What attenuates the signal coming to LNBF

[polgyver]

Some dry items when put in front of LNBF do not impede reception of satellite signal.
Of course, metals, even as thinniest foil, will cut off the signal completely.
I was curious about water in its different forms : now I see that thick block of ice
does not impede reception.
But water in its liquid state - even as a thin layer - does block signal.
Annotated photos follow :

 

[LocutusOfBorg]

Snow does a good job of attenuating the signal also. I've never heard of ice never attenuating C or Ku signals. When I worked in the satellite industry they used heat blankets or forced air systems to keep snow and ice off the dish.

 

[a33]

Brilliant testing, polgyver !

I'm amazed about the plywood. Good to know, for people that cannot have a dish "in sight" on their balcony...

I once had a dish behind a window. Worked OK, but when it rained and a layer of water was on the window, reception was bad.
Of course, this was a window without metallic layer on the glas.

Greetz,
A33

 

[lost_mesa]

Very interesting polgyver. Thanks for posting your tests.

Snow in my C Band dish doesn't attenuate the signal much. But once it starts to melt and turns to slush, the signal drops way down.

I once read in Coop's Satellite Digest about a guy who had a C Band dish in his garage (wooden structure). I was skeptical, so stuck a piece of 2x4 in front of the feed. It didn't make much difference. Then I tried another piece of 2x4 that had been sitting in a puddle of water. It completely blocked the signal.

At one point in my life I had a 4 ft. Ku Band dish in my apartment living room. Pointed out the window to pick up NBC on K2 (or was it K1?)

My current home has metal in the window glass. Completely blocks XM radio and badly attenuates UHF TV. Both signals go through the walls pretty well.

 

[907TECH]

We service a large number of commercial systems in Alaska most have waveguide for the transmitters. We frequently see problems when spring rolls around and frost or ice in the waveguides starts to thaw during the day. They work fine while frozen but if any water is there, bye bye signal.

 

[LocutusOfBorg]

We service a large number of commercial systems in Alaska most have waveguide for the transmitters. We frequently see problems when spring rolls around and frost or ice in the waveguides starts to thaw during the day. They work fine while frozen but if any water is there, bye bye signal.

That's why they're suppose to be pressurized with dehydrators.

 

[907TECH]

That's why they're suppose to be pressurized with dehydrators.

And they are, but Alaska is a harsh place and things happen to cause leaks. Winter repairs are sometimes out of the question.

 

[polgyver]

Today I continued with trying other items as signal obstacles.
Wire mesh, thin or thick, has no practical value for us, satellite hobbyists, but for curiosity I tried them both. Thin plywood or non-transparent plastic might be useful for concealing a dish.
Cheers, polgyver.
Pictures follow:

 

[LocutusOfBorg]

And they are, but Alaska is a harsh place and things happen to cause leaks. Winter repairs are sometimes out of the question.

I hear ya. We had a lot less problems when we replaced rectangular waveguide sections with continuous runs of elliptical waveguide.

 

[polgyver]

I haven't tried yet to upload a short movie to our Forum, but will try now:
the title might be "How to wipe out satellite reception with Windex"

 

[polgyver]

Ooops... I tried to download a 31 sec. movie from my folder, same way as I did the pictures, but what I got is just a first picture of the movie...
It did not work...
Like Benny Hill used to say : "Learning all the time"...
cheers,
polgyver

 

[ReggieA]

What about regular (tarpaper) roofing shingles? Could I put a dish in the attic, and "see" through the roof?

 

[Cham]

Great use of covid isolation time there polgyver!
Didn't someone used to sell a fiberglass rock fixture to cover/hide a ground mounted DSS dish?
Might try different paint types on that thin plywood too, some might be more or less RF conductive.
People put TV antennae in the attic and they seem to work. Sat dish might as well as long as there are no nails, metal flashing, etc in the way. Wonder how an adobe roof compares to shingles?
Great topic!

 

[LocutusOfBorg]

What about regular (tarpaper) roofing shingles? Could I put a dish in the attic, and "see" through the roof?

I'm not sure about tar but a snow covered roof probably would wipe out the signal - especially Ku frequencies. But I have heard of snow melting systems for the roof.

 

[LocutusOfBorg]

Great use of covid isolation time there polgyver!
Didn't someone used to sell a fiberglass rock fixture to cover/hide a ground mounted DSS dish?
Might try different paint types on that thin plywood too, some might be more or less RF conductive.
People put TV antennae in the attic and they seem to work. Sat dish might as well as long as there are no nails, metal flashing, etc in the way. Wonder how an adobe roof compares to shingles?
Great topic!

I suppose there have been studies done but I haven't found any.