lnbf test

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dxuall1

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Dec 4, 2007
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:confused: how can i check/test to see if is working one c-band lnbf that a friend of mine gave me today???? info available precision (casing brand) lnb:california amplifier mag-90 hemt low noise block converter part #31572 gain:65db typ. input:3.7-4.2 ghz noise:30k output:950-1450 mhz s/n4100146788 the lnb looks new the "casing" looks a little bit corroted with paint pealing off. need help. will this thing work with my 1.2 meter dish????
 
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qwert1515

qwert1515

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Sep 26, 2005
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The easiest way to test an LNB it to try it! ;) The LNB should give you something on the 1.2 Meter Dish.
 
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dxuall1

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Dec 4, 2007
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mission,tx
do i put on the dish the whole blue "casing" or just the lnb alone? do i only conect the coax cable right? how about the polarity? how can i know what polarity is right now? i cant use the servo motor. I just want to use it like a ku lnb. but as c-band. i'll probably find a strong transponder and find a specific channel and polarity and test it. what do you guys think will it work or not????
 
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qwert1515

qwert1515

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I didn't realize that it has a servo motor, this link might help: LNB/Feedhorn Assembly Also look at the "International Feed Diagram" on that page.

If you can figure out (Maybe by experimenting) how to skew it you might be able to use it for one polarity at a time. You also need to figure out how to mount the larger LNB.
 
turbosat

turbosat

SatelliteGuys Master
Dec 26, 2006
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Oneonta,AL
What kind of feedhorn is it attached to? If it's one that has a bolt/set screw on the feedhorn body, you can loosen that to manually "skew" the lnb if you have no polarotor voltage.
Now, as to how a prime-focus feedhorn/lnb will work on on offset dish...you may have to rig up some braces to hold it at the proper focal distance and aim the dish like a big dish.
 
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dxuall1

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SatelliteGuys Family
Dec 4, 2007
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yessss the feedhorn/lnb worked. I had no problem with the focal point. just put it where the old prime * lnb was point it straight to the center of the dish, moved it out as far as i could enter one strong transponder in my box played around with it and bingo quality 27-40. my experiment was about to see if my 1.2 meter dish will work for c-band and it did. on satmex 6 got like 6-8 channels and on satmex 5 i got like 9-14 channels and i bet there's several other channels that i can receive i think i'am going to buy the c/ku band lnb. I had to manualy move the polarity. the c/ku band lnb changes polarity by itself????
 
Anole

Anole

SatelliteGuys Master
Sep 22, 2005
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Lnbs like the GeoSatPro C/Ku unit and BSC-621, are voltage controlled.
Linuxman did a good discussion of aligning his GeoSat late last year on a 10' ? dish.
He got both bands pretty well.
 
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dxuall1

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SatelliteGuys Family
Dec 4, 2007
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mission,tx
what is voltage controlled?????? is it more dificult to set??? It will receive one band/polarity better than the otherone????
 
Anole

Anole

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Sep 22, 2005
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L.A., Calif.
Read that link QWERT posted above for more info on the more traditional BUD LNB, scaler ring, and servo motor for polarity.
The BUDs of 20 years ago used one expensive LNB, on one polarity, and a servo motor to change that polarity from V to H.
That technology is still fine today, as it is well proven and reliable.

Voltage-controlled LNBs use 12/18 volts to change between vertical and horizontal polarity.
The bulk of modern FTA receivers only have the ability to control polarity through the voltage fed to the LNB.
For examples of that sort of hardware, read the link I posted above for Linuxman aligning his GeoSat on C & Ku.

There is a lot of fundamental technology to learn, but once you have a grip on it, mostly it's pretty simple.
 
qwert1515

qwert1515

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Sep 26, 2005
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Los Angeles CA
Voltage controlled means that the receiver sends out 13 Volts for the Vertical polarity and 18 Volts for the Horizontal polarity.

EDIT - Anole beat me :)
 
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