Trouble with Ku Signals on 10ft Mesh Bud

[Captain Midnight]

Has anyone else had a bunch of trouble tuning Ku band on a 10ft Mesh? My mesh is Ku compliant and the dish is not badly damaged for being 30 years old... But it is frustrating.

Only reason I tried it is because my STAB H-H motor suddenly stopped working and I was curious about how Ku signals would come in on my BUD. I'm using a Chap Corotor with a good Norsat LNB. It just has been a chore to peak the Ku arc. I know now my 1.2m offset beats the BUD hands down.

My dish has a slight warp to it that I correct with turnbuckle tensioned paracords from top to bottom and west to east sides of the dish. But the strangest thing is the tension needed to peak the Ku band is different than the C band tension. I would think both bands would be peaked by the same tension, as it holding the dish in a more accurate parabola shape?

For example, my signal on 87w Newsource goes from 12dB down to 10.4dB after I have the dish tensioned for optimum C band performance.

Anyone have advice for fighting with this? I'm about ready to give up and try to find a fix for the STAB...

 

[mr3p]

I spent a lot time trying to add a Ku LNB to my 10' dish and was never happy with the results which were consistently poorer than my 39" Ku.

 

[Captain Midnight]

I spent a lot time trying to add a Ku LNB to my 10' dish and was never happy with the results which were consistently poorer than my 39" Ku.

I was hoping it wasn't just me. From what I have read, Ku is really sensitive to dish shape. Wish I had a solid dish instead.

 

[c-spand]

I have noticed that the Ku lnb needs to be moved in closer to the dish. In the past 5 years things have changed from dvb-s to dvb-s2 there has been a change to move the lnb closer into dish. Another thing is each satellite has it's own characteristic. One may be fine tuned but another Sat may be off. Difficult to find the perfect happy place. ugh

 

[Radioguy41]

The main factor is the size of the holes in the mesh. My 7.5' KTI mesh receives Ku just fine while a friends 10' RS mesh has never been very good at it. Rule of thumb, if a pencil fits through the holes they are too big.

 

[Comptech]

Dedicated Ku dish is your best bet, running on a c-band dish is a comprimize.

 

[Captain Midnight]

The main factor is the size of the holes in the mesh. My 7.5' KTI mesh receives Ku just fine while a friends 10' RS mesh has never been very good at it. Rule of thumb, if a pencil fits through the holes they are too big.

Mine is Ku compliant. Pencil lead fits thru. Not the whole pencil.

 

[arlo]

I have very good results with a sidecar ku lnbf on my 12' solid 'glass dish.
It's a button hook feed so I ended up aiming the feed offset from center as the button hook mount was killing signal. C band vs ku is about 6 degrees offset. No biggie really.
I had to figure out the rough position by holding the thing in my hand. Then bend up a mounting bracket to hang on the c band scalar. Works pretty slick.
But this made me curious. What if a guy were to grab an aluminized space blanket from wally world and try some light spray glue and form it to the mesh dish surface to see if signal got better. Just to see. Hmmmm.

 

[primestar31]

What if a guy were to grab an aluminized space blanket from wally world and try some light spray glue and form it to the mesh dish surface to see if signal got better. Just to see. Hmmmm.

Buy the thick aluminum foil instead. It's MUCH thicker than the stuff we typically use in the kitchen.

 

[LocutusOfBorg]

Large Ku antennas have a tighter beamwidth which makes tuning difficult. LNB feedpoint and dish shape is critical also. I once worked on commercial grade 6 meter prime focus solid antennas and it took the better part of a day to align them. Even the 3 meter backup antennas were tough to tune. For home systems I recommend the 1 meter antennas for Ku. But I've heard that the motors are hard to come by these days.

 

[Captain Midnight]

Buy the thick aluminum foil instead. It's MUCH thicker than the stuff we typically use in the kitchen.

I've thought about that too. The issue is getting a nice clean and ripple-free surface. Every imperfection will bounce signals improperly. I think I just need to rig one of my 1.2m fiberglass dishes to the polar mount my 7.5ft SAMI uses. The SAMI is not being used.

 

[N6BY]

The mesh size is not the only consideration for using a C band dish for KU band. The amount of deviation from a true parabola is much more critical for KU than C band because of the shorter KU wavelength. (about 1 inch vs. 4 inches for C band)

Your mesh dish probably uses panels, which only approximate a parabolic surface. What happens is that the signals reflected off of your dish panels to the KU feed travel different distances and may arrive partially out of phase, which tends to cancel out some of the signal.

 

[arlo]

I have very good results with a sidecar ku lnbf on my 12' solid 'glass dish.
It's a button hook feed so I ended up aiming the feed offset from center as the button hook mount was killing signal. C band vs ku is about 6 degrees offset. No biggie really.
I had to figure out the rough position by holding the thing in my hand. Then bend up a mounting bracket to hang on the c band scalar. Works pretty slick.
But this made me curious. What if a guy were to grab an aluminized space blanket from wally world and try some light spray glue and form it to the mesh dish surface to see if signal got better. Just to see. Hmmmm.

Just to expand on the space blanket thing. I came across a Wild Blue dish some years ago with the tria sub reflector. The water/depth and calculation thing didn't work when trying to figure out where to put an lnbf on a fabricated bracket. Took my space blanket and some spray starch and plastered it to the reflector. The sun and a piece of paper gave me the "spot" (literally) in a minute. The starch washed right off.
Yeah. Foil. I thought of that too. And the wrinkle free finish. How about a piece of aluminized window film? It heat shapes with a hair dryer and holds up pretty good.
Other than that, I don't know squat.

 

[wagonman76]

My Ku comes in excellent. Sometimes better than C. I never used any special tools to center the feed, just a tape measure. Some satellites I do have to bump it a click to optimize one or the other, but it still comes in. 9 times out of 10, any bumping of the dish is due to accumulated missed counts in the actuator, or snow weighing down the dish.

I have no idea what my mesh size is. When I bought the house, it had C only. I added Ku for 4DTV back in the day, and it just worked.

Now I can understand why a mesh dish is lacking. A solid dish is a true parabola for the full circle. A dish with fitted mesh panels (flat metal sheet) is only going to be a true parabola at the center of each mesh panel. Anything else is going to reflect back at a point off center. Since the Ku probe has a much smaller collection area, you’re only going to get a fraction of the signal. C band has a larger collection area, so it’s not as bad. And maybe the scalar rings help further. But I would think a mesh dish is also going to give less signal on C as well.

 

[pacificrim]

I'm late to this thread, but I get amazing Ku reception on my 10' KTI.
The factors I dealt with are: PLL Ku LNB in the dual polorotor, adjusting the LNBF in or out of the ring, skewing the polorotor and the final piece was the elevation actuator I put in 2 years ago. It also really helps that I have a pro meter - the Applied Instruments S2.
I found that my elevation/declination even out by a small bit was a giant factor in Ku. I don't adjust it anymore, though I can with a button press, I just found it was easy to peak it at both ends of the arc and figure out where the problem was in either elevation, declination, or a mix of both - without a lot of wrenching back and forth.

I attached a drinking straw to the back of the elevation actuator, then peaked one side of the arc and drew a black marker line where the straw lined up next to a bolt head. Then swung the dish to the opposite end of the arc, peaked that side and marked the straw. There was a noticable gap between the marked lines. I then adjusted the declination and swung it to the other side or to my due south and peaked with elevation, marked the straw - were the lines further or closer?? More declination and elevation adjustments and progressively, the lines on the straw got closer and closer until the same line was the peak for all positions.


My big dish exceeds my 1.2 offset for Ku since I did this.