C Band LNB Placement on 90cm (1 Viewer)

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LibertyNT

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Oct 18, 2016
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I'm wanting to experiment a bit before I put my BUD up. I have a geosatpro 90cm dish and a Titanium Satellite C-Band LNB. I also purchased a bracket to mount the LNB to my dish that came with a MASSIVE scaler.
The main question I have is what the focal distance needs to be when I mount the LNB, the LNB is numbered on the side for what I assume is to set distance to a fixed number.

The Satellite I need to hit is AMC-8 at 139W, I'm in North Texas if that makes much of a difference.

The second question is, would it be better to use the bigger scaler that came with the kit, or use the scaler supplied with the LNB?
 

RimaNTSS

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Mounting of any LNB (Ku, C or Ka) should be done in the way that Phase center of the LNB is co-located with antenna's Focal point. So, before you do experimenting you should know where are those points are located. Do you try to mount LNB for Prime-focus dish on to the offset dish?
 
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Titanium

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Install the 40mm mount that was provided with the dish and a KU LNBF. Aim and optimize for KU transponder on 99w. Make a template that sits on the center support arm that measures the angle of the LNBF face aimed into the dish, the distance from the reflector and the height to the center of the LNBF cap.

Remove the 40mm clamp and install the 65mm clamp to hold the C-band LNBF the the same height (to the center of the feedhorn throat), same distance and angle to the reflector. Once the C-band LNBF is installed in the clamp, adjust the skew and fore/aft (focal length) to optimize the signal reception. Next install a conical scalar to optimize the signal quality. Then adjust BOTH the LNBF and the conical scalar to optimize. Then adjust the conical scalar, then both... repeat until the best Signal Quality is obtained.

The FD ratio of the GSP90cm is .6, so it is off the scale on the LNBF. The flat scalar provided with the C1-PLL is for illumination a prime focus dish with FD of .3- .4. This scalar will over-illuminate a reflector with .6 FD, shooting past the sides and susceptible to terrestrial noise. Mounting a conical scalar designed for the higher FD, requires experimentation and optimization by observation.

Be advised, I wouldn't expect to receive many C-band transponders on any satellite. Maybe only the fat DVBS MPEG2 LESEA transponder on 99 W. Doubt any other transponders on any other satellite will provide reliable reception with a 90cm dish. Never aimed a mini or micro sized dish at 139w, but the SNR on the transponders don't look adequate to break above the noise threshold using a low gain 90cm reflector.
 
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LibertyNT

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Oct 18, 2016
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Almost sounds like the C-Band LNBF needs to be as far back as possible (If I'm picturing the LNBF correctly). I have a dedicated XDS sat receiver that should help things a bit, talking to cumulus they said Radio Disney tried to use the 90cm dishes with what they called disastrous results. (In that it WOULD lock but just about anything would knock it out). I currently have the supplied ku LNBF and bracket installed, I'll try to hit 99W. So far I've TRIED to hit Galaxy 19 at 97W with no luck. I'm extremely new to the sat world and most likely I'm just not adjusting the dish correctly.
Getting back to the basics of dish alignment, which side of the GeosatPro do I use for elevation? There are two labled sides "A" and "B". I'm assuming I'd aim using "A" but haven't been able to reach a satellite yet.

Thanks for all the help so far!
 

Titanium

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Assembly guides can be your friend!:D

The scale choice depends on how the through-bolt was installed. Assemble the dish by placing the through-bolt in the post clamp hole stamped "A" for aiming at satellite elevations less than 50 degrees and in hole stamped "B" for elevations greater than 50 degrees.
 

LibertyNT

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Oct 18, 2016
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The Bolt was installed through B since the satellites I need to hit are above 50. (Aside from AMC-8 which is at about 30 degrees for my location)
Admittedly I had a somewhat hard time following the Geosat instructions beyond initial assembly. Using the "B" side of elevation shoots the dish almost straight up in the air for 51 degree elevation. "A" side looks more correct but neither hits Galaxy 19.
 

LibertyNT

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Oct 18, 2016
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Ultimately the Geosat will be fixed to Galaxy 19, with the BUD aiming at AMC-8.
 

Titanium

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Your talking to the guy who wrote the guide... LOL! :)

The GSP90cm has an offset angle of 24.62 degrees, so the dish is actually looking at a satellite position that is 24.62 degrees higher than the face of the dish is aimed. If assembled using the "B" clamp hole, then the "B" scale is used. As long as the post is plum and level, the scale is accurate within a few degrees.
 
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LibertyNT

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Oct 18, 2016
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Good to know! I'll keep trying at it. A sat guy I talked to did say G19 was just about straight up. (Which is good since now I know I'm adjusting elevation correctly, plus using the "A" scale the feedhorn arm kept hitting the roof mount post.)

One a side note, I have been impressed so far with the build quality of the GeosatPro. Seems like it can take a beating and keep going.
On a kind of funny note, my C-Band bracket didn't come with the clamp screws. I'm assuming the ku screws will work, I haven't tried yet. I had no idea they all shared the same manufacturer!
 

Titanium

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In Northern Texas, the maximum elevation for the top of the arc is around 50-55 degrees. Far from being straight up! LOL!

For aiming at a satellite at 51 degrees elevation, I would use the clamp hole "A" and reference scale "A". Reading the scale uses the white marking on the edge visible through the elevation scale on the left side of the nut. If the center LNBF support arm is contacting the mount post, the mount may need to be re-positioned or add a few inches of vertical height with an extension pipe. Most muffler shops can make a 1 5/8" extension in a few minutes. Have gone to a muffler shop many times when I couldn't change the customer's post mount, but needed a few more inches for clearance.

BTW: Install the roof/wall J post (pole) with the "J" at the bottom for maximum vertical height clearance and the "J" at the top for maximum horizontal reach.
 

LibertyNT

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Oct 18, 2016
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Thank you for your help! I'll try swapping the mount back over to A and go from there, great tip for the pole!

I think if I just raised the dish slightly on the mount I should be good to go, think I could temporarily get away with bumping the dish up on the clamp and just using the bottom two bolt holes to tighten it down? At the moment the pole is fully in the clamp with the top and bottom bolt holes for tightening.

Learning a lot today!
 

Titanium

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It will be a PITA to aim and optimize the dish alignment with the clamp not firmly seated on top of the mast. I wouldn't want to do it! It will make a difficult situation and add to it...

Is the "J" end of the mast at the bottom already?
 

LibertyNT

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Oct 18, 2016
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J is now at the bottom and I flipped the bracket as suggested.
I suppose at this point we'll take it from the top, I cannot get 99W or 97W on ku.
 
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Titanium

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What LNBF brand and model? Does it provide the LO frequency?
What is your zip code?

Using a TV next to the dish with a small TV to see the Signal Quality meter reading?

What is the LNB type in the receiver????
What is the LNB LO frequency setting in the receiver?
What is the LNB Power setting 13/18 (or automatic) in the receiver?

On 97w use transponder Frequency:12152 / Polarity:Horizontal Symbol Rate: 20000 as this transponder is not duplicated on several satellites on either side of 97w.

Use www.dishpointer.com to determine the LNB skew rotation then set, the dish elevation and loosely set and the approximate compass reading to aim the dish and aim. Locate a landmark as far in the distance that lines up closely with this compass reading.

While watching the SIGNAL QUALITY meter reading, SLOWLY pan the dish East and West 15 degrees on each side of the target landmark. If no Signal Quality reading, increase and decrease the elevation setting in one degree increments and SLOWLY repeat the sweep on either side of the target landmark. Repeat until the SIGNAL quality is noted and optimized. Move the LNBF fore / aft and slightly twist the skew to optimize the Signal Quality reading.
 

LibertyNT

Thread Starter
Well-Known SatelliteGuys Member
Oct 18, 2016
26
18
Texoma
What LNBF brand and model? Does it provide the LO frequency?
What is your zip code?

Using a TV next to the dish with a small TV to see the Signal Quality meter reading?

What is the LNB type in the receiver????
What is the LNB LO frequency setting in the receiver?
What is the LNB Power setting 13/18 (or automatic) in the receiver?

On 97w use transponder Frequency:12152 / Polarity:Horizontal Symbol Rate: 20000 as this transponder is not duplicated on several satellites on either side of 97w.

Use www.dishpointer.com to determine the LNB skew rotation then set, the dish elevation and loosely set and the approximate compass reading to aim the dish and aim. Locate a landmark as far in the distance that lines up closely with this compass reading.

While watching the SIGNAL QUALITY meter reading, SLOWLY pan the dish East and West 15 degrees on each side of the target landmark. If no Signal Quality reading, increase and decrease the elevation setting in one degree increments and SLOWLY repeat the sweep on either side of the target landmark. Repeat until the SIGNAL quality is noted and optimized. Move the LNBF fore / aft and slightly twist the skew to optimize the Signal Quality reading.

Ku LNBF: GEOSATpro SL1PLL
LO: 10750MHz
Zip: 75418
Signal Quality: 0%
LNBF is powered on per the "Strength" Reading.
Reciever settings match the current LNB. Reciever is X2 M1HD. Power setting is "ON" which I take to be automatic as 13/18V and OFF are the only other options.

Thanks so much for your help so far. I'll try the sweep method.
Setting the reciever to that transponder the "strength" constantly jumps from 50% to 70%.

Edit: turning LNB power off changes nothing as far as the "strength" meter goes.
 

Titanium

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Is the Power setting of 13/18V a single item or is there a 13V and a 18V and OFF settings? If separate line items for ON, OFF, 13V and 18V, select ON. If 13/18V is a separate line item, select 13/18V.

Turning the LNB Power OFF should change the Signal Strength to 0 or nothing. Strength reading typically only means a powered LNB is connected to the LNB IN port. It does not indicate that the dish is aimed at a satellite or at the ground.

Is the TV out at the dish where you can see the SIGNAL QUALITY meter reading?
 

LibertyNT

Thread Starter
Well-Known SatelliteGuys Member
Oct 18, 2016
26
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Texoma
They are separate line items, I left it in the "On" setting. Thats what I fugured "strength" meant as I've seen others mention it that way. Turning the LNB power to "off" changes nothing, however disconnecting the coax does result in all 0's. (Well 12% strength actually, what a near useless meter)

The TV is behind 50 feet of coax in the radio studio, I have a small portable I can use at the dish.
 

Titanium

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The Signal Strength meter has no purpose on consumer STBs other than to confirm a working LNBF is attached. The Signal Quality Meter is the only meter that is used for verified signal acquisition and optimizing.

Aiming a dish without a TV (or a good, quality meter) beside the dish is not totally impossible, but it would be only by a stoke of luck that you would find the satellite... :eeek

Dont waste your time until you can see the Signal Quality meter reading as you SLOWLY adjust the dish.
 
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