a center hole drilled and use the can tops? Or since it 'tis the season. A couple of nut cans taped together with center holes and a dowel. The open end of the first one sitting inside of a scalar rib.

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[lme]

Thx.
Where can I read "I like EB's method of long bolts and nuts on the dish" ?

[ArloG]

I forget. It was recent. Not that hard to figure out. But. Do your feed mount poles extend from the dish face or rim?
Look at my photo. My buttonhook feed is modded to allow scalar adjustment. It was a pic from when I first put it all together before alignment.
The adjustment bolts and lock nuts would be duplicated on the dish face if that's where your poles are bolted.17861

[lme]

The poles (4pcs), are bolted on the dish face.
I think I found a way to check if the scalar ring is centered: a magnetic inclinometer with laser line on each end snapped
on a big washer with same diameter as the feedhorn hole in the scalar. Holding this assembly with 1 hand and bending the scalar with the other hand. I already have 4 lines on the center plate of the dish: 1 set for polar axis and 1 set for the lower west sat (139w) as a service position. Each set are 2 perpendicular lines converging in the center of the center plate. As far as can remember when I got this 10' used dish, the name was StarTrak ?!?. Can't find any info on the web, but found ass'y instructions for a Perfect 10 dish, and the mesurrements look similar to my mesurrements.
Mesurrements on 4 points from the rim to the outer ring of the scalar are equal.
Tomorrow will try to install the new corotor II. Found an idea of an empiric tool to check if the feedhorn is centered:
an oil filter cap (#5) will fit over the horn, and I enlarged the hole for the wrench in the cap to fit a pet laser pointer.
Will check it tomorrow and confirm if the scalar is centered. Hope to have tomorrow another day of the indian summer !!

[el bandido]

The scalar ring helps hold the parabola of a mesh satellite dish.To see this, string the dish without the scalar ring installed, then install the scalar and string it again. Most likely, the strings will show a different dish shape with the scalar installed as compared to the scalar not installed.

Almost all of the scalar rings that are shipped with a c band lnbf are of poor quality and design. More weight in metal = more production costs. LNBF's are for the most part, cheap items when compared to lnbs. A lnbf is usually made using the cheapest parts and cheapest methods available. There are of course a few exceptions.

Here are two pictures of scalar rings for c band, The smaller one was shipped with a lnbf.
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Here are two pictures that show the difference in depth. Look at the depth markings on the lnbf:
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There is a noticeable weight difference between these two scalar rings. The scalar ring helps to hold the correct dish shape on most mesh satellite dishes. The better the scalar ring is mounted, the better the dish performance.

[el bandido]

The scalar needs to be mounted dead-center of the dish if possible. This can be hard to do when the dish is off the ground and aimed at a satellite.

Washers can be installed at the top to lower the scalar. Washers can be installed at the bottom to raise the scalar, depending on how the feed arms are mounted. Any washers that are installed to raise or lower the scalar ring should be a temporary fix because they will reduce stability. Find out where things are supposed to be, then make or get someone to make the proper mounting arms for the dish. We cannot get dish parts anymore, so we have to make them!

here is a scalar ring mounted to feed arms that have slots in them. These slots allow the scalar to slide so it can be centered. The arms should be an equal distance in degrees around the dish. The arms are not an equal distance on this dish.
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String the dish at several angles to see if the shape has changed after installing a scalar ring.

[lme]

By mistake (or not !), the seller sent me a corotor 2 plus wideband.
Can this be used for north american satellites ?
He's insisting that should be no problems....

[el bandido]

The corotor 2 plus wideband will work, but it will not be as sensitive because it is designed to work over a longer frequency range.

[lme]

The corotor 2 plus wideband will work, but it will not be as sensitive because it is designed to work over a longer frequency range.

So it is not recommended to be used in this place...

[el bandido]

It will work, but it will probably not perform quite as well as a non-wideband model. There used to be c band transponders with tv channels below 3600 MHz that most of us could get. The wideband model covers all the way down to 3400 MHz. To do this, the antenna probe is made slightly longer to cover the lower band. In general, the wider band antenna (3400 MHz) is not as efficient as the shorter band antenna (3700 MHz). So you can expect to lose a small amount of signal with the wideband model.

[lme]

It is listed as 3.7-4.2ghz circular & linear polarity !

[el bandido]

See Attached .pdf file.


The Corotor II Plus receives linear C-Band signals in the 3.7-
4.2GHz range and linear Ku-Band signals in the 11.7-
12.7GHz range. The Corotor II Plus Wideband is for
receptions of circular and linear C-Band signals in the 3.4-
4.2GHz range and linear Ku-Band signals in the 10.95-
12.75GHz range. The Corotor II Plus Wideband features a
new low loss dielectric plate. The new dielectric plate provides
a lower noise temperature and improved cross polarization.

[lme]

Regarding the corotor 2 servo motor: is any way that a servo can be repaired ?
Next question is if a servo may be readjusted ?
I found an old servo but is rotating on the opposite direction and if installed on the feed horn will move the probe to the stop position.

[ArloG]

The first place to look would be the servo position feedback potentiometer. Give it a spritz of Deoxit or regular contact cleaner and work it from stop to stop gently. If you have and can use a multimeter, perform a resistance sweep and check for dead spots. Check post #21 in the link below.
First video is what you should see without the reduction gears in place.
Turning the gear meshing the pot will turn on the motor as it tries to drive the gear train (but it can't). When you stop turning the gear, the motor circuit is satisfied and turns it off.
The 2nd video is with all gears in place and turning the skew fine adjustment from an old Drake receiver.
If there's a dirty or dead spot in the pot. Hey! Imma' poet!......The feedback circuit won't know where the actual position should be and either "hunt" or drive to an extreme and the motor will stall.

[Only registered and activated users can see links]

[el bandido]

[Only registered and activated users can see links]

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[lme]

[Only registered and activated users can see links]

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I've seen it, but is a china made bad copy of chaparral. I do have same DYNA !?!?
is not set for corotor2. They attach a "QC pass" sticker & they think is a good copy, but is not.

[lme]

I do have an old (china junk !) witch is rotating counterclockwise (from V-H!) instead clockwise (see servo1.mpg):

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The 2nd china junk is jumpy no matter what i adjust (see servo2):
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So, I guess there is no way to reset/adjust this servos. Every time i reposition the gear of the potentiometer it's reversing back to the factory position.
So far I'm using the original chaparral servo from the polarotor witch came with the dish.
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I'm waiting for a new chaparral servo hopping is not another china made copy !!

[el bandido]

IMO, that servo motor to rotate the probe is the ultimate for fine tuning. The problem though is it is outdated and no longer supported. It is also from a time where satellites had more issues with skew. Today, a dual lnb feed works better because thee are no moving parts to maintain. Best of luck on getting it fixed!

[lme]

IMO, that servo motor to rotate the probe is the ultimate for fine tuning. The problem though is it is outdated and no longer supported. It is also from a time where satellites had more issues with skew. Today, a dual lnb feed works better because thee are no moving parts to maintain. Best of luck on getting it fixed!

I understand that an orthomode feedhorn is more precise, but is hard to find a decent one as the market is flooded with china junk. Just an example is that DYNA servo: all holes are slotted just to make sure that can be installed. They do not care about the precise position of such device in the assembly. As for an original chaparral every hole is round & in the right spot. I just got my new chaparral servo today. pertaining the weather I'll try to replace it tomorrow.

[lme]

Well after waiting for better weather, today I manage to finish the setup. I decided to use the 8115 DRO norsat lnb for c-band instead of the old norsat gold, witch came with the dish. I preferred this DRO over a 5150F PLL i also have, but I had to use an elbow, so I can fit the cover.

[lme]

Finally after waiting for a better weather, Today I managed to finish the setup. I replaced the old norsat gold witch came with the dish, with a norsat 8115 DRO (3.4-4.2Ghz). Preferred this over 5150F PLL (3.7-4.2Ghz). I had to use an elbow so I can fit the cover over the corotor.
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[ArloG]

Until. Why not rotate the feed 90 degrees? Making H>V & V>H?
Or am I missing something?

[lme]

Until. Why not rotate the feed 90 degrees? Making H>V & V>H?
Or am I missing something?

So, when selecting a channel scanned on H tp, the servo will move the probe on V position and it will show nothing on the screen... I replaced the servo with a genuine chaparral on my old corotor 2, and looks like every thing is back to normal.
Had hard time to check the angle of the scalar to be parallel to the dish plate as the dish is high on the due south position.
My due south geo position is at 83°w, but AMC9 is not anymore there. I have AMC9 with a fake tp in my sat list, just to check what I need when the polar axis is at zenith. The closest sat is at 82°w (Bell), and is Ku, but there is signal on one tp I can use.