Aiming and peaking a C-band LNB - more guesswork than science?

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ancient

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May 12, 2014
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To me the most mysterious part of setting up a new dish is peaking the LNB. I read a lot of posts where people say that you have to aim the LNB precisely at the center of the dish, and that it should be an exact distance from the center. But this gets complicated by several factors that to me make this seem more like guesswork than science.

The first problem is that many LNB's and scaler rings are manufactured to very sloppy tolerances. It should not be possible to put an LNB into its matching scaler ring and aim it 15 or 20 degrees off center but unfortunately that is all too possible with some modern LNB's. So even if you get the scaler ring precisely centered somehow, you still have no idea if the LNB is centered since it can flop around inside the ring.

I have wondered why someone does make a small ring that would snap around the outside of an LNB, similar to the way a pair of headphones fits around your head (so it would fit LNB's of slightly varying sizes snugly), with about 8 laser LED's around the outside that all point straight down toward the center of the dish. If there is no way to make such a thing with enough precision to give good aim, then you understand why I say that trying to aim at the center is more guesswork than science.

I see people suggest a string test, for example to make sure the scaler ring is at an equal distance from the edge of the dish on all sides, or that the outer rim of the LNB is. First of all, I would love to know where people are getting this non-stretchy string that can measure with such great precision. Even kite string or fishing line will stretch a little when you pull on it and if you pull a little harder on one side than the other, your scaler ring or LNB will be off a little. And that assumes that you can attach the string at the exact same place for each measurement. And that when you get it right and go to tighten it down, nothing moves.

Then there is the problem of the support arms being a little to short or a little too long. Usually when you buy a LNB they do not give you very long bolts or screws for attaching the scaler ring, so you MIGHT get a couple washers between the scaler ring and the supports, but that's about it. And nowadays they may be using some weird metric bolt that would be difficult to find in a longer length in an American hardware store.

So then you do the calculation to figure out how far the LNB should be from the center of the dish, and where it should be in relation to the scaler ring. Some dishes have a bump or a metal plate in the center, so do you adjust for that? And where do you measure to on the LNB? The outer rim? The back of the throat (as if I really want to take that protective cover off and jab a metal tape measure in there!)? I don't know why LNB manufacturers don't inscribe some kind of measure line on the outside of the LNB, so you know where you're supposed to be measuring from. Or at least put a diagram on the box so you know where to measure from. I see some documents, probably written when most people were using Chaparral feedhorns with bolt-on LNB's, that suggest some fraction of an inch. I seriously doubt that's the same measurement that should be used with an integrated LNB that's made in a country that uses the metric system.

So in my experience, if you carefully measure everything and you think it's all correct according to the calculated values, if you then loosen the bolts on the scaler ring and slide the LNB in and out and maybe twist it a little you can gain five or ten more points of signal quality. The setting on the side of the LNB is nowhere near what it should be according to your calculations, but that's where it winds up getting the best signal. In almost every case but one or two, I have found that sliding the LNB in a little closer to the dish improves the signal. Of course the whole time you are doing that you're fighting to keep it straight because of the aforementioned slop between the outer diameter of the LNB and the inner diameter of the scaler ring. Sometimes it seems like trying to keep a pencil centered in a doughnut hole.

And of course while doing that you are also trying to check for the best skew angle. I honestly don't know how anyone gets this right. I have never put up a dish where I have been truly happy about the final position of the LNB, even in the couple of cases where I spent several hours trying to get it right.

If C-band enthusiasts were a bigger market I'm sure someone would come out with some kind of aiming aid that would make this process easier, especially with the newer integrated LNB's. Right now it seems more like intuition and trial-and-error than science. Then again, if they did it would probably be too expensive for many of us, and it would be complicated by the different types of LNB mounts (3 arms, 4 arms, buttonhook, etc). But to me, this is the most frustrating part of aiming a dish. You'd think it would be dead simple, and it might be if everything was manufactured to precision tolerances, but unfortunately that's rarely the case.

What I suspect is that a lot of guys do everything "by the book" and don't take into account that the measured distance to the center of the dish might be a significant distance closer or further than the reflective center of the dish, especially if there's a bump or metal plate there. Or that on LNB's you're not told where on the feedhorn you should be measuring to. Or that string is stretchy, or that the outer rim of the dish might be a little warped and throw off all those careful measurements. As I say, I've picked up four or five points just by loosening the bolts on the scaler ring and moving the LNB around by hand, to a place where the calculations say is all wrong, but nevertheless my receiver is showing improved signal strength and/or quality. I don't know if you guys have any secrets for doing this correctly but if you do, and they don't cost an arm and a leg, I would love to hear them.

One other thing, I have seen it suggested a couple of times to use a cheap ruler with a laser pointer to aim the LNB at the dish center. For the life of me I cannot visualize how this would work. If someone could post a picture or video of how this is done, it would be very helpful, because at the moment I don't understand that at all, unless maybe you guys are using some kind of ruler I've never seen before.
 

jasjas

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I have thought about machining the back of the scaler ring flat then mounting a 2 x 2 x 3 long aluminum angle to the back of the scaler and use a large hose clamp around it and the lnb.
then the lnb would sit in a V and doses not flop around when adjusting and tightning.
that takes care of the massive hole that is needed for the lnbs that have that outer lip.
another way would be to make a flat plate with the V mounted to it and mounted to the struts so the scaler can be adjusted independantly instead of being fixed to the struts.
the scaler or mount would still have to be made square and centered to the dish.
but adjusting to get every bit of signal would be easyer and faster.
 

RimaNTSS

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Aug 9, 2013
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jasjas, I think you mean something like this IMG_20161127_193654 (Custom).jpg IMG_20161127_193703 (Custom).jpg IMG_20161127_194125 (Custom).jpg I've made it some time ago.
 

wvman

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I just went after a dish that had a scalar and feed where the tolerances were so close I could not get them apart until I soaked them with penetrating oil. Once I got them loose, it was a dream to move the feed in and out and rotate it left and right. You are right, the new feed assemblies are very sloppy and usually present problems when trying to precisely align the feed. However, we cannot expect precision on a piece that cost under $50.

I've been thinking of machining a two piece bushing that would be held together by a couple small set screws to take up the slack and provide a smooth, flat surface for the set screws in the scalar to tighten against. The scalar that was on the old dish would have worked with the Titanium LNBF, but for some reason, these feeds have a ridge around the outer edge of the feed that does not allow it to be inserted into the old scalar.

I checked the outside diameter of the new feed, which ended up being almost the same diameter as the old one, but the ridge prevented it from going in. I was going to play with it to see how the new feed performed with the old scalar, but of course, you wouldn't be able to use the FD marks for setting it. You never know what works until you try new things. I'm sure the slop was built in to allow for offsetting the feed to compensate for focal point being slightly off center.
 

richyrich

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Dish shape determines all adjustment's to any parts you place onto them; that every dish is different means any one dish must be different than any other; but free to air satellites/frequencies available do not change; they are stuck within the range they are used and planned for; that any dish receives them if you experiment; you will always find one dish to be better or worse at receiving them. Offset's to the center using the center of the dish accrue az and el at the same time; required for maximum gain in a direction. Thinking of the dish as a mirror allows the small adjustment's your assembly can make. Just try to remove the shadows each of the scalar ring's are doing when in perfect center focus (center of dish); the more you mount the more shadow shows in the meter; where VSWR is measured (shadow's of the aimed dish) are detected like tree limb's and even grass or mount bolts and other lnbf's mounted in the way of the dishes aiming ability)...
 

sgs

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Sep 27, 2012
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Southwestern Ontario
While that gear is super cool, I still see too many people trying to peak a dish using a STB instead of a proper meter.

I completely agree. When I first started out, I didn't have a meter, and there were certain signals I had a lot of trouble tuning. Once I got a meter, it helped me tune those signals easily.

sgs
 
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sgs

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Sep 27, 2012
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Southwestern Ontario
The first problem is that many LNB's and scaler rings are manufactured to very sloppy tolerances. It should not be possible to put an LNB into its matching scaler ring and aim it 15 or 20 degrees off center but unfortunately that is all too possible with some modern LNB's. So even if you get the scaler ring precisely centered somehow, you still have no idea if the LNB is centered since it can flop around inside the ring.

Take electrical tape, wrap it around the LNBF. Usually three or four times is the right thickness.

LNBFs usually come with some black rubber tape (often they stick it to the dielectric plate for shipping). That's supposed to be used on the LNBF to help center it. But wrapping electrical tape completely around the LNBF is easier, at least in my experience.

I have wondered why someone does make a small ring that would snap around the outside of an LNB, similar to the way a pair of headphones fits around your head (so it would fit LNB's of slightly varying sizes snugly), with about 8 laser LED's around the outside that all point straight down toward the center of the dish. If there is no way to make such a thing with enough precision to give good aim, then you understand why I say that trying to aim at the center is more guesswork than science.

They used to make a pointer device that basically had a plastic "cup" on one end and a metal rod that extended out the other end. The plastic "cup" end would go over your feed (LNBF), and was tapered to support multiple sizes of feed. The rod extended and pointed accurately enough at the center of the dish when aligned. I have one, but can't find any pictures online, and I'm too tired right now to take a pic and post it. It works really well and doesn't require batteries or laser pointers that get loose!

I see people suggest a string test, for example to make sure the scaler ring is at an equal distance from the edge of the dish on all sides, or that the outer rim of the LNB is. First of all, I would love to know where people are getting this non-stretchy string that can measure with such great precision. Even kite string or fishing line will stretch a little when you pull on it and if you pull a little harder on one side than the other, your scaler ring or LNB will be off a little. And that assumes that you can attach the string at the exact same place for each measurement. And that when you get it right and go to tighten it down, nothing moves.

Use fishing line, stretched across face of dish (and taped with duct tape), to help determine f/D ratio by measuring depth of the dish (often referred to as measurement "c"). Do not use string or fishing line to measure to the scalar ring, just use a tape measure and another person/helper when measuring that. The precision of the tape measure will be close enough to tell you if the arms are not the same distance to the scalar - which tells you the scalar isn't "flat" facing the dish surface. Obviously, tighten down the scalar to the support arms before measuring. It's easy to loosen one or two at a time to adjust, and re-measure.

So then you do the calculation to figure out how far the LNB should be from the center of the dish, and where it should be in relation to the scaler ring. Some dishes have a bump or a metal plate in the center, so do you adjust for that? And where do you measure to on the LNB? The outer rim? The back of the throat (as if I really want to take that protective cover off and jab a metal tape measure in there!)? I don't know why LNB manufacturers don't inscribe some kind of measure line on the outside of the LNB, so you know where you're supposed to be measuring from. Or at least put a diagram on the box so you know where to measure from. I see some documents, probably written when most people were using Chaparral feedhorns with bolt-on LNB's, that suggest some fraction of an inch. I seriously doubt that's the same measurement that should be used with an integrated LNB that's made in a country that uses the metric system.

If the metal plate at the center of the dish bulges out / has a "bump", just measure from the edge of the plate (3-4 inches from center). It won't be substantially different length. If that isn't satisfactory, take the plate off and get something flat to measure against. As you point out, it should be measured from the surface of the dish, not one or two inches from the surface.

The general consensus is to measure focal distance from surface of dish to 1/4 inch inside the lip of the LNBF. I could debate that, from my reading of all the old usenet newsgroup posts and other resources it might actually be 1/4 wavelength for c-band, not 1/4 inch. But just measure to 1/4 inch inside the LNBF, and be happy!

So in my experience, if you carefully measure everything and you think it's all correct according to the calculated values, if you then loosen the bolts on the scaler ring and slide the LNB in and out and maybe twist it a little you can gain five or ten more points of signal quality. The setting on the side of the LNB is nowhere near what it should be according to your calculations, but that's where it winds up getting the best signal. In almost every case but one or two, I have found that sliding the LNB in a little closer to the dish improves the signal. Of course the whole time you are doing that you're fighting to keep it straight because of the aforementioned slop between the outer diameter of the LNB and the inner diameter of the scaler ring. Sometimes it seems like trying to keep a pencil centered in a doughnut hole.

As I mentioned above, you can use electrical tape to "beef" it up. Of course, you may need to cut the tape so you can still see the f/D ratios stamped on the side of the LNBFs, so it might take some work. But really, if you know the f/D ratio, then look at the back of the scalar ring and align the outermost part of the back of the scalar ring to the f/D ratio stamped on the LNBF. You're now within about 1/4 inch of it being correct even with the worst scalar ring and LNBFs you can find. The slop here has more to do with the stamping on cheap LNBFs not being clear what line is for what f/D number. If you're using good stuff like Chaparral scalar and LNBs, then it's an exact measurement and is documented.

And of course while doing that you are also trying to check for the best skew angle. I honestly don't know how anyone gets this right. I have never put up a dish where I have been truly happy about the final position of the LNB, even in the couple of cases where I spent several hours trying to get it right.

Easy! Point your dish due south. The vertical antenna on the LNBF must be placed vertical and the horizontal antenna on the LNBF must be placed horizontal. Take the plastic cap off your LNBF and look inside, you'll see the two antennas. Notice that the heat sink / outside "square" part is at 45 degrees to the two antennas. When you're standing in front of the dish, looking at the face of the dish, with the dish facing due south, that "square" part of the LNBF should be between 3 and 6 o'clock. In other words, if you have four feed support arms and they are at 12, 3, 6, and 9 o'clock when facing due south, then the actual antennas inside the LNBF will exactly line up with the 3 and 6 o'clock feed arms.

If C-band enthusiasts were a bigger market I'm sure someone would come out with some kind of aiming aid that would make this process easier, especially with the newer integrated LNB's. Right now it seems more like intuition and trial-and-error than science. Then again, if they did it would probably be too expensive for many of us, and it would be complicated by the different types of LNB mounts (3 arms, 4 arms, buttonhook, etc). But to me, this is the most frustrating part of aiming a dish. You'd think it would be dead simple, and it might be if everything was manufactured to precision tolerances, but unfortunately that's rarely the case.

The real problem is that we want everything as cheap as possible, since we're just enthusiasts, so we don't buy a single engineered solution that precisely works together among all of the components. We mix and match and are satisfied buying a $50 LNBF and matching it up with a cheap knock off scalar ring, attach it to a dented up dish, don't check that the dish is warped, don't measure anything, don't take the time to understand why or how it works, and yet, despite that, still we mess around with it and get a signal. :)

What I suspect is that a lot of guys do everything "by the book" and don't take into account that the measured distance to the center of the dish might be a significant distance closer or further than the reflective center of the dish, especially if there's a bump or metal plate there. Or that on LNB's you're not told where on the feedhorn you should be measuring to. Or that string is stretchy, or that the outer rim of the dish might be a little warped and throw off all those careful measurements.

If the outer rim is warped, then the string test fails when you try to determine the depth of the dish - the strings will be moving each other or will be far apart. At that point you know you have a compromised dish and have to deal with it, understanding that if you put it up as-is, your measurements are compromised because it's no longer reflecting the signals to the focal point at exactly the same time.

As I say, I've picked up four or five points just by loosening the bolts on the scaler ring and moving the LNB around by hand, to a place where the calculations say is all wrong, but nevertheless my receiver is showing improved signal strength and/or quality. I don't know if you guys have any secrets for doing this correctly but if you do, and they don't cost an arm and a leg, I would love to hear them.

I think you need to tune your dish better or validate your measurements and calculations. Depending on the quality of the dish, scalar, and LNBF, that will limit what you can achieve with it. Along with all the usual issues like terrestrial interference, etc.

I've tried to point out a few things in this reply, hopefully it helps you or someone else reading it. Once the enthusiast understands the principles involved, and take the time to measure, adjust, etc., and grab a signal meter for final tuning, they will find it's quite enjoyable to set up a dish. Like any hobby, you have to spend lots of time learning / practising to get good at it.

sgs
 

sgs

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Sep 27, 2012
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Southwestern Ontario
They used to make a pointer device that basically had a plastic "cup" on one end and a metal rod that extended out the other end. The plastic "cup" end would go over your feed (LNBF), and was tapered to support multiple sizes of feed. The rod extended and pointed accurately enough at the center of the dish when aligned. I have one, but can't find any pictures online, and I'm too tired right now to take a pic and post it. It works really well and doesn't require batteries or laser pointers that get loose!

Just a follow up - I've posted pics of this feedhorn alignment tool in the thread called "Need SatelliteGuys Assistance for C-band Feedhorn Alignment Tool Project" : http://www.satelliteguys.us/xen/thr...-band-feedhorn-alignment-tool-project.328427/

sgs

Admin Note: Direct link to post: http://www.satelliteguys.us/xen/posts/4008645/
 
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wvman

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I made this device to find the optimum position by coincident movement for the scalaring and the position of the lnb in the scalaring .
First use the laser for the correct aiming point .
Once noticed the best signal , I change the device for the original scalaring .

View attachment 122704

View attachment 122706

View attachment 122707

Isn't it amazing the lengths we'll go to in order to have television. :) That's an impressive device to say the least. I have a meter with a spectrum analyzer that I use to locate the proper satellites. The signal meter is very sensitive and the least bit of movement is registered. It has a lock feature so you can save your original data so you can compare it with your final adjustments, or to return to your original settings if it happened to be the optimal position for the feed assembly.

When I first bought it, I didn't consider the fluctuation in signal as being clouds passing in front of the dish because I didn't realize just how sensitive it actually was. I did most of my tuning on cloudless days when possible in order to eliminate the cloud factor. The fluctuation on heavily clouded days could be substantial, but you could get an average and work around it. Anyway, nice going. It's pretty impressive and well designed.
 

wvman

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Ancient,
"The first problem is that many LNB's and scaler rings are manufactured to very sloppy tolerances. It should not be possible to put an LNB into its matching scaler ring and aim it 15 or 20 degrees off center but unfortunately that is all too possible with some modern LNB's. So even if you get the scaler ring precisely centered somehow, you still have no idea if the LNB is centered since it can flop around inside the ring."

That's precisely why I save the old scalars off every dish I pick up. The tolerances are much better and the only problem I encounter is the ridge around the outside of the throat on the LNBF. I recently cleaned up a Chaparral Gold scalar to use with a WS International LNBF. In order to get it inside the Gold scalar, I had to remove the ridge around the throat of the LNBF. (I'm not sure why that's there considering the sloppiness of the fit to the provided scalar. Maybe for strength perhaps).

I use three stainless steel hose clamps screwed together, with the adjustment nuts 60 degrees apart around the outside of the feed in order to keep the feed square in the scalar when setting the focal distance. The clamps allow you to butt the feed up against the tightening nuts them so you can tighten the screws down in order to keep it accurately aligned on the fd marks. Maybe Titanium could shed some light on why the scalar has so much slop around the feed assembly. I'd like to know if they will warranty a LNBF that has the ridge removed.

If you've never used a WS International feed, you probably wouldn't like them. It only has 1 tightening screw in the scalar and the feed sets off center almost a half inch. it butts up against a couple blocks on the opposite side. A really poor design as far as I'm concerned.
 

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sgs

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I recently cleaned up a Chaparral Gold scalar to use with a WS International LNBF. In order to get it inside the Gold scalar, I had to remove the ridge around the throat of the LNBF.

I've also had to remove the ridges on various LNBFs to get them to fit in older scalar rings. Bench grinder works well and much easier than filing by hand. :)

sgs
 

Titanium

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Having installed and serviced thousands of dishes, I never gave much thought to the need to have a close mechanical tolerance between the feedhorn and scalar opening before adjusting and tightening the set screws. We would mix and match different manufacturers and models components and simply optimize the position and alignment as part of the tuning process. Yes, I have cut feedhorns and bored scalars! :) Never trusted that the feedhorn would natively set at the correct angle even if doing a new install using parts from the same manufacturer. I agree that a 3 point set screw configuration is superior to a single set screw.

Would I offer a refund on a modified feedhorn? Not likely. Would I replace under warranty a modified LNBF feedhorn which electronically failed? Yes, the two are unlikely related unless the cut-off filings got ito the electronics cavity!

Aiming and peaking C-band is a science. Once you exhaust the science, freelance to optimize for your system anomalies... :D

BTW... I understood the amalgamated rubber tape was to secure the dielectric slab into position (if used). :confused:
 

wvman

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Having installed and serviced thousands of dishes, I never gave much thought to the need to have a close mechanical tolerance between the feedhorn and scalar opening before adjusting and tightening the set screws. We would mix and match different manufacturers and models components and simply optimize the position and alignment as part of the tuning process. Yes, I have cut feedhorns and bored scalars! :) Never trusted that the feedhorn would natively set at the correct angle even if doing a new install using parts from the same manufacturer. I agree that a 3 point set screw configuration is superior to a single set screw.

Would I offer a refund on a modified feedhorn? Not likely. Would I replace under warranty a modified LNBF feedhorn which electronically failed? Yes, the two are unlikely related unless the cut-off filings got ito the electronics cavity!

Aiming and peaking C-band is a science. Once you exhaust the science, freelance to optimize for your system anomalies... :D

BTW... I understood the amalgamated rubber tape was to secure the dielectric slab into position (if used). :confused:

I never meant to give the impression that I would send a modified feed horn back for a refund. I was only interested in finding out if it failed electronically if it would be covered under warranty. I always figured it would be easier to find center using the screws holding the scalar to the feed legs than trying to adjust and readjust the feed by altering the position inside the scalar. BTW, did you see the photo of the feed alignment tool I made last month to set the polarity and center the feed?

Not exactly a work of art, but it serves the purpose. :) I'm working on another project right now. I found another 10 foot dish that has some questionable feed support legs. A couple are cracked near the scalar and the others are pretty rusty. You can see where they had water in them. Three of them have stress cracks in them where the water froze inside them. I'm making new supports out of 1', sixteen gauge square aluminum tubing. I haven't welded aluminum in years and it's turning out to be a bit of a challenge.

I found out that a little soft rubber connector seal works good at securing the dialectric plate, although, I never saw one loose enough to fall out, but I rarely use it anyway. I don't see much up there that interest me that's circular polarization. Thanks for the input. Answered my questions. :)
 
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ancient

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May 12, 2014
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Interesting to see some of the ways you guys deal with these problems.

Just a follow up - I've posted pics of this feedhorn alignment tool in the thread called "Need SatelliteGuys Assistance for C-band Feedhorn Alignment Tool Project" : http://www.satelliteguys.us/xen/thr...-band-feedhorn-alignment-tool-project.328427/

sgs

Admin Note: Direct link to post: http://www.satelliteguys.us/xen/posts/4008645/

Wish you could still buy those. I suppose today you could maybe make the plastic part of one of those tools with a 3D printer, provided you have access to one, and know how to fabricate parts that can be printed using it. If you don't have a 3D printer, but have some chunks of old 4x4 lying around, it might still be possible to make one if you could find a Forstner bit of the exact same size as the outer diameter of your LNB (to slip over the outside of the LNB like that one does), or a hole saw that would drill out a core exactly the size of the inner diameter of the LNB (to slip it inside the LNB throat, though I'd be nervous about damaging the LNB if doing that). But if the end is fluted then you have to take that into account too, and I imagine it might be pretty difficult to find a Forstner bit or hole saw of exactly the right side for a given LNB. And while it's not that hard to find a piece of solid or threaded rod to stick out of the end, I just wonder how you'd get it to point precisely at the center of the dish. Of course, if you really wanted to make something using wood or a block of hard plastic that would slip inside the LNB throat, then a lathe would probably be the best tool to use, but not many of us have one of those in our sheds or garages.

Ancient,
"The first problem is that many LNB's and scaler rings are manufactured to very sloppy tolerances. It should not be possible to put an LNB into its matching scaler ring and aim it 15 or 20 degrees off center but unfortunately that is all too possible with some modern LNB's. So even if you get the scaler ring precisely centered somehow, you still have no idea if the LNB is centered since it can flop around inside the ring."

That's precisely why I save the old scalars off every dish I pick up. The tolerances are much better and the only problem I encounter is the ridge around the outside of the throat on the LNBF. I recently cleaned up a Chaparral Gold scalar to use with a WS International LNBF. In order to get it inside the Gold scalar, I had to remove the ridge around the throat of the LNBF. (I'm not sure why that's there considering the sloppiness of the fit to the provided scalar. Maybe for strength perhaps).

I always was under the impression that the scaler rings and LNB's were kind of a matched set. Is that not the case? I have a few old feedhorns with scalers from the analog days lying around.

I use three stainless steel hose clamps screwed together, with the adjustment nuts 60 degrees apart around the outside of the feed in order to keep the feed square in the scalar when setting the focal distance. The clamps allow you to butt the feed up against the tightening nuts them so you can tighten the screws down in order to keep it accurately aligned on the fd marks.

Now that is a brilliant low-tech solution. I have a whole plastic bin full of various sizes of hose clamps so I'm definitely going to try putting something like that together when I start working on my dishes again.

Maybe Titanium could shed some light on why the scalar has so much slop around the feed assembly. I'd like to know if they will warranty a LNBF that has the ridge removed.

If you've never used a WS International feed, you probably wouldn't like them. It only has 1 tightening screw in the scalar and the feed sets off center almost a half inch. it butts up against a couple blocks on the opposite side. A really poor design as far as I'm concerned.

We'll have to agree to disagree on that point, because personally I've never had anywhere near as much trouble getting the ones with the single screw set in place, and I've always felt the three screws were the worse design. To me, the fact that the LNB body was sitting up against a couple of small vertical ribs, or what you call blocks, on the inside of the scaler ring collar made it much easier to keep the LNB relatively straight, as opposed to if you are trying to tighten three set screws with a relatively small contact area inside a loosely-fitting collar. I'm not saying those ribs were sufficient to keep the LNB body perfectly straight in the scaler, but at least it felt like I was at a better starting point. But then again, it never occurred to me to try the hose clamp trick, so maybe that makes all the difference. To each his own, I guess, but personally I rather dislike the three screw design.
 

wvman

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Interesting to see some of the ways you guys deal with these problems.



Wish you could still buy those. I suppose today you could maybe make the plastic part of one of those tools with a 3D printer, provided you have access to one, and know how to fabricate parts that can be printed using it. If you don't have a 3D printer, but have some chunks of old 4x4 lying around, it might still be possible to make one if you could find a Forstner bit of the exact same size as the outer diameter of your LNB (to slip over the outside of the LNB like that one does), or a hole saw that would drill out a core exactly the size of the inner diameter of the LNB (to slip it inside the LNB throat, though I'd be nervous about damaging the LNB if doing that). But if the end is fluted then you have to take that into account too, and I imagine it might be pretty difficult to find a Forstner bit or hole saw of exactly the right side for a given LNB. And while it's not that hard to find a piece of solid or threaded rod to stick out of the end, I just wonder how you'd get it to point precisely at the center of the dish. Of course, if you really wanted to make something using wood or a block of hard plastic that would slip inside the LNB throat, then a lathe would probably be the best tool to use, but not many of us have one of those in our sheds or garages.



I always was under the impression that the scaler rings and LNB's were kind of a matched set. Is that not the case? I have a few old feed horns with scalers from the analog days lying around.



Now that is a brilliant low-tech solution. I have a whole plastic bin full of various sizes of hose clamps so I'm definitely going to try putting something like that together when I start working on my dishes again.



We'll have to agree to disagree on that point, because personally I've never had anywhere near as much trouble getting the ones with the single screw set in place, and I've always felt the three screws were the worse design. To me, the fact that the LNB body was sitting up against a couple of small vertical ribs, or what you call blocks, on the inside of the scaler ring collar made it much easier to keep the LNB relatively straight, as opposed to if you are trying to tighten three set screws with a relatively small contact area inside a loosely-fitting collar. I'm not saying those ribs were sufficient to keep the LNB body perfectly straight in the scaler, but at least it felt like I was at a better starting point. But then again, it never occurred to me to try the hose clamp trick, so maybe that makes all the difference. To each his own, I guess, but personally I rather dislike the three screw design.

I think the three screw design would be a lot better if the tolerances between the feed and scalar were narrowed down considerably. The hose clamps work really well because you have three points on which the feed rest against the scalar, and you can pre-set it to the correct fd before you mount the assembly on the feed legs. Then is a simple matter of loosening one of the screws in order to rotate the feed to the proper polarity. However, if you need to slide the feed closer to the dish, the clamps would be in the way.

After 30 years in the business, I've seen so many different ways to accomplish the same thing, I lost count. I guess whatever works for the person doing it is all that matters. :) I've been fooled a couple times when an idea someone had looked totally ridiculous and actually turned out to be a real time saver. I don't know if you remember the days when the dish was actually a gadget that looked like a backstop at a baseball game when you actually moved the feed rather than the dish.

That was always a trip considering all the adjustments were on the feed pole that stuck in the ground in front of the dish. Ah, the good ole days. :) Anyway, everyone has their preferences and that doesn't make one work any better than the other. I better shut up, I'm telling everyone how old I am. :) Cheers, and thanks for the reply.
 
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