new 1.2 meter dish and 12 footer

[arlo]

Great! When I saw your setup and you mentioned that you got more sig with the conical scalar off, my first thought was "under illumination".
As far back as you could get the scalar you were blocking some of the outer rim of the dish.
If I had a box of scalars I'd try to cut off some of the front or back then see where signal was optimal w/o getting adjacent sat tp interference.
That scalar would probably start to shine on a 6 footer on up. But hey, what do I know...

 

[Titanium]

The scalar design is based on the FD ratio of a reflector and not the reflector's diameter.

A standard flat scalar which is included with C-band LNBFs is designed for .3 - .4 FD ratio reflectors and a typical conical scalar is for FD .5 - .6. FD ratio reflectors.

That scalar would probably start to shine on a 6 footer on up.

 

[arlo]

The scalar design is based on the FD ratio of a reflector and not the reflector's diameter.

A standard flat scalar which is included with C-band LNBFs is designed for .3 - .4 FD ratio reflectors and a typical conical scalar is for FD .5 - .6. FD ratio reflectors.

Math and engineering aside. Johnny got better signal with no scalar. And less with the conical. But better with a flat scalar.
Just like when I started my C Band rant some time ago. I did all of the calcs. Scalar right where it "should have" been.
LNB tweaked to the you-know-what. The dish was very sensitive to axis adjustments. If you remember. Putting a chunk of aluminum inside of the dish rim until signal started to diminish showed that the mathematically correct scalar location was in fact under illuminating the dish.
Lucky I have a button hook feed because I ended up moving the scalar back quite a bit (in dish terms) from where the number dot said it should be.
Johnny could fashion a bracket that would locate the LNBF mounting bracket further back on the waveguide and then try moving the conical scalar back away from the dish. If you look at his photos it is as far as it can go right now. Cut it or move it. Any port in a storm.
Correct? Or do I need a little more shortwave Jesus?

 

[Titanium]

As I always state, calculations are a starting point.

Yes, he likely could modify hardware to futher optimize for reception of specific transponders on specific satellites. Optimizing for specific signal combinations will reshape beam patterns, under/over illumination and choke effect. Perfect if installing a fixed, but not optimal for a motorized dish.

His feedhorn mounting position optimization doesn't match any of my previous minibud testing. My optimized feed and scalar positions are shown in the CS1 product photos and approx the same as Comfortably Numb's photos. I have also found that no scalar or a flat scalar would often provide a higher SNR as long as terrestrial interference is minimized. I posted similar minibud findings on this forum back in 2010/11.

It makes no sense to move the feedhorn out of the original signal convergence sweet spot using the supplied KU LNBF. Wonder if he checked the reflector for warping or shipping damage? String test? A warped dish would definately affect the convergence point and be optimized with a fore/aft feed placement shift.

Shortwave Jesus? Huh?

 

[LocutusOfBorg]

Looks like part of my problem is that Univision is 7/8 FEC now. I don't know if I can get it any better than 6.2 dB C/N but it seems that it comes in better when the temperature gets below 80 degrees. Anyway, the dish doesn't look warped but I'll double check with a string test.

 

[LocutusOfBorg]

If I did the string test correctly, then I have a warped dish. I got about a quarter inch gap where the strings cross. You really can't tell from the photos - I just couldn't get a good angle that would show it.

 

[Titanium]

Should be laying flat where the strings cross. Check several angles before uninstalling to fix.

The clamshell or warp may not follow the H or V axis. Laying g the reflector face down on a perfectly flat surface will help identify any raised reflector edge. Simple to correct a slight warp then reinstall.

 

[LocutusOfBorg]

Should be laying flat where the strings cross. Check several angles before uninstalling to fix.

Since there's already a gap I'm wondering why you are recommending doing additional tests from different angles.

The clamshell or warp may not follow the H or V axis. Laying the reflector face down on a perfectly flat surface will help identify any raised reflector edge. Simple to correct a slight warp then reinstall.

 

[Titanium]

In order to understand if or how to correct, you need to identify if one side has been bent, if the reflector is clam shelled or the exact angle of the warp.

Most mild warping can be easily corrected, then the reflector remounted.

 

[LocutusOfBorg]

I did another string test that's rotated 45 degrees from my first test and I didn't find any gaps. The strings touched in the middle. See photo of the test along with additional photos of the installation. Kind of strange using such a huge actuator with such a small dish.

 

[Titanium]

So you determined that the warp or bend is on the original axis.

Is the warp caused by the mount?

 

[primestar31]

Johnny, if you can do it, please get us some shots straight from the BACK of the dish, showing the way you have the two pieces of threaded rod connected to the dish & mount. IF those two rods aren't exactly the same length, they may be causing a slight torquing the dishes natural shape.

p.s. IF you attempt to make adjustments to the various mounting brackets or pieces to try to get the proper shape back, only do it when you have the mount pointed True South. It'll make it easier to see changes to it as it should be naturally balanced in that position.

 

[LocutusOfBorg]

Johnny, if you can do it, please get us some shots straight from the BACK of the dish, showing the way you have the two pieces of threaded rod connected to the dish & mount. IF those two rods aren't exactly the same length, they may be causing a slight torquing the dishes natural shape.

There's only one adjustment rod that came with the dish. It was called a fine tuning rod in the instructions. The rod is L shaped. I believe there's an image of the rod in the manuals section of the forum and how it connects to the dish. Anyway, I had to fabricate a longer rod to make it easier to do that adjustment. I suppose that the dish can be aligned without it.

 

[a33]

It could also be that the LNB-arm and side-arms combination pulls the dish in a warp.
That's why some people also mount 'side'-arms at the back of the dish.

Anyhow, it's up to Mr. Nobody to do the in situ analysis, I guess.

Greetz,
A33

 

[LocutusOfBorg]

Johnny, if you can do it, please get us some shots straight from the BACK of the dish, showing the way you have the two pieces of threaded rod connected to the dish & mount. IF those two rods aren't exactly the same length, they may be causing a slight torquing the dishes natural shape.

See attached photos.

 

[LocutusOfBorg]

Birdseye view.

 

[LocutusOfBorg]

I got the string test down to an eighth inch gap. Not sure if I want to flex the dish any further. I still lose a half dB C/N with the conical scaler so I left the flat scaler in place. I'm getting 7.5 dB C/N on 4000H on 99W and 9.0 dB for 3760V on 97W and 6 dB for 3744V on 101W.

 

[primestar31]

Thanks for the pics, they show your setup much better than what I thought I noticed. I don't see anything obvious from your mount, that seems like it could be the reason the dish might be slightly warped.

I DO notice that your lnbf is a older Titanium C1W-PLL version with the extended lower range. I think that because of the smaller dish (compared to a full size c-band dish) you might benefit in swapping that out for the much newer version C1-PLL, with the new filters.

 

[LocutusOfBorg]

Thanks for the pics, they show your setup much better than what I thought I noticed. I don't see anything obvious from your mount, that seems like it could be the reason the dish might be slightly warped.

I DO notice that your lnbf is a older Titanium C1W-PLL version with the extended lower range. I think that because of the smaller dish (compared to a full size c-band dish) you might benefit in swapping that out for the much newer version C1-PLL, with the new filters.

I was wondering if the one with the 3.7-4.2 GHz range might help. Only one way to find out. I have one on the 12 foot BUD but I don't think it improved reception on it.

 

[N6BY]

About warped GeosatPro 1.2 meter dishes:

I am on my third dish (first two got bent). It took me that long to realize NOT to adjust the dish with my hands on the outer edges, especially if the dish is fairly tight on the pole. Instead, I now adjust with my hands near the center of the dish where it won't bend it. Lesson learned.

Fortunately it is only a 10 minute drive from my house to SatelliteAV so I didn't have to pay shipping when I bought replacements.