Channel master frankensteined

INOX bits and pieces belong to the practical part of the exercise (Part Nr.2), and making them is not a big deal. But more important is Part Nr.1, namely to understand the way how all the parts should be made. :D
 
To align a simple offset antenna (such as Channel Master 1.8m with 22.6* offset angle), you need to make sure it is correctly assembled and LNB's phase center is colocated with the antenna's focal point. In addition, you should make sure LNB is pointed correctly to the proper point on the surface of the dish. It is easy to check, just point your antenna towards your due-south satellite (let s say, your central satellite has 30* elevation above the horizon), get the maximum signal and then measure the leaning of the face of the dish. If the measured angle is 30-22.6=7.4* then the antenna is assembled correctly and pointed properly.
In the case of dual-reflector antenna system (Fibo design), things are getting more difficult. Firstly, the main mirror should be properly pointed towards the satellite. Secondly, the first focal point of the subreflector should be colocated with the main mirror's focal point and should be properly oriented toward the main mirror. Thirdly, the phase center of the LNB should be colocated with the second focal point of the SUB and correctly pointed to the proper point on the surface of the SUB. Sounds like a mathematical task with too many unknowns! Well, the reality might be not so complicated, as manufacturers of the antennas already did their work.... installed LNB correctly on offset antenna. They also fixed the feedhorn and the SUB to the bottom arm of the Fibo antenna.
So, now is the question: How to transform CM 1.8m antenna to dual-reflector system?
Very simple
- you already have antenna pointed towards central satellite;
- remove original feedarms and LNB-holder;
- install new feedarms and Fibo SUB&feedhorn;
- adjust position of the SUB&feedhorn till you get maximum signal.
 
I had a play with this today, some excellent results, a bit more fine tuning to do...20231113_154125.jpg20231113_154155.jpg20231113_154140.jpg
 
loving your spikes - i have never bothered, as i hardly get any bird poo on my dishes
love the mini sat dish at the end of your LNB arm
:)
 
scopus said:
Yes, I'm thinking that myself....
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Could the entire sub-reflector+LNB rotate together on the motor? Though I have a feeling the sub-reflector has to be closer to the dish than other LNBs.

Do you have any signal readings/comparisons?
 
Captain Jack said:
Could the entire sub-reflector+LNB rotate together on the motor? Though I have a feeling the sub-reflector has to be closer to the dish than other LNBs.

Do you have any signal readings/comparisons?
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I think Wim did a LNB motor job on his 1.2 Fibo? I need to find the thread. Not done a great deal of Signal comparisons, but something has changed on the DRHD software, it doesn't seem to go above 15db on the display...A quick grab on on 1W Sky news...Screenshot_20231114-111141_Finder.jpg
 
I just opened your package after four years. It took my 15 minutes of digging in the tube to realise that the caps had screws, which were obscured by the packing tape. On both sides. Then I couldn't pull out the rod from the tube because I also didn't realise that it was screwed to the tube cap itself. Jeebuz @RimaNTSS

That said your workmanship is absolutely top notch. Almost as good as your packing! I will see if I can play with it over the next few weeks. Always time-permitting...
 
Captain Jack said:
I just opened your package after four years. It took my 15 minutes of digging in the tube to realise that the caps had screws, which were obscured by the packing tape. On both sides. Then I couldn't pull out the rod from the tube because I also didn't realise that it was screwed to the tube cap itself. Jeebuz @RimaNTSS

That said your workmanship is absolutely top notch. Almost as good as your packing! I will see if I can play with it over the next few weeks. Always time-permitting...
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It's well worth the effort CJ. One the sub reflector is in the proper phase with the main reflector..boom! Took a bit of tweaking here but more than pleased..
 
Plans are afoot to make this into a muti LNB arrangement. First was to fit the motor and check C Band was OK at focus not using the sub. The plan is to put the sub on the flywheel for Ku as the dual optics yield excellent results..You get the idea...20240207_152519.jpg20240207_152550.jpg20240207_152840.jpg
 
Manikm909 said:
let me know if its still solid signal about 10pm mate...
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Still solid..Just listening to the Stingray music collection of stations..
 
Nice! Are you finding that the dual reflector arrangement is giving better signal over the standard one? Nice results on the C band even with the Ku LNB in the way.
 
Captain Jack said:
Nice! Are you finding that the dual reflector arrangement is giving better signal over the standard one? Nice results on the C band even with the Ku LNB in the way.
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Yes I am CJ. This is a way of doing it without major engineering where the Fibo feedhorn sits. Also I think, I would have too much shadow with a full size horn on the C Band LNB with that arrangement. Unfortunately, I have been snowed off today to do any more outside ...Next is to get the sub reflector on the motor..
 
scopus said:
Yes I am CJ. This is a way of doing it without major engineering where the Fibo feedhorn sits. Also I think, I would have too much shadow with a full size horn on the C Band LNB with that arrangement. Unfortunately, I have been snowed off today to do any more outside ...Next is to get the sub reflector on the motor..
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>> I would have too much shadow with a full size horn on << - - that's another story for another time :p.
 
John said:
>> I would have too much shadow with a full size horn on << - - that's another story for another time :p.
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Ooohheeerrr missus
 
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