Rusty Satellite Dish

[B@rrels]

Does a rusty/discoloured dish affect your signal strength or quality?Does it need to be white and reflective to operate efficiently?I have thought of painting it but if it doesn't make a difference I wont bother.

Thanks Guys

 

[HapticSimian]

I'll take a flyer here and say that I cannot foresee that colour would make a whit of difference. You're dealing with waves far outside the visible spectrum, and those big-ass mesh dishes are often black.

I can however imagine that the shape and texture of the dish could have a marked effect. If it's rusted badly enough to have bubbled the surface, or it's warped out of shape, a new one would probably alleviate any signal issues. Also, a small difference in size - say 80cm compared to 90cm - will make a big difference.

 

[B@rrels]

I'll take a flyer here and say that I cannot foresee that colour would make a whit of difference. You're dealing with waves far outside the visible spectrum, and those big-ass mesh dishes are often black.

I can however imagine that the shape and texture of the dish could have a marked effect. If it's rusted badly enough to have bubbled the surface, or it's warped out of shape, a new one would probably alleviate any signal issues. Also, a small difference in size - say 80cm compared to 90cm - will make a big difference.

Thanks for the reply.It is not rusted as such,just a surface rust colour.

 

[Quantum Theory]

The signal actually goes through the paint and reflects of the metal. In composite (fibreglass) dishes, there is a metal mesh inside... Like enigma243 said, if the shape is affected, bin it.

 

[upup]

I painted a very rusted one. It still works. In case you wonder with what, normal paint.

 

[Gambit]

I have been told in the past by knowledgeable people that you should not paint a dish with glossy paint.

 

[Tacet]

I'm not sure about the paint part, we don't ever paint our dishes, but those in my domain is normally covered by a radome cover.

As for rust - if the surface isn't smooth it can affect your signal. Think of your dish as a mirror which reflects all the light back to the horn feed. If a mirror isn't smooth, the light scatters and the reflection becomes blurry. Same with microwave - if the dish isn't smooth, the microwave scatters. Non linearities can do funny things to a signal.

If your dish is starting to rust, I'd recommend that you do paint it to prevent further rust. I wouldn't apply too much paint - as liquids can also attenuate a signal (make it weaker).

If you experience signal issues, make sure that your dish is properly panned (looking in the right direction) before going to buy a new dish. I don't know what mechanism your system will use, but most systems provide some means of getting the signal strength without having to watch on the TV. You'd normally make the dish look a bit to the left of where you think the satellite is, and then move it to the right. The signal should increase as you get closer to the right point, and then start decreasing as you move past. Once that happens, just go back to the left a bit. Repeat the process for the vertical. Always pan horizontal and vertical separately.

 

[AstroTurf]

Just use a can of appliance white or matt white if you want to paint it.

 

[zoopy3]

As for rust - if the surface isn't smooth it can affect your signal. Think of your dish as a mirror which reflects all the light back to the horn feed. If a mirror isn't smooth, the light scatters and the reflection becomes blurry. Same with microwave - if the dish isn't smooth, the microwave scatters. Non linearities can do funny things to a signal.

I doubt dish surface makes difference to signal because I've seen dish's made from all different materials like fibre glass, wire mesh, etc. if that's the case with a dish with a mesh surface, the surface will be rough and signal would be bouncing off it all over the place. In Durban here I see some dishes that has surface rust and works fine. To make the dish neat I would coat with a good heat resistant paint of any colour.

 

[Tacet]

... if that's the case with a dish with a mesh surface, the surface will be rough and signal would be bouncing off it all over the place.

That depends on the wavelength of the signal. Rule of thumb is that for a mesh, the holes need to be smaller 1/10 of the wavelength of the wave. To use another analogy - you can bounce a tennis ball on a grid if the holes are small enough, but if the holes are too large the ball will either get stuck or will fall through.

The problem with rust is that you don't know to what level it distorts the dish surface. "Rust" can mean discolouring, as is the case here, or advanced rust where there are large holes in the dish. Depending on how much rust there is it might or might not cause signal degradation.

 

[upup]

zoopy3,
Rather get a real installer, and buy a plastic dish.
Only touch your remote and not the dish.
You get antenna's call gridpack antenna's, http://www.zcg.com.au/grid-pack-antenna-mgp-6850n.htm
a small bird can fly trough it, but like Tacet says, its the wavelength that matters.
I got a 1meter dstv dish, was a pain to tune, very sensitive

 

[Tacet]

... very sensitive

I haven't panned a DSTV dish yet, but I can imagine that it will be very sensitive. That satellite is very far away, so a very small angular deviation will make a very large difference in space.

 

[Quantum Theory]

I haven't panned a DSTV dish yet, but I can imagine that it will be very sensitive. That satellite is very far away, so a very small angular deviation will make a very large difference in space.

Also, the bigger the dish, the smaller the aperture...

 

[Tacet]

Also, the bigger the dish, the smaller the aperture...

Yep, though we normally speak about beamwidth rather than aperture. A larger dish can easily half the beamwidth, making panning that much more difficult.

 

[AdrianR]

You don't need to move the dish. If it's picking up a signal still in the same place it was before, why move it? It's only rusted.

Mesh dishes are another thing all together. For DStv (10-12GHz frequencies) a solid dish is needed. Black mesh dishes are used for C-band (a much lower frequency 3-4GHz).

Anything on the surface (paint, rust, whatever) won't make a difference as long as it's smooth.

The only time rust will do anything is when it makes holes in the dish/pieces of it fall out, or large knobs/bubbles.

 

[Quantum Theory]

6 years...

 

[bwana]

Anything on the surface (paint, rust, whatever) won't make a difference as long as it's smooth.

The only time rust will do anything is when it makes holes in the dish/pieces of it fall out, or large knobs/bubbles.

Since you elected to resurrect this thread to impart wisdom what can you recommend wrt mine?

 

[Bryn]

A new dish is R400. Just replace the damn thing.

(Not bwana - I'm assuming he's trolling )