I'm trying to build a PA3FYM dual band feed and am confused about the LNB part of it, what type of LNB should I use and how should I connect the LNB to the waveguide.
Some questions for PA3FYM feed
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A simple approach is remove the enclosure from the lnb , cut off the feedhorn. Here is a picture of one of my first antennas. The copper pipe is way too long in this picture, but it worked. After some test, i modified the enclosure to fit again. An even simpler approach is to leave the enclosure on and drill a hole in the front cap of the lnb, just with the outer diameter of the copper pipe. Then stick the pipe through that hole and gently push it into the horn. The lnb you use is not critical, as long as it is a lnb with a xo . There are a lot of examples floating around on this reflector.
73, Martin
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A simple approach is remove the enclosure from the lnb , cut off the feedhorn. Here is a picture of one of my first antennas. The copper pipe is way too long in this picture, but it worked. After some test, i modified the enclosure to fit again. An even simpler approach is to leave the enclosure on and drill a hole in the front cap of the lnb, just with the outer diameter of the copper pipe. Then stick the pipe through that hole and gently push it into the horn. The lnb you use is not critical, as long as it is a lnb with a xo . There are a lot of examples floating around on this reflector.
73, Martin
Thank you very much, is the length of the waveguide actually a non-essential item? If it is then I understand and I will push on.
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Thank you very much, is the length of the waveguide actually a non-essential item? If it is then I understand and I will push on.
Not sure about that. A longer pipe will probably introduce some attenuation, but i don't know the numbers.
I have a fairly big dish and i am in Europe, with plenty of signal from the satellite, Elevation about 31 deg. I suspect your elevation is very low, so every fraction of dB may count.
But there are some guys here in the forum who managed to operate from low elevation places, maybe one of them has better answers.
73, Martin
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Coaxial cable is a form of waveguide, I doubt a few inches on a straight guide of that diameter will attenuate too much, but shorter will of course be better, mechanical constraints aside.
I made a Teflon adapter up to mount my unmolested LNB, the idea being I can also insert a long length of 15mm tube inside the adapter and verify it is pointing to the precise centre of the dish, and measure the focal distance precisely.
