Best C-band 6' Dish Setup

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zamar23

zamar23

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Can you guys list a full set of recommended component models required to setup a motorized 1.8 m C-band BUD in a congested city conditions (including everything)?

Is it generally a good idea to transform it later to a C/Ku-band motorized reception set, and how it would change best components set selection and specs?
 
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pendragon

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If I recall, you were previously considering a mini-BUD for roof mounting. If you need to put a 6' on the roof, you'll probably want something fairly light and easy to mount. Are high winds a problem?

Sadoun sells a 1.8m dish that might fit the bill. I put one on the roof with a HH motor that is no longer available, but I'm sure an actuator would work about as well with the included polar mount. It doesn't require a massive pole and I have been able to get a lot of stuff, including some high SR S2. As it is a solid and reasonably shallow, it works fine for both C and Ku. My dual ortho feed works quite well on this dish and that's where it ended up after testing first on my 3m perf and 2.3m mesh (not that it didn't work better on those, but the Ku improvement wasn't terribly significant). There are far less expensive C/Ku integrated feeds and those would probably be more cost effective.
 
zamar23

zamar23

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Pendragon

As always, I appreciate your reply. I'm looking at option to go with a C/Ku-band prime focus 6-footer instead of an offset 4-footer - too many folks suggest this path. It will probably be a stand mounted, and the stand fixed to a concrete floor or a wooden pad. I was looking at Fortec prime focus 6-ft dish at Sadoun's site, and can't seems to figure out, how many actuators it needs for a motorized setup? I assume, one is needed to rotate its mount, another to adjust in synch its elevation angle, and the 3-rd to skew the LNB - is that right? What actuator models would be the best? Or, a motor can be found that would perform all 3 movements similar to Ku-band dish polar mount setup - are you saying, that's what you did, and using what exact H-H Motor model? Is there an analog to it now? What device would then control movement in synch of all 3 rotors - it looks like required power should be too high for a sat receiver to handle?

Also, looking at Chapparal CoRotor II Plus, it seems to be a good choice for that setup - is it? When you mentioned a Dual Ortho Feed, what model did you have in mind, and what exact LNB models to mount with that feed? Can it do both C and Ku band in both 2 Linear and 2 Circular? I wonder, will DMX741 Quad Polar C/Ku LNBF be a better choice, and can it be used in a motorized setup at all without a CoRotor? Should Skew angle be always the same for any C and Ku-band sats at the same orbital location?

That's amazing, no sponsor site gives as a sample a complete list of components required for a 1.8 m or similar BUD setup, and neither provides a schematics, full picture or drawing showing all of them connected.
 
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Mr Tony

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an actuator is to C-Band motorized what a motor is to KU Band motorized

It changes the dish elevation, azimuth and skew as it moves across the arc.
 
Anole

Anole

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Six foot Fortec Star prime focus dish, ready for an actuator (motor).
Geo-orbit site explains how the mounts work (see all four pages for the full story)
Actuator, or the motor to move the dish.
Motor controller; connects between receiver and LNB, accepts commands, and moves the dish.
The GeoSat C-band-only C2 LNBF is on sale, it'll feed two receivers, or with a multiswitch it can feed more receivers.
I've not seen any of the dual-band LNBFs perform well enough on Ku to want to put one on a six-foot dish, but if you do, the Ck-1 or DMX741 are good choices.
Other accessories like cable, grounding blocks, or switches would be on an as-required basis.

Hopefully, other members will add whatever I forgot, or describe alternate approaches.
As you see, this kit uses voltage-controlled feedhorn, not the co-rotor style.
Also, I did not address the reception of circular on C-band nor DBS Ku band.
I'm of the opinion that you cannot get everything on one dish. - :cool:
edit: well sure as hell not on a six foot dish!
 
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pendragon

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I was looking at Fortec prime focus 6-ft dish at Sadoun's site, and can't seems to figure out, how many actuators it needs for a motorized setup? I assume, one is needed to rotate its mount, another to adjust in synch its elevation angle, and the 3-rd to skew the LNB - is that right? What actuator models would be the best? Or, a motor can be found that would perform all 3 movements similar to Ku-band dish polar mount setup - are you saying, that's what you did, and using what exact H-H Motor model? Is there an analog to it now? What device would then control movement in synch of all 3 rotors - it looks like required power should be too high for a sat receiver to handle?

Iceberg covered this, but a dish rotating on a polar axis will automatically track the Clark belt meaning you only need one actuator or one HH motor to take care of elevation, azimuth and skew. Actually this isn't quite correct, but by employing a declination angle one can approximate this to, say, 0.01 degree or better and this is good enough.

Also, looking at Chapparal CoRotor II Plus, it seems to be a good choice for that setup - is it? When you mentioned a Dual Ortho Feed, what model did you have in mind, and what exact LNB models to mount with that feed? Can it do both C and Ku band in both 2 Linear and 2 Circular? I wonder, will DMX741 Quad Polar C/Ku LNBF be a better choice, and can it be used in a motorized setup at all without a CoRotor? Should Skew angle be always the same for any C and Ku-band sats at the same orbital location?

Corotors were great feeds in their day, but most current receivers cannot drive their skew adjustment servo. You can work around this but it can be a pain. Furthermore corotors are subject to losses, particularly on Ku, because of their design.

There are a number of C/Ku integrated feeds, some mentioned already by Anole. I don't have any direct experience but a lot of people here swear by them. Anecdotally I have heard more than a fair share of Ku performance complaints. However this could be caused by factors unrelated to the actual feed and LNBs.

I seem to recall that at one time you wanted to get both your subscription services and FTA from the same dish. That may be tricky, but I may have a solution. Neither corotors nor integrated C/Ku feeds can provide both linear and circular Ku reception. Dual orthomode feeds can't in their normal configuration, but there is a variation on something I have done that will work. If you get a dual ortho, you'll be out at least $200 for the feed itself (ADL probably).

Then you have to buy LNBs. Normally that would be two C and two Ku, but here's where life gets interesting. You still need the two C LNBs, and they will cost anywhere from $20 apiece (probably marginal) to $100 apiece (probably overkill). I started with two of the latter on my dual ortho plus the usual two Ku LNBs.

It worked fine, but then I decided to go for a universal Ku LNB and there wasn't much available with the correct flange. So I did a simple modification to the feed and instead bolted on an Invacom QTH-031 quatro universal LNB for Ku instead of the separate Ku LNBs. It works great.

If you want both circular and linear Ku, you could instead mount an Invacom QPF-031 in the same manner. That would give you linear C, linear Ku and Circular Ku out of the same feed and dish. All with very high performance. I know I've promised a thread on how to do this in the past, but I do have this Frankenstein feed up and running so pictures shouldn't be hard to come by.

To be fair you could alternately sidecar a circular Ku LNBF next to your C-band scalar, whatever it is, or even mill out a hole for it. That would probably work fine because circular Ku satellites have a ton of power and the underscan and off-axis losses would be more than made up.
 
zamar23

zamar23

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Thanks guys! Geo-Orbit is great.

I have heard more than a fair share of Ku performance complaints. However this could be caused by factors unrelated to the actual feed and LNBs.
Could you elaborate on that?

Still not sure, what model of dual ortho do you have in mind - can you give a link? Also, if CoRotor adjusts skew, why would one need it for a dish on a polar mount? Or its suited for a different mount type of a motorized C-band dish - which type? Keenly waiting for your closeup pics with Invacom mounted next to a C-band feed. Is it a 1.8 m dish, and how close range focal point of that dish affected designed for an offset dish Invacom's performance?
 
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pendragon

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Could you elaborate on that?

Since I never had an integrated C/Ku LNBF and am not planning on getting one, I don't pay much attention to the details. However there are a fair number of problems people report, particularly with the Ku side. Because these LNBFs are very inexpensive, it may simply be playing the lottery as to whether one gets a good one or not. On the other hand I believe a lot of BUDs are not the best match for Ku. The surface departures from a true paraboloid and/or irregularities may be fine for C, but not good enough for Ku. There is also the problem that there is no way to adjust the f/D for the Ku side of an integrated LNBF. I expect Ku is often under-illuminated on these feeds, particularly for deeper BUDs. Finally the narrow beamwidth on a BUD for Ku puts a very high premium on alignment that people may not be used to with C-band only. But with no information at all, I can only speculate why some people have problems with integrated C/Ku LNBFs

Still not sure, what model of dual ortho do you have in mind - can you give a link? Also, if CoRotor adjusts skew, why would one need it for a dish on a polar mount? Or its suited for a different mount type of a motorized C-band dish - which type?

Look for ADL-RP3-2-2B. Sometimes there are nice closeouts on this feed for low bucks.

A corotor has only one LNB for each band. It selects polarization by rotating C/Ku probes with a servo that is controlled by the receiver, and because newer receivers no longer support this you would need a workaround. This is old technology. Newer C/Ku LNBFs have multiple probes and switch polarization electrically. So for all but specialized applications, a corotor is not really used for adjusting skew, just polarization.

Keenly waiting for your closeup pics with Invacom mounted next to a C-band feed. Is it a 1.8 m dish, and how close range focal point of that dish affected designed for an offset dish Invacom's performance?

Yeah, me too. Work, kids and other emergencies always dominate. But I plan to do some work on this in the next 2-3 weeks. This dish is a 1.8m Fortec that has a f/D of 0.38, which seems good for Ku reception on a dual ortho. Note the Invacom LNB model I suggested does NOT have a feed built-in. So married up to my dual ortho feed, this is prime focus all the way.
 
zamar23

zamar23

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Thanks for clarification.
Still unclear, are there cases of a C-band sat having notably different skew angle requirement than a Ku-band sat in the same or close orbital location? How to deal with it? A polar mount dish, whether offset or prime focus, seems to have a little flexibility in such cases.

Could you elaborate a bit, exactly why you selected that particular feedhorn? It seems too short to me to allow notable adjustment to Invacom's focal point if at all possible. May be you can attach one pic as a "forward looking ad"? :)
 
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pendragon

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Thanks for clarification.
Still unclear, are there cases of a C-band sat having notably different skew angle requirement than a Ku-band sat in the same or close orbital location? How to deal with it? A polar mount dish, whether offset or prime focus, seems to have a little flexibility in such cases.

AMC 1 has a weird Ku polarization 'skew', but other than that every other bird I know has essentially the same direction of polarization relative to the orbital plane. Almost all FTA motorized dishes use polar mounts. This means you only need one actuator or motor to drive it across the Clark belt. Flexibility, other than AMC1 Ku, is unnecessary. One can live with AMC1 as the offset is considerably less than 45 degrees, or you can use a dedicated dish or toroid. I wouldn't buy a corotor for that application alone. The only other argument for a corotor would be to receive circular C-band in addition to linear C-band. There aren't many circular C-band satellites viewable in North America, so unless you have a desperate need, this also is likely not worth the pain.

Could you elaborate a bit, exactly why you selected that particular feedhorn? It seems too short to me to allow notable adjustment to Invacom's focal point if at all possible. May be you can attach one pic as a "forward looking ad"? :)

The focal point for any signal, whether C or Ku will be at the same point. A dual ortho feed has two waveguides from its mouth (at the focal point) for C and Ku back to the LNB probes. I wrote a separate thread on the mod. Promise kept.
 
zamar23

zamar23

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Thanks. It seems like you're saying, the adjustment of the Invacom's position is not required, you just use standard fixed length flange instead. If that's the case, why most dual C/Ku-band LNBs like DMX741 allow and designed with expectation of Ku-band LNB position being adjusted?
 
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pendragon

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Thanks. It seems like you're saying, the adjustment of the Invacom's position is not required, you just use standard fixed length flange instead. If that's the case, why most dual C/Ku-band LNBs like DMX741 allow and designed with expectation of Ku-band LNB position being adjusted?

I don't have a 741, but I expect it allows the Ku part to be rotated with respect to the C part so that both are properly aligned for H & V polarization (they should be the same direction but there are manufacturing tolerances after all). My dual ortho mod with the Invacom is no different. After I have H & V aligned for C by rotating the whole assembly in the scalar, I rotate the Ku waveguide with the Invacom on the back to peak the H & V alignment for Ku.
 
Anole

Anole

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On all the dual-band LNBF's I've seen (DMX741, Ck-1, BSC-621), the Ku LNB is not adjustable for skew relative to the C-band LNB.
They are fixed, and you adjust the entire feedhorn/LNB assembly for skew.

Most of the trouble in getting the Ku adjusted properly, is unrelated to skew.
It seems to be related to getting the assembly centered and perpendicular to the dish.
On C-band, some misalignment goes unnoticed.
On Ku, it cannot be tolerated (with these feeds).

Also, many of the LNBFs are not clearly marked for f/d, so you cannot set 'em and forget 'em.
If you move the entire feed/scalar assembly toward/away from the dish to adjust focus, you never know if you have the right f/d.
And if you have a fixed scalar, and move the LNBF in/out to achieve focus, you're just screwed! - :rolleyes:

From what I've seen, the best approach, is to mount the feedhorn to the dish, adjust for focus and centering, and -then- bring the scalar into play for best signal quality.
But, that is not how the hardware is designed... :(
 
zamar23

zamar23

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Are you guys saying that Ku-band LNB inside these dual C/Ku-band LNBFs can't be moved independently within the LNBF Ass. along its axis back & forward to find the best focal position for Ku-LNB only? Is there ever a need to move it, or another approach can be used to achieve the same result?
 

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pendragon

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Are you guys saying that Ku-band LNB inside these dual C/Ku-band LNBFs can't be moved independently within the LNBF Ass. along its axis back & forward to find the best focal position for Ku-LNB only? Is there ever a need to move it, or another approach can be used to achieve the same result?

Remember the mouth of the feed is roughly at the focal point of the dish, not the LNB. The feed acts as a waveguide, to some degree, which transfers the focused signal back to the LNB, whose probe is really the antenna. The length of the waveguide has nothing to do with adjusting the focal point, but it is important for other factors. Combo feeds have coaxial waveguides, the outer tube is for C and the inner for Ku, because waveguide diameter is critical to guiding a given frequency range with minimum loss. Thus the LNBs for both bands each have a waveguide from the focal point. There is no separate adjustment for C vs. Ku focus because positioning the feed's mouth is all you need to do.

The first diagram you posted is a little misleading because the focal point of a parabolic dish is in the same place for any signal frequency. You can even focus light if your dish is aluminized and fry your feed. The focal 'clouds' may be different because of imperfections in the dish, but the feed cannot take this into account. The optimal location of the feedhorn mouths for these clouds may be different for C and Ku, but that should be incorporated in the feed design. I'm not sure what the second and third pictures have to do with this; it looks like the second has a properly set f/D on the feed and the third is under-illuminating because the f/D is set higher on the feed than the dish's f/D.
 
zamar23

zamar23

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The length of the waveguide has nothing to do with adjusting the focal point, but it is important for other factors.
What factors? If Ku-LNB position can't be adjusted independently of C-LNB, then a corresponding cloud catching couldn't seems to be one of these factors?
 
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pendragon

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What factors?

There are more than I want to bother with, but here are a few that come into play when designing a feed waveguide:

1. Long enough to allow a given f/D adjustment range.
2. Short enough to minimize losses.
3. Capable of mounting LNBs so they don't interfere with each other, the scalar or the mounting arms.
4. Room for a dielectric or 1/4 wave plate for circular feeds.
5. Access to set-screws to adjust skew.

None of these have anything to do with focal point optimization, but are probably as or more important to a successful product.

If Ku-LNB position can't be adjusted independently of C-LNB, then a corresponding cloud catching couldn't seems to be one of these factors?

Designing a feed is not like designing a bookshelf. There is science, art and magic involved, and a feed designer is faced with constraints, optimizations, compromises and complex interactions, many of which s/he cannot control. An example might be the topologies of focal clouds, which will vary with the frequency, dish model, manufacturing tolerances and surface condition. We want one-size-fits-all, but that often means less than optimal performance. Some feeds may work better on certain dishes, but you won't know until you try. Fortunately the differences are usually not important.

Modern feed design is best done by computer simulation rather than cut-and-try. This allows the balancing of conflicting factors, some of which are hard to measure. A few gross adjustments are possible with feeds, but building a feed with separately adjustable mouths for C and Ku sounds like a theoretical and mechanical nightmare to me. Adjusting one relative to the other is going to have complex positive and negative effects on both, many of which cannot be measured by typical FTA users. The more adjustments you provide to a lay person, the more likely they will screw it up to the point that nothing works.

My advice is to be happy and not to worry. A good feed will take the necessary factors into account and do a good job optimizing very complex demands. Your job is to adjust your dish to track the arc accurately, ensure the feed horn is in the right place, set the f/D and polarization skew correctly, choose LNBs that meet your performance requirements and have a switching/distribution system that causes minimal distortions and CNR losses to the signals. A lot of people here work hard to get all of these right, but there is so much room for errors that I would not be surprised if many FTA systems are not delivering their full potential. Any single factor I just described will have far more to do with enjoying good reception than feed design details.
 
zamar23

zamar23

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Thanks for the advice. I'm getting happier every day. :)
 
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