Galaxy18 & Amc21 On One Dish!(2 Lnb's)

[stbel55]

Hello everyone, I have 33" dish and while locating AMC21 ( 125 ) I scanned Galaxy18 ( 123 ) and kinda liked some of the programs and feeds. I have AMC21 locked in at 63 Quality and even receive PBS Montana!! My question is I have second 10750 Linear LNB on bracket and am trying to catch Galaxy 18 being that it is only a 2 degree difference east a 3 degrees elevation. (??which side should I have the second LNB on??) Thanks for any advice or tips!!! PS Nice new website WOW!!

 

[bpalone]

You will need to pick a different second satellite, as you need a minimum of 3 degrees separation. Unless you are willing to do some handy work and sand/grind the LNBs so that you can get them close enough. I don't have the thread, but it has been done. I wouldn't do it, but I don't like doing experiments that could possibly cost me a couple of LNBs.

I'm sure others will hop in here with further advise.

 

[carlospr43]

NoN Credit for the job, I just kept a copy in my computer and just posted them

 

[Mr Tony]

the issue Carlos is that was on a 1.2 meter dish which 2 degrees CAN be done pretty easily
on a 33-36" dish the minimum is usually 4 degrees difference...

 

[Mr Tony]

Here is an example of 4 degrees (well 3.8) on a 1.2 meter dish and 4 degrees on a 36" dish (the 2 LNB's in the middle)

The larger the dish size the further apart the LNB's have to be.

 

[jorgek]

You could try pointing the dish right between the 2 sats and blind scan. It works especially with strong transponders.

 

[FaT Air]

I vote for aiming midway between the two and hoping to get them both. Should be possible because a 33 inch dish beamwidth is pretty 'wide'. But the caveat is, most on 125W is DVB-S2, so may not have much leeway in how much signal can be 'given up' and still perform.

 

[stbel55]

thanks for good advice everyone! I think I'm going to move the dish 1 degree east to split both signals and position the lnb's as close as I can without major modifications!! Wish me luck eh!!!!

 

[Titanium]

The idea of splitting the satellite positions then placing two regular KU LNBFs with full size scalars will not likely provide good results. On this dish the closest that two LNBFs with standard scalars will be about 6 degrees. Even if the 40mm housings were removed and the scalars cut, the standard 23mm feedhorns would need to machined to be conjoined.... even closer than the examples shown above in the WescoPC project.

Splitting the satellite positions and placing two LNBFs side by side will move the LNB feedhorns even further away from the convergence point (sweet spot) than if you only use a single LNBF. You might experiment with moving a single LNBF closer or further away from the reflector. At a point you may find that the two satellite signals may converge in a tighter pattern than at the dish's original focal distance. The loss incurred by moving the manufactured focal distance towards or away from the reflector might be less than moving the LNB feedhorns to the left or right sides of the sweet spot.

It is all smoke, mirrors and theory...

 

[stbel55]

I've been trying to find a picture I saw on the internet a while ago that showed the way the dish reflects the sat signal to the lnb. I think it does a cross over and I'm not sure which side to put the lnb on that is not centered. ( I'm going to leave the one fixed in the middle for amc21 62percent locked ) and try moving the 2nd one to find that sweet spot for galaxy18. But I'm not sure if it should be on the left or right of center lnb?? Does anyone have some kinda diagram that shows the way the sat signal comes in and reflects to the lnb!!! Thanks in advance

 

[FaT Air]

If, when looking out into space, the satellite is right of the prime 'target' the LNBF would be on the right of the prime lnbf when facing the dish face. (IT's like a mirror)

 

[carlospr43]

I've been trying to find a picture I saw on the internet a while ago that showed the way the dish reflects the sat signal to the lnb. I think it does a cross over and I'm not sure which side to put the lnb on that is not centered. ( I'm going to leave the one fixed in the middle for amc21 62percent locked ) and try moving the 2nd one to find that sweet spot for galaxy18. But I'm not sure if it should be on the left or right of center lnb?? Does anyone have some kinda diagram that shows the way the sat signal comes in and reflects to the lnb!!! Thanks in advance

I will say on the left side just a bit lower looking the dish from the front

 

[richyrich]

I you change the angles the lnbfs hold to the dish; you can even make the lnbf point at any angle of satellites when you multi-sat "set" them by aiming the lnbf; You even can if you leave the dish alone and only aim the lnbf's so they are angled to whatever degree you want; compared to the dishes reflection angles which are used when they are side by side (the dish reflects the second to the second point and the first to the first). Like an old side by side Ku/C lnb feedhorn assembly; you aimed the ku lnb to the satellite the c band was picking up so you only had to program one position and both lnb's received the same sat.

my link to multi-sat sets will probably be hit but so what http://richtv.net/commercial.html

What I need is a good picture of those Toroidial satellite dishes. They do multi-sats also; and the angles are excruciatingly a pain to line up; but they work!

Great work, by the way. great pics too!

And if you take your dish and mount it upside down; both lnbf angles will be reversed; and they will still pu the same 2 sats! The problem will be in skew; and you will have to skew the dish for other sats. If you mount another lnbf; it ; will pu 97 when set at the right placement and line. 97/99/101 would be pretty good; but each skew, each angle, will need perfect "sets" of your dish, the lnbf's; and those are what you can change.

I have personally mounted ku sat dishes upside down; sideways; in-between; and each receive the satellite signal; only the dish; and linear skew looks funny (well dishes without straight poles skew too) ;; so it does work, and there are resultant gains for one polarity or the other; because of the dishes design (taller than wide) or (wider than tall); which allow the design factors to "help" for certain channels, sats, or polarities!

 

[Titanium]

Do not be confused and think that the you can leave the feedhorn in the center of the parabola and change the pitch or yaw to pick-up other satellites. Changing the pitch or yaw only positions the opening at an angle that is not optimized for the reflected signals to enter the wave guide or feedhorn cavity. The feedhorn opening must be placed in the sweet spot where the reflected satellite signal converges. Satellite signals from different azimuths and elevations do not reflect to the same sweet spot. The second LNBF must be offset to the left/right and raised/lowered to place the feedhorn opening in the point of convergence to capture the reflected signal of a second satellite located at a second azimuth and elevation.

Side by side DBS Ku/C feedhorns only worked because the DBS signals are so strong that the KU feedhorn could be sitting outside of the convergence point and still gather enough signal to provide reception. The DBS KU feedhorn was capturing only part of the reflected signal as it was not exactly pointed at the same satellite position as the C-band feedhorn.

 

[richyrich]

Pitch and yaw are already used as the lnbf offset angle; accruing pitch and yaw as a place the sweetspot is. These are the same angles used to offset across the horizontal area's also using the dish to provide "many" sweet spots; the bigger the dish, the more sweet spots they actually have; or can be used. They are not any different than the already used sweet spot; centered at flat offset (this is center of dish V/center of dish H @20 degree's on most of today's ku dishes). the sweet spot is curved though, not flat (lnbf's waveguide entries draw a curve). 90 degree's turned the gstar dish; more area now in horizontal area. The lnbf is now way off to the side of the dish; aiming horizontally across the dish. Skew the lnbf back to correct position for satellite received (90 out to line up H/V because vert. is now still at top of dish). This dish is pointing 40 degree's off where it looks like it will work! And it does work, once you set the skew and aim (it looks so funny) the thing at some ungodly angle! It picks up the signal of any satellite you aim it at (even weak ones). And offset then is still in the sweet spot! Not to mention, it looks very funny, with a 90 degree offset pole, and the elevation is set using the pole and elevation measure of dish goes east/west. But the offset is STILL IN THE SWEETSPOT; AND YOU CAN FIND 7 -15 more sweetspots; if mounted in the exactly right place; and receive along an 80 degree horizontally mounted "curve" to receive all of them just fine (if the dish is big enough)! According to the workmans code. If it works; don't fix it! Just more than one sweetspot is not written, does not prove they do not exist as the 90 turning of a dish points out!

 

[richyrich]

The problems occur only when the angle asked for receives a shadow of the center of the dish, caused by another lnbf in the way of the center of the second focused lnb. So when you mount two flat or parallel to a curve, they are in a shadow of each other, instead of angled from each other along the sweetspot (the arc is a frown in the sky; the sweetspot drawn, is, a smile (many places) when looked at (what the lnbf's draw with their waceguides) on a dish!!!! It actually looks like a bubble, around the shape of the dish or curved opposite the arc when aiming the arc with the lnbf, and extends all the way to outside the dish diameter (when at offset) all the way to the center of the dish (another focal point). Hood nite, im going fishen and campin instead; it is time to gear up. Remind's me of how many lnbf's it takes to watch tv co mpared to how many lnbfs can be placed onto a dish for multi-sat reception, and where each pick-up the sweetspot of the dish; and each satellite is received with high quality; and ku band dishes too; what does it look like? Two lnbf's for 2 degree's are not parallel to each other, they are at an angle and spacing; and both receive from the middle of the dish their own "sweetspot"! This angle is the 2 degree's; how much the two faces of the lnbf's are angled "past each other" so no shadow shows to either lnbf; and they both aim at exactly the center of the dish; and the dish is set solidly in one direction.

 

[KE4EST]

!

I will try to remember that.

 

[richyrich]

Yeh, the picture is of a satellite dish that pics up all satellites at once; and doesn't ever move. It is quite powerful that way!

IM watchin Alaska. The dish looks like a rollercoaster of angles; and big, and ugly; whew, glad im goin fishin...

 

[jorgek]

Would an eliptical dish be better suited to multi lnb use rather than a standard FTA offset type?

 

[Titanium]

There is feeding the troll then there is making sure that satellite hobbyists trying to learn about the technology receive correct information.... Some pretty bizarre misinformation being put out there!

Regardless of what multiple repeating posts may claim, an offset or elliptical is simply a section of a parabola. Physics and geometry rules apply. The ratio of highth and width have no affect on signal polarity gains. A horizontal elliptical will not favor horizontal polarity reception. Surface area does not discriminately reflect select signal polarities.

It should be noted that horizontal elliptical designs tend to provide slightly better side lobe attenuation for rejection of adjacent satellite interference while vertical eliptical designs typically have nominally better ground noise rejection. This is only because the surface area favors either the horizontal or vertical planes.