Rusting satellite dish

[N_Cook]

No reception problems , even in heavy rain, but presumably will do some
time.
If the dish completely rusts over , so no longer smooth, but not
actually pitted with holes or distorted, would there bound to be
received signal loss associated with rust rather than paint?
What sort of paint over the front surface , when the rust is cleaned back ?
If actual rust holes , from thinned metal that does not survive rust
cleaning, then how to deal with that.?

 

[Tim R]

On Friday, March 25, 2016 at 12:00:00 PM UTC-4, Jeff Liebermann wrote:

Also, note that the color and surface finish of the dish is rather
important. The common gray color is designed to both reflect and
absorb a minimum amount of heat from the sun. If the dish were a
mirror finish, when the sun goes behind the satellite belt twice each
year, the reflected light would burn up the LNB. I've had it happen
on larger dishes. If the dish were painted flat black, it would

Hmm. OT maybe, but........ a little bit ago we needed to measure a large number of throws of Frisbee golf discs. I had one of those big reflective round traffic signs, about the size of a good size satellite disc. It was a No Entry One Way (but the international symbol, not words). That thing really reflects, my little LED headlamp will light it up two blocks away. The back of it is just gray sheet metal but the front, wow, that reflective paint is great stuff.

So the plan was have the kids throw from where the sign was set up, then go to where each disc lands and shoot back to the sign with my laser range finder.

Surprise. The range finder won't read off a reflective sign at all, at any distance. Turned the sign around and it read fine off the unpainted back. I hadn't expected that.

 

[whit3rd]

On Friday, March 25, 2016 at 5:35:51 AM UTC-7, N_Cook wrote:

No reception problems , even in heavy rain, but presumably will do some
time.
If the dish completely rusts over ...

Oh, there's a solution for that, from the world of architecture.
Plant ivy.
Seriously, there's very little effect unless the dish changes shape; the
Arecibo telescope doesn't look like a shiny-new dish, and it focuses
radio just fine. And a thin layer of paint won't keep the underlying metal
from blocking the passage of radio waves, so it'll still reflect if you decide
to apply some finish.

 

[Ralph Mowery]

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:nd3b52$q7b$1@dont-email.me...

No reception problems , even in heavy rain, but presumably will do some
time.
If the dish completely rusts over , so no longer smooth, but not actually
pitted with holes or distorted, would there bound to be received signal
loss associated with rust rather than paint?
What sort of paint over the front surface , when the rust is cleaned back
?
If actual rust holes , from thinned metal that does not survive rust
cleaning, then how to deal with that.?

The dish needs to be smooth or there will be some loss. If already rusted,
you should get a new dish. That is assuming you are using one of the small
units for Direct tv or Dish. The very high wavelength needs a smoother
surface than the older 10 foot size dishes.

The paint should be of the type that does not have conductive particals in
it.

 

[Jeff Liebermann]

On Fri, 25 Mar 2016 12:35:51 +0000, N_Cook <diverse@tcp.co.uk> wrote:

No reception problems , even in heavy rain, but presumably will do some
time.

Most of the 0.6m DBS reception problems I've seen are the result of
bad or unstable dish aiming. However, if you experience fades and
dropouts, the easiest fix is to just buy a bigger dish. Mine is 1.0m
diameter:
<http://802.11junk.com/jeffl/pics/DBS/slides/101b.html>

If the dish completely rusts over , so no longer smooth, but not
actually pitted with holes or distorted, would there bound to be
received signal loss associated with rust rather than paint?

Yes. Ferrite (iron oxide) is an RF absorber. If you want to turn
your dish into a radar invisible stealth aircraft simulation, just let
it rust a little. To be fair, the layer of rust has to be fairly
thick in order to have an effect, so you might be able to get away
with it.

>What sort of paint over the front surface , when the rust is cleaned back ?

Paint that contains no carbon, graphite, iron oxide, or any other
additive that might be considered an RF absorber.

Or, you could just let your imagination run wild:
<https://www.google.com/search?q=paint+satellite+dish&tbm=isch>

If actual rust holes , from thinned metal that does not survive rust
cleaning, then how to deal with that.?

I'm all for repairing things, even if they're not worthy of the
effort. I would use automotive body putty to fill the hole, and a
piece of aluminum foil to replace the missing part of the reflector.
Getting the foil to simulate a parabolic shape will be difficult, but
not impossible. I suggest a wooden form.

Also, note that the color and surface finish of the dish is rather
important. The common gray color is designed to both reflect and
absorb a minimum amount of heat from the sun. If the dish were a
mirror finish, when the sun goes behind the satellite belt twice each
year, the reflected light would burn up the LNB. I've had it happen
on larger dishes. If the dish were painted flat black, it would
absorb enough heat to distort and temporarily loose shape. I don't
know how Dish Networks gets away with black reflectors. The surface
finish is a compromise between smooth for maximum gain, and matt for
minimum light reflection. Whatever you do, don't paint it with glossy
paint or you will cook the LNB.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Andy Burns]

Ralph Mowery wrote:

"N_Cook" <diverse@tcp.co.uk> wrote:

If actual rust holes, from thinned metal that does not survive rust
cleaning, then how to deal with that.?

Is it a solid dish or a mesh one? I don't think I'd be bothered to
repair a dish unless it's something special, buy a new one for ÂŁ20-30.

> assuming you are using one of the small units for Direct tv or Dish.

From the email address, I'd say it's more likely for Astra 28.2E
satellites.

 

[MJC]

In article <328070ca-dfe1-4038-ab54-edaa1a93171f@googlegroups.com>,
timothy42b@aol.com says...

Surprise. The range finder won't read off a reflective sign at all,
at any distance. Turned the sign around and it read fine off the
unpainted back. I hadn't expected that.

That's a surprise to me too. I thought the laser range-finding to the
Moon was done using a retro-reflector placed there specially by
visitors. But maybe they did not use a road-sign...

Mike.

 

[Bob F]

Andy Burns wrote:

Ralph Mowery wrote:

"N_Cook" <diverse@tcp.co.uk> wrote:

If actual rust holes, from thinned metal that does not survive rust
cleaning, then how to deal with that.?

Is it a solid dish or a mesh one? I don't think I'd be bothered to
repair a dish unless it's something special, buy a new one for Ł20-30.

Or pick up an unwanted used one via freecycle or craigslist.