Circular feed improvements!!!

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gpcramins

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Jan 4, 2006
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Hello folks,

As some of you who have seen my posts may know, I have been trying to improve my reception of NSS-5 (C band) with a 1.8 meter dish receiving a left hand circular feed in Guam. I hope my trial and error method of improving the signal strength may help others here who are trying to receive similar polarization from this sat and others. If this is commond knowledge, forgive my post but I could not find any info through my searches of the forums... I first tried to receive circular polarization using one of the fiberglass plates normally supplied with an LNBF. My LNBF was a 22 K PBI Turbo 1200, with a stability of 0.5khz. There were no slots so I simply hot glued the plate to the feedhorn cover, adjusted it and tried reception. I could not get anything above a signal quality of 35. I tried another LNBF (Pauxis model, 17 K, 2 mhz stability (!!!!) which did not have a plate but my wife's old cutting board supplied a teflon plate (teflon has great dielectric qualities) which took me well over an hour to sand to size. I still could not get anything over 38-39 for signal quality on my reciever (a cheap Chinese brand named Chieta, I do not recommend them...).

After a few beers (the neurons began operating properly), I tried glueing the fiberglass plate to the feedhorn cover (external side), thus giving me two plates, one internal, one external. I could not believe the results, signal quality over 45, excellent picture and stability (no pixelation, etc.). I am waiting for the proper plate (internal) from the local distributer and may try additional methods to improve the signal further, which I believe can be accomplished with a larger plate affixed to the front of the feedhorn.

The best part was I accomplished this with an older LNBF, which has poor stability (in my opinion, and I am a newbie so go ahead and hammer away...) so if you have a PLL unit, you could probably get much better results than I did. Needless to say, the wife is happy, which means the nagging will temporarily cease. If you have a smaller dish and are having a hell of a time receiving circular feed, I hope my advice helps.

Garry
 

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great job!

Great job on your dielectric plate, you will fit in with us just fine, we can always use more backyard engineering skills in this community.

I am using a somewhat homemade c/ku lnbf combo on my 7.5' MESH sami dish.

I used an astrotel c-band lnbf, cut a hole in the rear end of it with a hole saw, used epoxy putty and glued a ku lnbf in the rear of the c-band lnbf.

I was careful to align the probes so the skew would be the same.

It works great and i do not have to use a servo motor for polarity control.

This simplifies my setup because i can use my free to air receiver independently from my 4dtv receiver. If i had a servo motor i would have to use the motorola 4dtv to change from horizontal to vertical polarity.

I used a set of high frequency power passing tru spec splitters and voila!!

works like a charm.
 
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