Primestar LNB adjustment screw??

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Techfizzle

Techfizzle

Thread Starter
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Apr 18, 2008
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I was bored so i cracked open a old primestar LNB, the small pop-can one, not the flat one. On the feedhorn neck, on the outside, there is a screw, but it doesnt hold anything, it threads threw to the inside of the feedhorn neck (the inside part on the opposite end of the lnb conenctors) You can see it if you look inside without taking one apart. I am wondering what this adjusts?
 
wizard101

wizard101

Well-Known SatelliteGuys Member
Sep 11, 2007
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This screw is likely a tuning screw used to improve the match of the feed horn to the input of the LNA. It could also be used to tune the magnetic/electric field to be orthogonal. At any rate if you adjust it, there is virtually no chance you will be able to put it back in the same position.
 
B.J.

B.J.

SatelliteGuys Pro
Oct 15, 2008
2,029
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Western Maine
I took apart an old LNB (not lnbf) once, and it had a screw that pushed against a small white teflon or ceramic cylinder. Being curious I asked a question similar to the above in another forum, and I learned that this was a mechanism to adjust the DRO oscillator, via variable capacitance. Having worked with piezoelectric crystals, I thought that perhaps it might have been a pressure/deformation effect, but I was told that it was not. Supposedly it changes the LO freq by relatively small amounts.
I'm not sure if the screw described above has a similar function, but it might.
 
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