Primary dish 10 m from home, secondary dish in the room

[polgyver]

The idea is to use slightly concave surface for preliminary increase of signal strength and sending it as a converging beam through the window and finally receive program using miniature secondary dish.
I spent many months trying reception with small, 8" secondary dish, but was not successful.
Finally, got it working with trimmed Shaw dish.
10 annotated photos follow :

 

[FTA4PA]

The idea is to use slightly concave surface for preliminary increase of signal strength and sending it as a converging beam through the window and finally receive program using miniature secondary dish.
I spent many months trying reception with small, 8" secondary dish, but was not successful.
Finally, got it working with trimmed Shaw dish.
10 annotated photos follow :

All I can say is WOW! You attempt things that most would never even think of trying and usually succeed as well. Love all of your work, especially this experiment! Thanks for sharing and hats off to you!

 

[polgyver]

From the beginning I was aware of 2 flaws in this idea:
1. A mirror with an underpressure will take shape of catenoid, not paraboloid
(some sources on Internet claim the shape would be part of a sphere, but
I doubt it)
2. The reception and following reflection of signal will be off-axis therefore
the focal cloud will be distorted with so-called Coma
Since the bending of the mirror surface was rather small, I expected that
the deviation from paraboloid of rotation would be acceptable.

The ratio of mirror surface to its focal spot (6") - for Sun light- is close to 32,
so, for protection from possible burning, I covered the mirror with painter's
masking tape, leaving 23 small rectangles which were enough to see what's going on when vacuuming the space behind mirror.
As there was small leak between mirror and board, I had to use a microswitch and lever on the back of the board to control the mini-vacuum pump.
This arrangement allows for adjusting effective Focal Length of the primary mirror.
I made a small (8") secondary reflector with focal length = 7", hoping that
it can further condense primary focal cloud(6") to feed the LNBF, but found out that it did not work.
This system is not easy to set up, but might work for someone who does not want visible dish on the house. It might work in some countries where dishes are prohibited (I heard that some people used garbage lids or similar objects to watch prohibited programs).
There are 7 annotated photos, below:

 

[Cham]

Nice work! Yes would be a decent system for hiding from public etc if you can get the geometery right for the desirable satellite. Interesting getting the long F/D by pulling a vacuum behind the primary mirror, whatever works. Guess if you got a really good seal you could vary the F/D by controlling the vacuum. Eventualiy you wouldn't need the secondary dish?
Once you get this working, you'll have to set it up as a movable system that always projects to the same point... I can feel the headache coming on already!

 

[polgyver]

Nice work! Yes would be a decent system for hiding from public etc if you can get the geometery right for the desirable satellite. Interesting getting the long F/D by pulling a vacuum behind the primary mirror, whatever works. Guess if you got a really good seal you could vary the F/D by controlling the vacuum. Eventualiy you wouldn't need the secondary dish?
Once you get this working, you'll have to set it up as a movable system that always projects to the same point... I can feel the headache coming on already!

I can control the focal length from 8 m to 15 m or more, by turning a bolt located on the lever which pushes the microswitch controlling the vac pump.
But the "focal cloud" is always 4" and more, not concentrated enough to drive directly LNBF (various scalars did not help). That's why I needed secondary reflector.
Really small focal cloud is possible, using precisely made offset big paraboloid, but it is beyond my means...
What puzzles me, is that optically visible 4" focal spot does not define real microwave spot, which seems to be much bigger (despite theory which claims that reflectors are frequency-independent).
I have a few more photos: